Laboratory Title: - Science A 2 Z
The lab directly following, entitled, “Piecing Together the Plates” can be used as a stand alone activity, but would make more sense to the students if it followed a unit/lesson plans on plate tectonics, specifically the different boundary types. For 3 possible lesson plans to incorporate into this unit, please see the following pages after the “Piecing Together the Plates” lesson plan. (The Earth’s Plates, Snack Tectonics, Egg Plates).
Laboratory Title: Piecing Together the Plates
Your Name: Lisa McCready
Concepts Addressed: Tectonic Plates; Continental and Oceanic Plates, Plate Boundaries
Lab Goals: Students will build a knowledge base surrounding the actual plate names and the boundaries located at the edges of the plates
Lab Objectives: Students will…
▪ Identify the world continents and oceans
▪ Provide an example of a world map with their estimation of the location of the 15 major plates
▪ Compare their estimation to the actual plate locations
▪ Predict certain boundary types based on plate tectonic clues
▪ Discuss/share with class/classmates what transpires at the different boundaries
▪ Work cooperatively with partners
SCIENCE Benchmark(s) Addressed (3rd to 4th Grade):
3.1 Structure and Function: Living and non-living things vary in their characteristics and properties.
3.1P.1 Compare and contrast the properties of states of matter.
3.2 Interaction and Change: Living and non-living things interact with energy and forces.
3.2P.1 Describe how forces cause changes in an object’s position, motion, and speed.
3.4 Engineering Design: Engineering design is a process that uses science to solve problems or address needs or aspirations.
3.4D.3 Give examples of inventions that enable scientists to observe things that are too small or too far away.
4.1 Structure and Function: Living and non-living things can be classified by their characteristics and properties.
4.1E.1 Identify properties, uses, and availability of Earth materials.
4.2 Interaction and Change: Living and non-living things undergo changes that involve force and energy.
4.2P.1 Describe physical changes in matter and explain how they occur.
4.2E.1 Compare and contrast the changes in the surface of Earth that are due to slow and rapid
processes.
4.3 Scientific Inquiry: Scientific inquiry is a process of investigation through questioning, collecting, describing, and examining evidence to explain natural phenomena and artifacts.
4.3S.3 Explain that scientific claims about the natural world use evidence that can be confirmed and support a logical argument.
Materials and Costs:
List the consumable supplies and estimated cost for presenting to a class of 30 students
Pencils (.10 x 30) $3.00
Tracing paper (1 answer key per student, pack of 40 sheets for 2.99) $2.99
Tape (A couple of rolls, the students can share/pass around, 2.08 x 3) $6.24
Paper – World Continents and Oceans map (I bought preprinted packet, 50
sheets) $6.99
Paper – Naming your Plates Activity (.01 x 30) $0.30
Paper – What’s Going on at Some of Our Borders Activity (.01 x 30) $0.30
Paper – Create Your Own Phrase Activity (.01 x 30) $0.30
Paper – Test Your Plate Knowledge Activity (4 pages per student, .01 x 120 $1.20
Paper – Quiz (.01 x 30) $0.30
Estimated total, one-time, start-up cost: $21.62
**If I had more money, or was an actual teacher and would be doing this activity multiple times, I would create the answer keys on transparency/overhead paper instead of tracing paper. This would allow a one time building of an answer key and photocopying it onto the transparency paper. Those answer keys could then be used over and over and could be written on with dry erase pens!
Time:
Initial Preparation time: Teacher has to create an outline of plates based on map you are using as background, then, trace an answer key for each student. Buy supplies. Make copies.
60 – 90 minutes
Preparation time: Getting supplies together.
10 minutes
Instruction time: This depends on what activities you want to include.
30 minutes
Clean-up time:
5 minutes
Assessment (include all assessment materials):
1. Name 2 continental plates and their approximate location.
2. Draw/sketch a plate boundary type and write its name and a landform or geological activity that can occur there.
3. What was the most interesting thing you learned during this unit?
ACTIVITY INSTRUCTIONS (Based on a 30 minute timeframe):
1. Introduce information to class. (Via PowerPoint). Approximately 5 minutes.
2. Briefly describe to the class what the complete activity will be and then provide guidance as the students work through the different parts of the activity.
3. Provide each student with a pencil.
4. Hand out the blank “World Continents and Oceans” paper.
5. Have the students label the continents and oceans.
6. Have the students draw, using a pencil, on their map what they think the plate boundaries are for the 15 plates being studied. Emphasize that it does not matter how close they are, it is just to get an idea of where they think the boundaries lie on our Earth. You can suggest that they number their plates so they can tell if they have mapped 15 of them. Approximately 3 minutes.
7. Have the students raise their hand when they are done and then provide them with an outline (transparency) to place over their maps to show them the real plate boundaries. They will also be given the next activity (NAMING YOUR PLATES). Tell the students that they should feel free to work with a partner to work through the rest of the activities. Approximately 3 minutes.
8. Walk around the classroom as the students are working through their activities to make sure they understand what they are doing and that they stay on task.
9. Have the students raise their hands as they finish the activities.
10. Hand out the “WHAT’S GOING ON AT SOME OF OUR BORDERS” activity. Approximately 3 minutes.
11. Hand out the “CREATE YOUR OWN PHRASE TO REMEMBER THE NAMES OF THE PLATES” activity. Approximately 5 minutes.
12. End activity with a review which must include (Done via PowerPoint, approximately 5 minutes):
a. Master map showing the students the names of the plates so they can compare their map to the answer key.
b. Show on the map the 3 boundaries they were to figure out and discuss as a group the correct answers.
c. Allow students to share their “phrases” they came up with to remember the names of the plates.
d. QUESTIONS!
Naming Your Plates
While there are more than 15 plates, we are focusing on 15 of the most common continental and oceanic plates.
Using the clues below, write the names of the plates on your transparency!
1. African – This plate covers more than just the continent of Africa.
2. Antarctic – This plate is the 5th largest plate in the world and is in the Southern Hemisphere.
3. Arabian – This plate is mainly covering the Arabian Peninsula.
4. Australian – This plate covers more than just the continent of Australia.
5. Caribbean – This plate is mostly oceanic and is touching the southern end of the plate which covers the continent on which we live.
6. Cocos – This is an oceanic plate and likes to snuggle up next to the Caribbean plate.
7. Eurasian – This is a tectonic plate that covers two continents, whose names can be figured out by breaking apart the name of the tectonic plate.
8. Indian – This plate covers the country of the same name, minus an “n.”
9. Juan De Fuca – This plate is very small and is located along the western coast of our country.
10. Nazca – This is an oceanic plate. Its northern border touches the Cocos plate southern border.
11. North America – YOU LIVE HERE! It gets labeled 2 times on your map.
12. Pacific – This is an oceanic plate. It gets labeled 3 times on your map.
13. Philippine – This plate is in between the Pacific plate and the Eurasian plate.
14. Scotia – This is an oceanic plate in the southern hemisphere and touches the 5th largest plate in the world.
15. South American – This plate is between the African and Nazca plates.
What’s Going on at Some of Our Borders?
Remember the names of our tectonic plate boundaries…
Convergent
Divergent
Transform
1. The following landform is along the border of the South American plate and the African plate:
• A portion of the Mid Atlantic Ridge
Using this information, please make note on your transparency along the border between the South American and African Plate, as to the type of boundary.
2. The following tectonic activity and landforms have been created along the border between the Juan de Fuca plate and the North American plate:
• Subduction
• Cascade Range Volcanoes
• Pacific Ring of Fire
Using this information, please make note on your transparency along the border between the Juan de Fuca plate and the North American plate, as to the type of boundary.
3. Located in California, as part of the North American Plate, the following can be found:
• San Andreas Fault
• Earthquakes
Using this information, please make note on your transparency somewhere in the vicinity of California, as to the type of boundary.
Create Your Own Way To Remember the Names of the Plates!
Use the following information to come up with a phrase, a song, or something with meaning to you, to help you remember the names of the 15 most common plates!
MAJOR:
African, Antarctic, Australian, Eurasian, Indian, North American, Pacific, South American
MINOR:
Arabian, Caribbean, Cocos, Juan de Fuca, Nazca, Philippine, Scotia
7 CONTINENTS:
North America, South America, Africa, Europe, Asia, Australia, Antarctica
The following websites can be used as a reference for material to use in lectures, lesson plans, visuals, videos, etc, associated with Plate Tectonics/Continental Plates. Many of the websites contain the same information, but different people retain and digest information in different ways, so these websites should give you a great variety of ways to understand the information yourself and a variety of ways to share it with your students.
