Plate Tectonics Question Bank



Earthquakes and Volcanoes Practice Questions

When necessary, USE YOUR ESRT Packet pages provided to you to assist in answering these questions.

1. An earthquake’s P-wave arrived at a seismograph station at 02 hours 40 minutes 00 seconds. The earthquake’s S-wave arrived at the same station 2 minutes later. What is the approximate distance from the seismograph station to the epicenter of the earthquake?

1100km

Base your answers to questions 2 through 4 on the map below, which shows the location of the Peru- Chile Trench.

2. The Peru-Chile Trench marks the boundary between which two plates?

Nazca and South American Plate

3. In which diagram do the arrows best represent the motions of Earth’s crust at the Peru-Chile Trench?

[pic]

4. What observations of geologic formations in this region (on the map) could provide the best evidence of the pattern of crustal movement at the Peru- Chile Trench?

The parallel arrangement of the oceanic trench and the continental volcanic arc (Andes)

5. Using the Travel-Time Graph provided, approximately how long does an earthquake P-wave take to travel the first 6500 kilometers after the earthquake occurs? 10 mins.

Using Inferred Properties of Earth’s Interior supplement:

6. Compared to Earth’s crust, describe the density, relative temperature and composition of the core.

Density of core is 4x greater than crust, its temp is 6500 degrees Celsius hotter, and it is composed of iron and nickel.

7. What are the difference between P waves & S waves in how they travel, what they can/can’t travel through and speed of travel.

Pwaves=Phastest waves, they are compressional waves (travel parallel) travel through solid rock and liquid core.

Swaves=travel half as fast as Pwaves, transverse (up and down, perpendicular) waves, travel only through solid rock and therefore cannot be felt on other side of the earth.

Base your answers to questions 8 through 10 on the map and data table below. The map shows the locations of volcanic islands and seamounts that erupted on the seafloor of the Pacific Plate as it moved northwest over a stationary mantle hotspot beneath the lithosphere. The hotspot is currently under Kilauea. Island size is not drawn to scale. Locations X, Y, and Z are on Earth’s surface.

8. Approximately how far has location X moved from its original location over the hotspot?

1700km

9. According to the data table, what is the approximate speed at which the island of Kauai has been moving away from the mantle hotspot, in kilometers per million years?

545km/5,600,000years = .000097km/year

10. Which lithospheric plate boundary features are located at Y and Z?

Subduction zones, trenches, volcanoes

11. The Himalayan Mountains are located along a portion of the southern boundary of the Eurasian Plate. At the top of Mt. Everest (29,028 feet) in the Himalayan Mountains, climbers have found fossilized marine shells in the surface bedrock. From this observation, what is the best inference about the origin of the Himalayan Mountains? The crust of the Indian and Eurasian plates was originally below sea level (millions of years ago). As those plates collided (converged), the crust was thrust upward to where they are today where the fossil evidence is found.

Using Inferred Properties of Earth’s Interior supplement:

12. Describe the state of matter and the average density of the Earth’s outer core. It is melted iron and nickel with a density range of 9.9-12.2g/cm3

Base your answers to questions 13 through 15 on the map below. The map shows the locations of deep-sea core drilling sites numbered 1 through 4. The approximate location of the East Pacific Ridge is shown by a dashed line. Point A is located on the East Pacific Ridge.

13. At point A, the East Pacific Ridge is the boundary between which two plates? Nazca and Pacific

14. At which drilling site would the oldest igneous bedrock most likely be found? Explain.

Site 1 because new rock formed at ridge continues to push outward at the divergence causing older crust to occur at points farther from the ridge.

15. Compare the thickness and density of the continental crust of South America to the oceanic crust of the Pacific floor. Oceanic crust is much thinner and far denser than oceanic crust. Where the Nazca plate subducts under the South American plate, the Andes Mountains formed, which is very thick crust.

Base your answers to questions 16 and 17 on the map below. Seismic stations are located at the four cities shown on the map. Letter X represents the epicenter of an earthquake determined from seismic waves recorded at all four cities. You may need to use the Travel-time graph.

16. At which city is there a difference of approximately 3 minutes and 20 seconds between the arrival times of the P-waves and the S-waves?