Books Referenced:
Bower, Sue., Restless Earth, A Beginner’s Guide to Plate Tectonics, DK Essential Science, New York, 16-37 pp., 2002.
Following is information about the 15 plates covered in this lesson plan. I used this information, along with a map of the plates, to come up with my questions on the worksheet, “Naming Your Plates.” The information can be used in other ways to supplement your individual needs/lecture. The information came from Wikipedia. The link can be found at the end of the data.
[pic]
Image above:
The African Plate is a tectonic plate which includes the continent of Africa, as well as oceanic crust which lies between the continent and various surrounding ocean ridges.
The westerly side is a divergent boundary with the North American Plate to the north and the South American Plate to the south forming the central and southern part of the Mid-Atlantic Ridge. The African plate is bounded on the northeast by the Arabian Plate, the southeast by the Indo-Australian Plate, the north by the Eurasian Plate and the Anatolian Plate, and on the south by the Antarctic Plate. All of these are divergent or spreading boundaries with the exception of the northern boundary with the Eurasian Plate (except for a short segment near the Azores, the Terceira Rift).
The African Plate's speed is estimated at around 2.15 centimeters per year. It has been moving over the past 100 million years or so in a general northeast direction. This is drawing it closer to the Eurasian Plate, causing subduction where oceanic crust is converging with continental crust (e.g. portions of the central and eastern Mediterranean).
The Antarctic Plate is a tectonic plate covering the continent of Antarctica and extending outward under the surrounding oceans. The Antarctic Plate has a boundary with the Nazca Plate, the South American Plate, the African Plate, the Indo-Australian Plate, the Scotia Plate and a divergent boundary with the Pacific Plate forming the Pacific-Antarctic Ridge.
The Antarctic plate is roughly 60,900,000 square kilometers[1]. It is the fifth biggest plate in the world.
The Antarctic plate movement is estimated at least 1 centimeter/per year towards the Atlantic Ocean.
The Arabian Plate is one of three tectonic plates (the African, Arabian and Indian crustal plates) which have been moving northward over millions of years toward an inevitable collision with Eurasia. This is resulting in a mingling of plate pieces and mountain ranges extending in the west from the Pyrenees, crossing southern Europe and the Middle East, to the Himalayas and ranges of southeast Asia. [1]
The Arabian Plate consists mostly of the Arabian peninsula; it extends northward to Turkey. The plate borders are:
• East, with the Indo-Australian Plate
• South, with the African Plate to the west and the Indo-Australian Plate to the east
• West, a left lateral fault boundary with the African Plate called the Dead Sea Transform (DST), and a divergent boundary with the African Plate called the Red Sea Rift which runs the length of the Red Sea;
• North, complex convergent boundary with the Anatolian Plate and Eurasian Plate.
The Arabian Plate was part of the African plate during much of the Phanerozoic Eon (Paleozoic - Cenozoic), until the Oligocene Epoch of the Cenozoic Era. Red Sea rifting began in the Eocene, but the separation of Africa and Arabia occurred in the Oligocene, and since then the Arabian Plate has been slowly moving toward the Eurasian Plate.
The collision between the Arabian Plate and Eurasia is pushing up the Zagros Mountains of Iran.
The Indo-Australian Plate is a major tectonic plate that includes the continent of Australia and surrounding ocean, and extends northwest to include the Indian subcontinent and adjacent waters. Recent studies suggest that the Indo-Australian Plate may be in the process of breaking up into two separate plates due primarily to stresses induced by the collision of the Indo-Australian Plate with Eurasia along the Himalayas. [1] The two protoplates or subplates are generally referred to as the Indian Plate and the Australian Plate.
India, Meganesia (Australia, New Guinea, and Tasmania), New Zealand, and New Caledonia are all fragments of the ancient supercontinent of Gondwana. Seafloor spreading separated these land masses from one another, but as the spreading centers became inactive they fused into a single plate.
Recent GPS measurement in Australia confirms the plate's movement as being 35 degrees east of north with a velocity of 67 mm/yr. Note also the same directions and velocities for points at Auckland, Christmas Island and southern India. The slight change in direction at Auckland is presumably due to a slight buckling of the plate there, where it is being compressed by the Pacific Plate.
The southeasterly side is a complex but generally convergent boundary with the Pacific Plate. The Pacific Plate subducting under the Australian Plate forms the Tonga and Kermadec Trenches, and the parallel Tonga and Kermadec island arcs. It has also uplifted the eastern parts of New Zealand's North Island.
The continent of Zealandia, which separated from Australia 85 million years ago and stretches from New Caledonia in the north to New Zealand's subantarctic islands in the south, is now being torn apart along the transform boundary marked by the Alpine Fault.
South of New Zealand the boundary becomes a transitional transform-convergent boundary, the Macquarie Fault Zone, where the Australian Plate is beginning to subduct under the Pacific Plate along the Puysegur Trench. Extending southwest of this trench is the Macquarie Ridge.
The southerly side is a divergent boundary with the Antarctic Plate called the Southeast Indian Ridge (SEIR). The westerly side is a transform boundary with the Arabian Plate called the Owen Fracture Zone, and a divergent boundary with the African Plate called the Central Indian Ridge (CIR). The northerly side of the Indo-Australian Plate is a convergent boundary with the Eurasian Plate forming the Himalaya and Hindu Kush mountains.
The northeast side of the Indo-Australian plate forms a subducting boundary with the Eurasian plate on the borders of the Indian Ocean from Bangladesh, to Myanmar (formerly Burma) to the south-west of Indonesian islands of Sumatra and Borneo.
The subducting boundary through Indonesia is not parallel to the biogeographical Wallace line that separates the indigenous fauna of Asia from that of Australasia: the Eastern islands of Indonesia lie mainly on the Eurasian Plate, but have Australasian-related fauna and flora.
The Caribbean Plate is a mostly oceanic tectonic plate underlying Central America and the Caribbean Sea off the north coast of South America.
Roughly 3.2 million square kilometers (1.2 million square miles) in area, the Caribbean Plate borders the North American Plate, the South American Plate, the Nazca Plate and the Cocos Plate. These borders are regions of intense seismic activity, including frequent earthquakes, occasional tsunamis,[1] and volcanic eruptions.
The northern boundary with the North American plate is a transform or strike-slip boundary which runs from the border area of Belize, Guatemala (Motagua Fault), and Honduras in Central America, eastward through the Cayman trough on south of the southeast coast of Cuba, and just north of Hispaniola, Puerto Rico, and the Virgin Islands. Part of the Puerto Rico Trench, the deepest part of the Atlantic Ocean (roughly 8,400 meters), lies along this border. The Puerto Rico trench is at a complex transition from the subduction boundary to the south and the transform boundary to the west.
The eastern boundary is a subduction zone, but since the boundary between the North and South American Plates in the Atlantic is as yet undefined, it is unclear which one, or possibly both, is descending under the Caribbean Plate. Subduction forms the volcanic islands of the Lesser Antilles island arc from the Virgin Islands in the north to the islands off the coast of Venezuela in the south. This boundary contains seventeen active volcanoes, most notably Soufriere Hills on Montserrat, Mount Pelée on Martinique, La Grande Soufrière on Guadeloupe, Soufrière Saint Vincent on Saint Vincent, and the submarine volcano Kick-'em-Jenny which lies about 10 km north of Grenada.
Along the geologically complex southern boundary the Caribbean Plate interacts with the South American Plate forming Barbados, Trinidad (both on the South American Plate) and Tobago (on the Caribbean Plate), and islands off the coast of Venezuela (including the Leeward Antilles) and Colombia. This boundary is in part the result of transform faulting along with thrust faulting and some subduction. The rich Venezuelan petroleum fields possibly result from this complex plate interaction.
The western portion of the plate is occupied by Central America. The Cocos Plate in the Pacific Ocean is subducted beneath the Caribbean Plate, just off the western coast of Central America. This subduction forms the volcanoes of Guatemala, El Salvador, Nicaragua, and Costa Rica, also known as the Central America Volcanic Arc.
The Cocos Plate is an oceanic tectonic plate beneath the Pacific Ocean off the west coast of Central America, named for Cocos Island, which rides upon it.
The Cocos Plate is created by sea floor spreading along the East Pacific Rise and the Cocos Ridge, specifically in a complicated area geologists call the Cocos-Nazca spreading system. From the rise the plate is pushed eastward and pushed or dragged (perhaps both) under the less dense overriding Caribbean Plate, in the process called subduction. The subducted leading edge heats up and adds its water to the mantle above it. In the mantle layer called the asthenosphere, mantle rock melts to make magma, trapping superheated water under great pressure. As a result, to the northeast of the subducting edge lies the continuous arc of volcanos stretching from Costa Rica to Guatemala and a belt of earthquakes that extends farther north, into Mexico.
The northern boundary of the Cocos Plate is the Middle America Trench. The eastern boundary is a transform fault, the Panama Fracture Zone. The southern boundary is a mid-oceanic ridge, the Galapagos Rise.[1] The western boundary is another mid-ocean ridge, the East Pacific Rise.
The Cocos and Nazca Plates are the remnants of the former Farallon Plate, which broke up about 23 million years ago. A hotspot under the Galapagos Islands lies along the Galapagos Rise. (see Galapagos hotspot)
The Rivera Plate north of the Cocos Plate, is thought to have separated from the Cocos Plate 5-10 million years ago. The boundary between the two plates appears to lack a definite transform fault, yet they are regarded as distinct.
The devastating 1985 Mexico City earthquake was a result of the subduction of the Cocos Plate beneath the North American Plate.
The Eurasian Plate is a tectonic plate which includes most of the continent of Eurasia (a landmass consisting of the traditional continents of Europe and Asia), with the notable exceptions of the Indian subcontinent, the Arabian subcontinent, and the area east of the Chersky Range in East Siberia. It also includes oceanic crust extending westward to the Mid-Atlantic Ridge and northward to the Gakkel Ridge.
The easterly side is a boundary with the North American Plate to the north and a boundary with the Philippine Mobile Belt and the Philippine Sea Plate to the south, and possibly with the Okhotsk Plate and the Amurian Plate. The southerly side is a boundary with the African Plate to the west, the Arabian Plate in the middle and the Indo-Australian Plate to the east. The westerly side is a convergent boundary with the North American Plate forming the northernmost part of the Mid-Atlantic Ridge, which is straddled by Iceland. The 1973 eruption of Eldfell, the volcano of the Icelandic island Heimaey, caused by the North American and the Eurasian plates pulling apart, is an example of a constructive plate boundary.
The India or Indian Plate is a tectonic plate that was originally a part of the ancient continent of Gondwanaland from which it split off, eventually becoming a major plate. About 50 to 55 million years ago, it fused with the adjacent Australian Plate. It is today part of the major Indo-Australian Plate, and includes the subcontinent of India and a portion of the basin under the Indian Ocean.
In the late Cretaceous Period about 90 million years ago, subsequent to the splitting off from Gondwanaland of conjoined Madagascar and India, the India Plate split from Madagascar. It began moving north, at about 20 cm/yr (8 in/yr) [1], and began colliding with Asia between 50 and 55 million years ago, in the Eocene epoch of the Cenozoic Era. During this time, the India Plate covered a distance of 2,000 to 3,000 km (1,200 to 1,900 mi), and moved faster than any other known plate. In 2007, German geologists determined that the reason the India Plate moved so quickly is that it is only half as thick as the other plates which formerly constituted Gondwanaland.[1]
The collision with the Eurasian Plate along the boundary between India and Nepal formed the orogenic belt that created the Tibetan Plateau and the Himalaya Mountains, as sediment bunched up like earth before a plow.
The India Plate is currently moving northeast at 5 cm/yr (2 in/yr), while the Eurasian Plate is moving north at only 2 cm/yr (0.8 in/yr). This is causing the Eurasian Plate to deform, and the India Plate to compress at a rate of 4 mm/yr (0.15 in/yr).
The Juan de Fuca Plate, named after the explorer, is a tectonic plate arising from the Juan de Fuca Ridge, and subducting under the northerly portion of the western side of the North American Plate at the Cascadia subduction zone. It is bounded on the south by the Blanco Fracture Zone, on the north by the Nootka Fault, and along the west by the Pacific Plate. The Juan de Fuca Plate was originally part of the once-vast Farallon Plate, now largely subducted under the North American Plate, and has since fractured into three pieces. The plate name is in some references applied to the entire plate east of the undersea spreading zone, and in other references only to the central piece. When so distinguished, the piece to the south is known as the Gorda Plate and the piece to the north is known as the Explorer Plate. The separate pieces are demarcated by the large offsets of the undersea spreading zone manifested in the above mentioned fracture zone and fault.
This subducting plate system has formed the volcanic Cascade Range, the Cascade Volcanoes and the Pacific Ranges, which is part of the Pacific Ring of Fire, along the west coast of North America from southern British Columbia to northern California.
The last major earthquake at the Cascadia subduction zone was the 1700 Cascadia earthquake, estimated to have a moment magnitude of 8.7 to 9.2. Based on carbon dating of local tsunami deposits, it occurred around 1700. As reported in National Geographic on December 8, 2003, Japanese tsunami records indicate the quake happened the evening of Tuesday, January 26, 1700.
In 2008, small earthquakes were observed within the plate. The unusual quakes were described as "more than 600 quakes over the past 10 days in a basin 150 miles southwest of Newport." The quakes were unlike most quakes in that they did not follow the pattern of a large quake, followed by smaller aftershocks; rather, they were simply a continual deluge of small quakes. Furthermore, they did not occur on the tectonic plate boundary, but rather in the middle of the plate. The subterranean quakes were heard on hydrophones, and scientists described the sounds as similar to thunder, and unlike anything heard previously.[1]
The Nazca Plate, named after the Nazca region of southern Peru, is an oceanic tectonic plate in the eastern Pacific Ocean basin off the west coast of South America.
The eastern margin is a convergent boundary subduction zone under the South American Plate and the Andes Mountains, forming the Peru-Chile Trench. The southern side is a divergent boundary with the Antarctic Plate, the Chile Rise, where seafloor spreading permits magma to rise. The western side is a divergent boundary with the Pacific Plate, forming the East Pacific Rise. The northern side is a divergent boundary with the Cocos Plate, the Galapagos Rise. A triple junction occurs at the northwest corner of the plate where the Nazca, the Cocos, and the Pacific plates all join off the coast of Colombia.
A second junction, the Chile Triple Junction, occurs at the southwest corner at the intersection with the Nazca, the Pacific, and the Antarctic plates off the coast of southern Chile. At each of these triple junctions an anomalous microplate exists, the Galapagos Microplate at the northern junction and the Juan Fernandez Microplate at the southern junction. The Easter Island Microplate is a third microplate that is located just north of the Juan Fernandez Microplate and lies just west of Easter Island.
Yet another triple junction, the Chile Triple Junction,[1] occurs on the seafloor of the Pacific Ocean off Taitao and Tres Montes Peninsula at the southern coast of Chile. Here three tectonic plates meet: the Nazca Plate, the South American Plate, and the Antarctic Plate. This triple junction is unusual in that it consists of a mid-oceanic ridge, the Chile Rise, being subducted under the South American Plate at the Peru-Chile Trench. This triple junction has been considered to be related to the moment magnitude 9.5, 1960 megathrust earthquake known as the Great Chilean Earthquake.
Luckily, very few islands are there to suffer the earthquakes that are a result of complicated movements at these junctions. Juan Fernández Islands is an exception.
The Carnegie Ridge is a 1350-km-long and up to 300-km-wide feature on the ocean floor of the northern Nazca Plate that includes the Galápagos archipelago at its western end. It is being subducted under South American with the rest of the Nazca Plate.
The absolute motion of the Nazca Plate has been calibrated at 3.7 cm/yr east motion (88°), some of the fastest absolute motion of any tectonic plate. The subducting Nazca Plate, which exhibits unusual flat-slab subduction, is tearing as well as deforming as it is subducted (Barzangi and Isacks). The subduction has formed, and continues to form the volcanic Andes Mountain Range. Deformation of the Nazca Plate even affects the geography of Bolivia, far to the east (Tinker et al.).
The precursor of the Nazca Plate and the Cocos Plate to its north was the Farallon Plate, which split in late Oligocene times, about 22.8 Mya, a date arrived at by interpreting magnetic anomalies.
The North American Plate is a tectonic plate covering most of North America, Greenland and parts of Siberia and Iceland. It extends eastward to the Mid-Atlantic Ridge and westward to the Chersky Range in eastern Siberia. The plate includes both continental and oceanic crust. The interior of the main continental landmass includes an extensive granitic core called a craton. Along most of the edges of this craton are fragments of crustal material called terranes, accreted to the craton by tectonic actions over the long span of geologic time. It is believed that much of North America west of the Rockies is composed of such terranes.
For the most part, the North American Plate moves in roughly a southwest direction away from the Mid-Atlantic Ridge.
The motion of the plate cannot be driven by subduction as no part of the North American Plate is being subducted, except for a very small section comprising part of the Puerto Rico Trench; thus other mechanisms continue to be investigated.
One recent study suggests that a mantle convective current is propelling the plate. [4]
The easterly side of the North American Plate is a divergent boundary with the Eurasian Plate to the north and the African Plate to the south forming the northern part of the Mid-Atlantic Ridge.
The southerly boundary with the Cocos Plate to the west and the Caribbean Plate to the east is a transform fault, represented by the Cayman Trench under the Caribbean Sea and the Motagua Fault through Guatemala.
The rest of the southerly margin which extends east to the Mid Atlantic Ridge and marks the boundary between the North American Plate and the South American Plate remains poorly understood and undefined. The westerly boundary is the Queen Charlotte Fault running offshore along the coast of Alaska and the Cascadia subduction zone to the north, the San Andreas Fault through California, the East Pacific Rise in the Gulf of California, and the Middle America Trench to the south.
On the northerly boundary is a continuation of the Mid-Atlantic ridge called the Gakkel Ridge. The rest of the boundary in the far northwestern part of the plate extends into Siberia. This boundary continues from the end of the Gakkel Ridge as the Laptev Sea Rift, on to a transitional deformation zone in the Chersky Range, then the Ulakhan Fault, and finally the Aleutian Trench to the end of the Queen Charlotte Fault system.
On its western edge the Farallon Plate has been subducting under the North American Plate since the Jurassic period. The Farallon Plate has almost completely subducted beneath the western portion of the North American Plate leaving that part of the North American Plate in contact with the Pacific Plate as the San Andreas Fault. The Juan de Fuca, Cocos, and Nazca Plates are remnants of the Farallon Plate.
The boundary along the Gulf of California has not yet been clearly described and research is ongoing. The Gulf is underlain by the northern end of the East Pacific Rise. West of the Rise is the Pacific Plate. East of the Rise, most tectonic maps show the North American Plate.
It is generally accepted that a piece of the North American Plate was broken off and transported north as the East Pacific Rise propagated northward, creating the Gulf of California. However, it is as yet unclear whether the oceanic crust east of the Rise and west of the mainland coast of Mexico is actually a new plate beginning to converge with the North American Plate, consistent with the standard model of rift zone spreading centers generally.
The Pacific Plate is an oceanic tectonic plate beneath the Pacific Ocean.
To the north the easterly side is a divergent boundary with the Explorer Plate, the Juan de Fuca Plate and the Gorda Plate forming respectively the Explorer Ridge, the Juan de Fuca Ridge and the Gorda Ridge. In the middle the easterly side is a transform boundary with the North American Plate along the San Andreas Fault and a boundary with the Cocos Plate. To the south the easterly side is a divergent boundary with the Nazca Plate forming the East Pacific Rise.
The southerly side is a divergent boundary with the Antarctic Plate forming the Pacific-Antarctic Ridge.
The westerly side is a convergent boundary subducting under the Eurasian Plate to the north and the Philippine Plate in the middle forming the Mariana Trench. In the south, the Pacific Plate has a complex but generally convergent boundary with the Indo-Australian Plate, subducting under it north of New Zealand forming the Tonga Trench and the Kermadec Trench. The Alpine Fault marks a transform boundary between the two plates, and further south the Indo-Australian Plate subducts under the Pacific Plate forming the Puysegur Trench. The part of Zealandia to the east of this boundary is the plate's largest block of continental crust.
The northerly side is a convergent boundary subducting under the North American Plate forming the Aleutian Trench and the corresponding Aleutian Islands.
The Pacific Plate contains an interior hot spot forming the Hawaiian Islands.
It is believed that the Pacific Plate is moving in unison with the minor, Bird's Head Plate.
The Philippine Sea Plate is a tectonic plate beneath the Pacific Ocean to the east of the Philippines. The Philippine Sea Plate comprises oceanic lithosphere that lies beneath the Philippine Sea, and so has been referred to in the scientific literature of the last 50 years as the Philippine Sea Plate.
Most segments of the Philippines, including northern Luzon, are part of the Philippine Mobile Belt, which is separate from the Sunda Plate to the southwest, the South China Sea Plate to the west and north-west, Taiwan to the north, and the Philippine Sea Plate to the east. Although parts of the Republic of the Philippines, Palawan with the Calamian Islands, plus the Sulu Archipelago with the Zamboanga Peninsular of western Mindanao, are the tops of two protruding north-eastern arms of the Sunda Plate. They are in collision with the Philippine Mobile Belt.
The Philippine Sea Plate is demarkated on the west by the Philippine Trench and the East Luzon Trench, bounded by Taiwan and the Ryukyu islands to the northwest, Japan to the north, the Izu-Ogasawara (Bonin) and Mariana Islands to the east, and Yap, Palau, and the north-easternmost part of Indonesia, Halmahera to the south. The eastern part of the plate is occupied by the Izu-Bonin-Mariana Arc system and bounded by the Mariana Plate.
The easterly side of the Philippine Sea Plate is a convergent boundary with the subducting Pacific Plate. The Philippine Sea Plate is subducted on the west under the Philippine Mobile Belt, and bounded on the south by the Caroline Plate and Bird's Head Plate, on the north by the North American Plate (or the Okhotsk Plate) and possibly by the Amurian Plate.
Subduction of the Philippine Sea Plate under remnants of the Eurasian Plate, plus break-away parts of the Philippine Sea Plate formed the Philippine Mobile Belt and Taiwan, and induced the volcanic activity on the eastern side of the Philippine Mobile Belt. This subduction and volcanic activity is ongoing.
In the northernmost part of the plate, thickened crust of the Izu-Bonin-Mariana arc is colliding with Japan constituting the Izu Collision Zone.
The Izu Peninsula is the northernmost tip of the Philippine Sea Plate. The Philippine Sea Plate, the Eurasian Plate (or the Amurian Plate), and the North American (or Okhotsk Plate) meet at Mount Fuji.
The Scotia Plate is an oceanic tectonic plate bordering the South American Plate on the north, the South Sandwich Plate to the east, and the Antarctic Plate on the south and west.
The north and south boundaries of the plate are transform fault boundaries. At the eastern margin the Scotia has a spreading boundary between it and the small South Sandwich Plate. The South American Plate is subducting under east side of the South Sandwich Plate, which is thought to have brought about its separation from the Scotia Plate, starting as backarc spreading. The western boundary with the Antarctic plate is a complex and rather ill-defined boundary.
There is some speculation that the westward motion of the South American Plate may have forced the Caribbean and Scotia Plates at its northern and southern ends respectively to squeeze around it. Both share a similar shape and are bounded along their eastern side by a subducting part of the South American Plate. [1]
The South American Plate is a tectonic plate covering the continent of South America and extending eastward to the Mid-Atlantic Ridge.
The easterly side is a divergent boundary with the African Plate forming the southern part of the Mid-Atlantic Ridge. The southerly side is a complex boundary with the Antarctic Plate and the Scotia Plate. The westerly side is a convergent boundary with the subducting Nazca Plate. The northerly side is a boundary with the Caribbean Plate. At the Chile Triple Junction in Taitato-Tres Montes Peninsula an oceanic ridge, the Chile Rise, is subducting under the South American plate.
The remains of the Farallon Plate, split into the current Cocos Plate and Nazca Plate are still subducting under the western edge of the South American Plate. This subduction is responsible for lifting the massive Andes Mountains and causing the volcanos which are strewn throughout them.
Major plates
• African Plate
• Antarctic Plate
• Arabian Plate
• Australian Plate
• Caribbean Plate
• Cocos Plate
• Eurasian Plate
• Indian Plate
• Juan de Fuca Plate
• Nazca Plate
• North American Plate
• Pacific Plate
• Philippine Sea Plate
• Scotia Plate
• South American Plate
[edit] Minor plates
• Aegean Sea Plate
• Altiplano Plate
• Amurian Plate
• Anatolian Plate
• Apulian Plate
• Balmoral Reef Plate
• Banda Sea Plate
• Bird's Head Plate
• Burma Plate
• Caroline Plate
• Conway Reef Plate
• Easter Plate
• Futuna Plate
• Galapagos Plate
• Halmahera Plate
• Hellenic Plate
• Iranian Plate
• Jan Mayen Plate
• Juan Fernandez Plate
• Kermadec Plate
• Kula Plate
• Manus Plate
• Maoke Plate
• Mariana Plate
• Molucca Sea Plate
• New Hebrides Plate
• Niuafo'ou Plate
• North Andes Plate
• North Bismarck Plate
• Okhotsk Plate
• Okinawa Plate
• Panama Plate
• Philippine Microplate
• Rivera Plate
• Sangihe Plate
• South Sandwich Plate
• Shetland Plate
• Solomon Sea Plate
• Somali Plate
• South Bismarck Plate
• Sunda Plate
• Timor Plate
• Tonga Plate
• Woodlark Plate
• Yangtze Plate
[edit] Plates within orogens
Some models identify more minor plates within current orogens.
• Apulian Plate
• Explorer Plate
• Gorda Plate
[edit] Ancient plates
• Baltic Plate
• Bellingshausen Plate
• Charcot Plate
• Cimmerian Plate
• Farallon Plate
• Insular Plate
• Intermontane Plate
• Izanagi Plate
• Lhasa Plate
• Moa Plate
• Phoenix Plate
Notes from PowerPoint presentation used to guide lecture/conversation.
Activity/Landforms found at CONVERGENT BOUNDARIES:
When two plates collide (at a convergent plate boundary), some crust is destroyed in the impact and the plates become smaller. The results differ, depending upon what types of plates are involved.
Oceanic Plate and Continental Plate - When a thin, dense oceanic plate collides with a relatively light, thick continental plate, the oceanic plate is forced under the continental plate; this phenomenon is called subduction.
Two Oceanic Plates - When two oceanic plates collide, one may be pushed under the other and magma from the mantle rises, forming volcanoes in the vicinity.
Two Continental Plates - When two continental plates collide, mountain ranges are created as the colliding crust is compressed and pushed upwards.
Activity/Landforms found at DIVERGENT BOUNDARIES:
Seafloor spreading is the movement of two oceanic plates away from each other (at a divergent plate boundary), which results in the formation of new oceanic crust (from magma that comes from within the Earth's mantle) along a mid-ocean ridge. Where the oceanic plates are moving away from each other is called a zone of divergence. Ocean floor spreading was first suggested by Harry Hess and Robert Dietz in the 1960's.
In plate tectonics, a divergent boundary or divergent plate boundary (also known as a constructive boundary or an extensional boundary) is a linear feature that exists between two tectonic plates that are moving away from each other. These areas can form in the middle of continents but eventually form ocean basins. Divergent boundaries within continents initially produce rifts which produce rift valleys. Therefore, most active divergent plate boundaries are between oceanic plates and are often called mid-oceanic ridges. Divergent boundaries also form Volcanic Islands which occur when the plates move apart to produce gaps which molten lava rises to fill. Thus creating a shield volcano which would eventually build up to become a volcanic island.
Activity/Landforms found at TRANSFORM BOUNDARIES:
Also called “TRANSFORM FAULT, LATERAL SLIPPING, STRIKE SLIP, CONSERVATIVE PLATE BOUNDARY”
When two plates move sideways against each other (at a transform plate boundary), there is a tremendous amount of friction which makes the movement jerky. The plates slip, then stick as the friction and pressure build up to incredible levels. When the pressure is released suddenly, and the plates suddenly jerk apart, this is an earthquake.
If this brings up faults…Normal, Reverse, Strike-Slip – PRINT OUT LAB DRAWINGS AND DRAW ON CHALKBOARD
What is a tectonic plate?
A tectonic plate (also called lithospheric plate) is a massive, irregularly shaped slab of solid rock, generally composed of both continental and oceanic lithosphere. Plate size can vary greatly, from a few hundred to thousands of kilometers across; the Pacific and Antarctic Plates are among the largest. Plate thickness also varies greatly, ranging from less than 15 km for young oceanic lithosphere to about 200 km or more for ancient continental lithosphere (for example, the interior parts of North and South America).
How do these massive slabs of solid rock float despite their tremendous weight? The answer lies in the composition of the rocks. Continental crust is composed of granitic rocks which are made up of relatively lightweight minerals such as quartz and feldspar. By contrast, oceanic crust is composed of basaltic rocks, which are much denser and heavier. The variations in plate thickness are nature's way of partly compensating for the imbalance in the weight and density of the two types of crust. Because continental rocks are much lighter, the crust under the continents is much thicker (as much as 100 km) whereas the crust under the oceans is generally only about 5 km thick. Like icebergs, only the tips of which are visible above water, continents have deep "roots" to support their elevations.
The theory of plate tectonics (meaning "plate structure") was developed in the 1960's. This theory explains the movement of the Earth's plates (which has since been documented scientifically) and also explains the cause of earthquakes, volcanoes, oceanic trenches, mountain range formation, and many other geologic phenomenon. The plates are moving at a speed that has been estimated at 1 to 10 cm per year. Most of the Earth's seismic activity (volcanoes and earthquakes) occurs at the plate boundaries as they interact.
The top layer of the Earth's surface is called the crust (it lays on top of the plates). Oceanic crust (the thin crust under the oceans) is thinner and denser than continental crust. Crust is constantly being created and destroyed; oceanic crust is more active than continental crust.
Under the crust is the rocky mantle, which is composed of silicon, oxygen, magnesium, iron, aluminum, and calcium. The upper mantle is rigid and is part of the lithosphere (together with the crust). The lower mantle flows slowly, at a rate of a few centimeters per year. The asthenosphere is a part of the upper mantle that exhibits plastic properties. It is located below the lithosphere (the crust and upper mantle), between about 100 and 250 kilometers deep.
ADDITIONAL LESSON PLAN IDEA, COURTESY OF BARBARA SHAW, TAUGHT DURING GEOSCIENCE FOR ELEMENTARY EDUCATORS, PSU, SPRING 09:
Laboratory Title (9): The Earth’s Plates
Your Name: Lisa McCready
Concepts Addressed: Plate Tectonics; faults
Lab Goals: Students will explore how the Earth’s plates move and cause formations
Lab Objectives:
▪ Students will visualize plate motions and faulting, using foam model pieces
▪ Students will describe plate motions and faulting
Benchmark(s) Addressed (4th/5th grade):
4.1 Structure and Function: Living and non-living things can be classified by their characteristics and properties.
4.1P.1 Describe the properties of forms of energy and how objects vary in the extent to which they absorb, reflect, and conduct energy.
4.1E.1 Identify properties, uses, and availability of Earth materials.
4.2 Interaction and Change: Living and non-living things undergo changes that involve force and energy.
4.2P.1 Describe physical changes in matter and explain how they occur.
4.2L.1 Describe the interactions of organisms and the environment where they live.
4.2E.1 Compare and contrast the changes in the surface of Earth that are due to slow and rapid processes.
4.3 Scientific Inquiry: Scientific inquiry is a process of investigation through questioning, collecting, describing, and examining evidence to explain natural phenomena and artifacts.
4.3S.3 Explain that scientific claims about the natural world use evidence that can be confirmed and support a logical argument.
5.2 Interaction and Change: Force, energy, matter, and organisms interact within living and non-living systems.
5.2P.1 Describe how friction, gravity, and magnetic forces affect objects on or near Earth.
Materials and Costs:
List the equipment and non-consumable material and estimated cost of each
Metric ruler (1 per group, groups of 3, 10 groups, .79 x 10) $7.90
Estimated total, one-time, start-up cost: $7.90
List the consumable supplies and estimated cost for presenting to a class of 30 students
Foam-Open cell (12 pieces=29.81) $59.62
Felt pens (2 per group, 1.15 x 20) $23.00
Manila folders/Thin poster board (box of 100) $11.99
Rubber cement (1.99 each) $19.90
Foam-Closed cell (12 pieces=29.81) $59.62
Pins (500 for 5.79) $5.79
Styrofoam core poster board, 0.6cm/1/4” thick (3.90 for 25 sheets) $7.80
Razor blade knife (6.29 each) $62.90
Paper (Quiz, .01 x 30, printed on front and back-2 page quiz) $0.30
Estimated total, one-time, start-up cost: $258.82
Time:
Initial Preparation time: 60 – 120 minutes (buying supplies)
Preparation time: 10 -15 minutes (getting supplies together before lesson)
Instruction time: 30 – 60 minutes
Clean-up time: 10 minutes
Assessment (include all assessment materials):
QUIZ – 30 copies printed before lesson
1. Sketch a normal fault.
2. Sketch a reverse fault.
3. Sketch a strike-slip fault.
4. Name the 3 plate tectonic boundaries types discussed in class and provide an example of what happens at these boundaries.
5. True or False: There are only plates below the continents.
Math Time!!! (HOORAY!!!)
Saturn Data:
| |Metric |British |
|Diameter |120,536 km |37,448.80 miles |
|Mass |5.6846×1026 kg |1.2532x1022 pound |
|Rotation on Axis |10h 47m |10 hours 47 minutes |
Note:
Scientific notation: 1x1012 = 1,000,000,000,000 or 1e+12 = 1,000,000,000,000
Formulas:
Surface Area of a Sphere:
SA = 4(r 2
Velocity:
v = (d/(t
Volume:
V = (4/3) (r3
r = ½ Diameter
Circumference = ( Diameter
Abbreviations:
• ( = (pi) 3.14 (circumference/diameter)
• ( = change (( = end - begin)
• D = density
• d = distance
• m = mass
• r = radius (derived from diameter)
• SA = Surface Area
• t = time
• v = velocity
• vol = volume
What is the surface area of Saturn?
◆ r = ½ 120,536km or 60,268km
SA = 4(r 2
4 (3.14 (60268km2))
45620831709.44km2
What is the velocity of Saturn?
◆ To derive distance traveled, we follow one spot on Saturn’s equator as it travels all the way around and back to the beginning. That is the circumference.
• Circumference = 3.14(120,536km) or 378,483.04 (to verify, the actual circumference is 380,887km – but remember that our calculation is for a perfect sphere, and Saturn experiences the greatest oblation, so the actual is larger that the calculated.
• (( = ending – beginning, so (d = 378,483 – 0, and (t = 10 hours 47 min. – 0. then, we need to find the fractional hour in 47 minutes, or 47/60 = 0.7833)
v = (d/(t
378,483km/10.7833hr
35,099.0 km/hour
What is the volume of Saturn?
V = (4/3) (r3
(4/3) (3.14) (60,268km3)
916,491,866,031,820km3
Now, let’s figure out those same questions for Earth, but this time, you do it by yourself!
Earth Data:
| |Metric |
|Diameter |12,750 km |
|Mass |5.9736×1024 |
|Rotation on Axis |23h 56min 4.09s |
Your Calculations Here:
What is the surface area of Earth?
What is the velocity of Earth?
What is the volume of Earth?
|Teaching About Plate Tectonics and Faulting Using Foam ModelsÓ | |
|L.W. Braile, | |
| Professor |[pic] |
| Purdue University | |
|(braile@purdue.edu) | |
| | |
|September, 2000 | [pic] |
Objective: Demonstrate plate tectonic principles, plate boundary interactions and the geometry and relative motions of faulting of geologic layers using 3-D foam models. The foam models aid in visualization and understanding of plate motions and faulting because the models are three-dimensional, concrete rather than abstract descriptions or diagrams, can be manipulated by the instructor and the students, and the models can show the motions of the plates and faults through time in addition to the three-dimensional configuration of the plates or layers. The fault and plate boundary models shown here illustrate relatively simple motions and geologic structures. Although these models are accurate representations of real Earth faulting and plate tectonic structures and motions, the spherical shape of the Earth and the complexity of geological features caused by varying rock types and rock properties and geological development over many millions or hundreds of millions of years, result in significant complexity and variability of actual fault systems and plate tectonic boundaries.
Materials:
• Foam (open cell, foam mattress type) “blocks” shown in Figure 1A
• Felt pens (permanent marker, red and black)
• Manila folders or thin poster board
• Rubber cement
• Closed cell foam (“sleeping bag pads,” camping equipment) as shown in Figures 3 and 5
• Pins
• Open cell foam as shown in Figure 3A
• Styrofoam core poster board, 0.6 cm (1/4 in) thick, as shown in Figure 3B
• Razor blade knife
• Metric ruler
Procedure:
Faulting and Plate Boundaries
1. Prepare foam block models as shown in Figure 1A. The cardboard (cut from manila folders or thin poster board) attached to both faces of the fault plane allows the blocks to slip easily along the fault as forces are applied to the blocks. Use the block models to demonstrate extensional (normal) faulting as the two outer blocks are moved apart as shown in Figure 1B. This procedure is best performed by holding the blocks “in the air” in front of you, supporting the model by the two outer blocks, rather than on a table. Note that as the two outer blocks are moved apart, the inner block drops downward or “subsides.” This relationship between extensional motion of geologic layers and downdropped fault blocks (graben or rift valley if the downdropped block is bounded on both sides by normal faults, as in this block model) produces normal faulting (Figure 2) and also represents the extensional motion and resultant rift development associated with divergent plate boundaries (Table 1). Examples of divergent plate boundaries, where extensional faulting is prominent, are the mid-ocean ridge system in which a narrow rift or graben (downdropped fault block) is commonly observed along the highest part of the ridge (see section 2 below) and the East African Rift in which extension has been occurring in the continental lithosphere for about 30 million years and the resulting rift system of normal faults is beginning to break apart the continent. In a plate-tectonic-related, but not plate boundary environment, the Basin and Range area of the Western United States displays a prominent topographic signature of extensional faulting with many adjacent downdropped fault blocks or grabens (the topographic “high” areas between the grabens are called horsts; see IRIS poster on western US seismicity and topography).
To demonstrate compressional motion and resulting reverse (also called thrust) faults (Figure 2), hold the foam block models as described above and then move the two outer blocks together as in Figure 1C. The inner block will be thrust upwards producing reverse faults and an uplifted block. In a plate tectonic setting, such compressional motion is associated with convergent plate boundaries (Table 1) where two lithospheric plates are moving together or colliding (see also section 3 below). Not surprisingly, these convergent zones are associated with mountain ranges (Himalayas, Alps, Andes, Cascades, etc.).
To demonstrate horizontal slip or strike-slip fault motion, prepare foam blocks as shown in Figure 1D. Moving the blocks horizontally on a tabletop, as shown in Figure 1E, demonstrates strike-slip (Figure 2) or horizontal slip fault motion. This motion along a plate boundary is also called transform (Table 1). The San Andreas fault zone is a system of strike-slip faults which form the transform plate boundary at the western edge of the North American Plate. Transform faults also occur as oceanic fracture zones between segments of the mid-ocean ridge spreading zones (see ocean bathymetry map in a world atlas, such as the National Geographic World Atlas, or view ocean bathymetry on the Internet at: ; click on one of the regions containing a mid-ocean ridge to see details of ridge crest and transform fault topography of the ocean floor).
2. Divergent Plate Boundary and Sea Floor Spreading − Prepare the foam pieces that represent the oceanic lithosphere at a spreading center (mid-ocean ridge divergent plate boundary) as shown in Figure 3A. Cut 10 one cm by 20 cm strips of the closed-cell foam material. Color half of the strips black with the felt pen and label all of the foam pieces as shown in Figure 3A. Construct a “ridge” (optional) to form the base for the sea floor spreading model. The ridge surface represents the top of the asthenosphere in the upper mantle and the foam layer above the base is the oceanic lithosphere - typically about 50-100 km thick in the Earth. The base also provides a mid-ocean ridge topography in which the spreading and extension occurs along the narrow rift zone along the ridge crest.
To demonstrate the concepts of a divergent plate boundary and mid-ocean ridge spreading centers, begin by placing the two 20 x 20 cm foam pieces on the base (Figure 3B) with one edge adjoined at the ridge crest and the arrows on the foam pieces pointing outward (Figure 3A). These squares will represent oceanic lithosphere at a time five million years ago and thus contain oceanic crust (the upper layer of the lithosphere) that is 5 million years old and older. Slide the two foam squares away from each other about 2 cm (this process represents the passage of time and the extension of the lithosphere in the region of the ridge crest, and rift valley, by plate tectonic motions which are typically a few centimeters per year, equivalent to a few tens of km per million years) and place the two strips labeled 4 million years in the space that is created. Attach one strip to each edge of the squares using pins. In the real mid-ocean ridge, a void space or opening between the plates created by the spreading process, would not actually develop. Instead, as extension occurs, volcanic and igneous intrusion processes will relatively continuously fill in the extended lithosphere, in the process creating new lithosphere. Because the oceanic crustal layer in this new lithosphere is formed from igneous (volcanic and intrusive) processes, it cools from a liquid and the rocks acquire a remanent magnetic direction that is consistent with the Earth’s magnetic field direction at that time. Because the Earth’s magnetic field occasionally reverses its polarity (north and south magnetic poles switch), the lithosphere created at mid-ocean ridges displays “stripes” of normal and reversed magnetic polarity crust approximately parallel to the ridge crest. Additional information on these magnetic stripes and mid-ocean ridge processes can be found in “This Dynamic Earth”. The igneous rocks which are formed at the ridge crest can also be “dated” using radiometric dating of rock samples to determine the age of the volcanism and intrusion.
Continue to extend the two plates away from each other at the ridge crest and add the new pieces of lithosphere (attach with pins) which are labeled in decreasing age (3, 2, 1 and 0 million years old). When you are finished, the mid-ocean ridge divergent plate boundary and adjacent lithosphere should look like the diagram shown in Figure 3A and represent a modern (zero million years old) mid-ocean ridge spreading center. Note that the youngest rocks are in the center, along the ridge crest, and the rocks are progressively older (to 4 million years old in the strips and 5 million years old and older in the lithosphere represented by the squares of foam) away from the ridge crest.
3. Convergent Plate Boundary and Subduction − Arrange two tables of identical height to be next to each other and about 30 cm apart as shown in Figure 4. Place the two pieces of one-inch thick foam on the tables and begin to move one piece of foam (the one without the cardboard edge) toward the other and allow it to be “thrust” beneath the other piece of foam. The foam pieces represent two lithospheric plates. As the convergence continues, the underthrust plate will form a subducted slab of lithosphere (extending to at least 600 km into the mantle in the Earth) as shown in Figure 4. Earthquakes commonly occur along the length of the subducted slab and compressional structures (folds and faults) are often associated with the compressional zone near the colliding plates. The subducted lithosphere consists of relatively low-melting-point rocks (sediments and oceanic crust form the upper layers of the oceanic lithosphere) which can melt at depths of 100-150 km as the slab is subducted into the mantle. These molten materials can then ascend through the overlying mantle and crust and form volcanoes which are often situated in a linear chain or arc about 100-200 km away from the collision zone. A deep ocean trench also forms above the point of convergence of the two plates as the oceanic lithosphere is bent downwards by the collision.
4. Transform or Strike-Slip Plate Boundaries and Elastic Rebound − Use a razor-blade knife to make the foam “plate” models shown in Figure 5. The foam is 1.25 cm (1/2”) thick closed-cell foam often used for “sleeping pads” for camping. It is available at camping supply stores and Wal-Mart and Target. The foam pieces can be used on a table top or on an overhead projector (the slits cut in the foam allow the 10 cm long tabs which bend to be seen projected onto a screen). By continuously sliding the two plates past each other with the “tab” edges touching (Figure 5), the foam pieces represent lithospheric plates and the “zone” where the plates touch is a strike-slip (transform) fault. Note that as the plates move slowly with respect to each other (just as Earth’s lithospheric plates move at speeds of centimeters per year), the area of the plates adjacent to the fault (the tabs) becomes progressively bent (deformed), storing elastic energy. As the process continues, some parts of the fault zone will “slip” releasing some of the stored elastic energy. This slip occurs when the stored elastic energy (bending of the tabs) results in a force along the fault which exceeds the frictional strength of the tabs that are in contact. Sometimes, only small segments of the fault zone (one or two tabs) will slip, representing a small earthquake. At other times, a larger segment of the fault will slip, representing a larger earthquake. Note that although the plate motions are slow and continuous, the slip along the fault is rapid (in the Earth, taking place in a fraction of a second to a few seconds) and discontinuous. The motions and processes illustrated by the foam model effectively demonstrates the processes which occur in actual fault zones and the concept of the elastic rebound theory (Bolt, 1993). A brief segment during the beginning of the video “Earthquake Country” illustrates a similar “stick-slip” motion using a model made of rubber strips.
Extensions, Connections, Enrichment:
1. Good preparatory lessons for these activities are studies of elasticity (a spring and masses can be used to demonstrate the two fundamental characteristics of elasticity - the stretching is proportional to the force (suspended mass) and the existence of the “restoring force” (elastic energy is stored) in that the spring returns to its original length as the force (mass) is removed), and seismic waves which are generated as the fault slips.
2. The stick-slip process is well illustrated in a segment of the NOVA video “Killer Quake” in which USGS geophysicist Dr. Ross Stein demonstrates this process using a brick which is pulled over a rough surface (sandpaper) using an elastic cord (bungy cord). An experiment using this same procedure is described in “Seismic Sleuths” (AGU/FEMA).
3. Additional information on plate tectonics is available in Bolt (1993), Ernst (1991), Simkin et al. (1994), the TASA CD “Plate Tectonics,” “This Dynamic Earth,” and nearly any secondary school or college level geology textbook. Elastic rebound is well illustrated in Lutgens and Tarbuck (1996), Bolt (1993) and the TASA CD. A color map of the Earth’s plates is available on the Internet at: . An excellent description of plate tectonics can be found at: .
4. An additional plate tectonic activity is the EPIcenter lesson plan “Voyage Through Time - A Plate Tectonics Flip Book” in which continental drift during the past 190 million years - a consequence of plate tectonics - is effectively illustrated; and Plate Puzzle which uses the "This Dynamic Planet" map.
5. Additional plate tectonic activities, especially for younger students, are contained in “Tremor Troop” (NSTA/FEMA).
6. A leading theory explaining why the Earth’s plates move is convection currents in the Earth’s mantle. The interior structure of the Earth is described in Bolt (1993) and is the subject of the EPIcenter activity “Earth’s Interior Structure.” Good activities illustrating convection are contained in the GEMs guide “Convection - A Current Event” (Gould, 1988), or “Tremor Troop” (NSTA/FEMA).
References:
Bolt, B.A., Earthquakes and Geological Discovery, Scientific American Library, W.H. Freeman, New York, 229 pp., 1993.
Braile, L.W., “Earth’s Interior Structure” - .
Braile, L.W. and S.J. Braile, “Voyage Through Time - A Plate Tectonics Flip Book” - .
Braile, L.W. and S.J. Braile, "Plate Puzzle" – .
Ernst, W.G., The Dynamic Planet, Columbia University Press, New York, 281 pp., 1990.
FEMA/AGU, Seismic Sleuths - Earthquakes - A Teachers Package on Earthquakes for Grades 7-12, American Geophysical Union, Washington, D.C., 367 pp., 1994. (FEMA 253, for free copy, write on school letterhead to: FEMA, PO Box 70274, Washington, DC 20024).
Gould, A., Convection - A Current Event, GEMS, Lawrence Hall of Science, Berkeley, California, 47 pp., 1998.
IRIS, Western US Seismicity and Topography Poster, iris.edu.
Lutgens, F.K., and E.J. Tarbuck, Foundations of Earth Science, Prentice-Hall, Upper Saddle River, New Jersey, 482 pp., 1996.
NSTA/FEMA, Tremor Troop - Earthquakes: A teacher’s package for K-6 grades, NSTA Publications, Washington, DC, 169 pp., 1990. (This book contains a reasonably complete curriculum for teaching earthquake and related Earth science topics; FEMA 159, for free copy, write on school letterhead to: FEMA, PO Box 70274, Wash., DC 20024).
Simkin et al., This Dynamic Planet, map, USGS, 1:30,000,000 scale ($7 + $5 shipping), 1994, also at: ; 1-888-ASK-USGS.
TASA “Plate Tectonics” CD-Rom - Plate tectonics, earthquakes, faults, ($59 or $155 for site license), (800-293-2725) , Mac or Windows.
U.S. Geological Survey, This Dynamic Earth: The Story of Plate Tectonics, available from: U.S. Geological Survey, Map Distribution, Federal Center, PO Box 25286, Denver, CO 80225, $6, (800 USA MAPS). Also available (full text and figures) for viewing at: .
Videos (NOVA “Killer Quake,” and “Earthquake Country”) - information available in “Seismology-Resources for Teachers” online at: .
[pic]
Figure 1. Foam (soft, open cell foam used for mattresses) blocks for demonstrating faults (normal, reverse and strike-slip) and motions at plate boundaries (divergent and extensional motion; convergent and compressional motion; transform and horizontal slip motion). Large arrows show direction of force or plate motion. Half-arrows along faults show direction of relative motion along the fault plane. Shaded area is red felt pen reference line. A. Foam block with 45° angle cuts (cardboard, cut from manila folders, attached to angled faces with rubber cement) and reference line drawn on the side of the blocks with a felt pen. B. Response of model to extension. C. Response of model to compression. D. Foam blocks used to demonstrate strike-slip motion. Cardboard is attached to the two faces (as shown in Figure) using rubber cement. Reference lines and arrows are drawn on the top of the foam blocks using a felt pen. E. Response of model to horizontal slip motion.
[pic]
Figure 2. Block diagrams illustrating types of geological faults with resulting offsets of layers. Half-arrows show relative motion of the blocks along the fault plane.
[pic]
Figure 3. Foam pieces for demonstrating divergent plate boundaries and a mid-ocean ridge spreading center. Cut out pieces with razor blade knife and straight-edge. A. Top view of foam blocks after assembly (see text) representing 5 million years of extension at the ridge crest and generation of new lithosphere by magmatic (igneous) processes. Numbers are ages in millions of years. In the real Earth, the time periods of normal (shaded) and reversed polarity would not be of equal duration (one million years in this simulation) and thus the ‘stripes” would be of varying widths. B. Side view showing foam pieces on top of styrofoam base (two pieces, each 20 cm x 30 cm) which creates slopes representing the mid-ocean ridge. Attach styrofoam with pins to foam piece (2 cm x 20 cm) used to create slope.
[pic]
Figure 4. Foam (soft, open cell foam) pieces (each piece is 50 cm by 15 cm by 2.5 cm (1 in) thick) used to demonstrate convergent plate motions and subduction. Edge of one of the foam pieces is cut at a 45 angle and lined with cardboard (manila folder material), using rubber cement to attach the cardboard to the foam.
[pic]
Figure 5. Foam pieces used to demonstrate strike-slip faulting, elastic rebound theory, and slipping along the fault plane during earthquakes. Cut out slits with razor blade knife and straight-edge.
Table 1. Faults, Plate Boundaries and Relative Motions*
|Relative Motion of | | | |
|Layers or Plates |Fault Names |Plate Boundary |Related Tectonic and Geologic Features |
| | |Descriptions | |
|Extension |Normal |Divergent (extensional, moving apart, spreading, |Rifts, grabens, sometimes volcanism, regional |
| | |construction - because new lithosphere is |uplift but local downdropped fault blocks, |
| | |generated in the extended zone) |shallow earthquakes |
|Compression |Reverse or Thrust |Convergent (compressional, collision, subduction, |Folded mountain ranges, uplift, reverse faults,|
| | |moving together, destructive - because one plate |volcanic arcs (usually andesitic composite |
| | |is often thrust into the mantle beneath the other |volcanoes), deep ocean trenches, shallow and |
| | |plate) |deep earthquakes in subducted slab |
|Translation or |Strike-slip |Transform (horizontal slip, translation) |Linear topographic features, offset stream |
|horizontal slip | | |channels, lakes in eroded fault zone, |
| | | |pull-apart basins and local uplifts along fault|
| | | |bends or “steps” between offset fault segments,|
| | | |oceanic fracture zones, offsets of mid-ocean |
| | | |ridges |
*Many terms and geological “jargon” are associated with faults and plate boundaries. While these terms are useful to Earth scientists and are included here and in the accompanying text for completeness, the most important concepts such as extension, moving apart, downdropped blocks, etc., can be discussed and understood without unnecessary jargon. Additional information on the terms and concepts used here can be found in virtually any introductory geology textbook or in the USGS booklet “This Dynamic Earth - The Story of Plate Tectonics.”
ÓCopyright 2000. L. Braile. Permission granted for reproduction for non-commercial uses.
ADDITIONAL LESSON PLAN IDEA, COURTESY OF AN ONLINE SEARCH FOR CONTINENTAL PLATES LESSON PLANS:
Snack Tectonics
Students use graham crackers and frosting to learn about the different aspects of plate tectonics. They manipulate the graham crackers in various ways to model divergent plate boundaries, convergent plate boundaries - continental and oceanic, convergent plate boundaries - continental, and lateral plate boundaries. Students observe what happens to the graham crackers and frosting and discuss their findings.
Below is a description of the activity from
|A crack in the earth's crust is called a fault. The large crack where two |What you'll need: |
|huge earth plates move against each other is a fault line. Fault lines are |[pic] |
|where the action happens. |Graham crackers |
| | |
| |[pic] |
| |Waxed paper spread with a thick layer of frosting or peanut butter. |
| | |
| |[pic] |
| |Milk (To drink with the crackers after finishing the experiments.) |
| | |
|Put two graham crackers side by side, and slide one up away from you and the |Whose fault is this? |
|other one down toward you. |What if you went outside after an earthquake and found the raspberries |
|When plates move past each other like this, things don't exactly go smoothly. |your family planted in the front yard were growing in front of your next |
|In fact, the plates usually get stuck on each other and then give a lurch and |door neighbor's house ( and in your yard were the roses from the next |
|move on, sending waves of vibrations through the earth's interior (much like |house)? This is what happened in San Francisco along one of the most famous|
|the circular waves that ripple out when you drop a pebble in the water). These|fault lines in the world— the San Andreas Fault in California, a 600 -mile |
|vibrations are so powerful the we have a special name for them— earthquake! |boundary where the American and Pacific Plates meet. In 1906, there was an |
| |earthquake along this fault line and the earth moved about 20 feet in less |
| |than a minute! Wonder who got to eat the ripe berries? |
|These two delicious and fun projects and many more can be found in GEOLOGY |Put two graham crackers very close to each other on the wax paper and |
|ROCKS!, a Williamson Publishing book by Cindy Blombaum |slowly push them together. |
| |You've made a rift, or big crack in the ocean floor. As the plates |
| |separate, magma oozes up from below and makes new ocean floor or creates |
| |underwater mountain ranges. |
| | |
|Push two crackers toward each other, make one slide underneath the other. |Put two graham crackers side by side on the wax paper (wet the edge of one |
|When this happens on earth, watch out! The bottom plate starts to melt from |graham cracker in milk first), and slowly push them together. |
|the intense heat and pressure. It becomes new magma that floats up between two|The ridge of pushed -up cracker is just like many mountain ranges around |
|plates, building up and up over many years until it finally causes a volcano |the earth that were formed as two plates slowly crumbled together over |
|blast! That plate action caused Mt. St. Helens in Washington State to blow its|millions of years. The Himalayas ( the mountain range that includes Mount |
|top! |Everest) were formed when India crashed into Asia. |
| | |
[pic]
A similar, but more complete, lesson is given in Windows to the Universe. The materials needed are:
For each student:
|[pi|One large graham crackers broken in half (i.e., two square graham crackers) |
|c] | |
|[pi|Two 3-inch squares (approx.) of fruit roll up |
|c] | |
|[pi|Cup of water |
|c] | |
|[pi|Frosting |
|c] | |
|[pi|About one square foot of wax paper with a large dollop of frosting. ( Instruct students to spread frosting into a layer about half a cm thick.) |
|c] | |
|[pi|Plastic knife or spoon |
|c] | |
Activity:
Directions overheads:
ADDITIONAL LESSON PLAN IDEA, COURTESY OF AN ONLINE SEARCH FOR CONTINENTAL PLATES LESSON PLANS:
“Egg Plates”
The following are my additional ideas but they are not laid out in the traditional lesson plan format because I did not have time for that much detail before submitting my lesson plan!
1. Have a game at the end of the unit for the kids to show all of the wonderful knowledge they have learned. I would use many questions from the following website:
And incorporate my own questions based on what was presented.
The game could be played like Jeopardy, with the students in groups who work together on answering the questions.
2. Assign each student/pair of students a specific plate. They can do many things with this:
a. Create a poster
i. Geography
ii. Geology
iii. Climate
iv. Biomes
v. Direction the plates are moving
vi. Plates it will eventually collide with
vii. Fun facts
viii. Etc.
b. Create a report with the same information
c. Create a simple oral presentation
d. Create an in depth presentation
3. Do a lesson where they dive deep into the mathematics of the plates. Give them the direction the plates are moving and the speeds/velocity. They can work through a set of math problems to calculate when certain plates will collide or certain oceans will open up, etc.!
4. Use Google Earth to locate some of the boundaries and look at the ocean bottoms!
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