Find 3:20 difference on Travel Time graph, which is 2000km, then measure distances of each city to epicenter using scale. NEW ORLEANS

17. Which map below correctly shows how the location of the epicenter was determined?

18. Which direction is this plate moving? WNW

19. Describe the formation of the Hawaiian Islands. The Pacific plate moving over the hot spot over millions of years. As it sits directly over the hotspot, the crust bulges upward as it is heated and magma seeps to the surface where it hardens and cools. This eventually creates an island. All of the Hawaiian Islands are formed this way. The hotspot is currently under the big island of Hawaii, but was previously under the island of Maui.

20. Describe the formation of seamounts.

Millions of years ago, the hotspot was under the seamounts that USED to be islands. As the plate moved past the hot spot, the land slumps slightly because no longer uplifted by the heat of the hot spot. Over the course of millions of years, these landforms that used to be islands, become eroded by wind and water and eventually become submerged into the seamounts they are today.

Base your answers to questions 21 and 22 on the diagram below, which shows a portion of Earth’s interior. Point A is a location on the interface between layers.

[pic]

21. The arrows shown in the asthenosphere represent the inferred slow circulation of the plastic mantle by a process called Convection.

22. Use Inferred Properties of Earth’s Interior: The temperature of rock at location A is approximately ___2600______________°C.

The diagram below shows the bedrock structure beneath a series of hills.

23. Which type of fault was primarily responsible for forming the hills?

Normal fault (hanging wall sinks)

24. What type of force causes this fault?

Tension (pulling)

The map below shows the Atlantic Ocean divided into zones A, B, C, and D. The Mid-Atlantic Ridge is located between zones B and C.

[pic]

25. Using the information provided and what you know about the age of rocks at mid-ocean ridges, draw a graph of the geologic age of the surface bedrock on the ocean bottom.

The diagram below shows land features that have been disrupted by an earthquake.

26. Which type of crustal movement most likely caused the displacement of features in this area?

Shearing at a strike-slip fault.

The diagram below is a seismogram of the famous San Francisco earthquake of 1906, recorded at a seismic station located 6,400 kilometers from San Francisco.

[pic]

27. If every ¼ inch is 1 minute, what is the time difference between the arrival of the P and S waves? 7mins

28. Using your travel time graph, how far was this station from the earthquake epicenter? 5250km

Base your answers to questions 29 and 30in part on the news article and map below. Points A and B on the map are reference points.

Huge Quake Possible in Oregon Valley

Scientists have warned for years that a magnitude 8 or 9 earthquake could strike about 30 miles off the Oregon coast, causing huge tsunamis (large ocean waves) and tremendous damage.

Now scientists say these earthquakes could be centered much farther inland and cause severe damage to a larger area, including cities in Oregon such as Portland, Salem, and Eugene.

Geologic evidence suggests that strong quakes in this area occur about every 400 years, plus or minus 200 years. The last one, believed to be a magnitude 9, occurred 300 years ago.

A magnitude 8 quake can cause tremendous damage. The San Francisco quake of 1906 has been estimated at 7.9. The Mexico City quake of 1985 that left thousands dead was measured at 8.1.

29. The cross section below shows the lithosphere and asthenosphere between points A and B on the map.

a On the cross section below, draw an arrow in the Juan de Fuca Plate to indicate the direction of the relative movement of the plate.

b Identify the type of tectonic plate boundary that exists at the Juan de Fuca Ridge. Divergent

c Identify the name of the plate in the cross section labeled x. Pacific Plate

d How does the average earthquake depth beneath the Oregon coastline compare to the average earthquake depth beneath Mt. Hood?

More shallow at coastline because the plate is just starting to subduct, whereas at Mt. Hood, the earthquakes would happen deeper as Juan de Fuca is subducted deeper.

30. An emergency management specialist in Portland, Oregon, is developing a plan that would help save lives or prevent property damage in the event of a future earthquake. Describe two actions or ideas that should be included in the plan. You may need to use 8.3 in your text book for this.

(1) ___use your book to find these answers__________________________________________________________

_________________________________________________________________

(2) _____________________________________________________________

_________________________________________________________________

Base your answers to questions 31 through 34 on the diagram and map below. The diagram shows three seismograms of the same earthquake recorded at three different seismic stations, X, Y, and Z. The distances from each seismic station to the earthquake epicenter have been drawn on the map. A coordinate system has been placed on the map to describe locations. The map scale has not been included. You many need to use the travel-time graph provided to you.

[pic]

[pic]

31. Approximately how far away from station Y is the epicenter? 4 min=2600km

32. What will happen to the S-waves from this earthquake that travel toward Earth’s center? Why does this happen?

Get deflected off of the core because they cannot travel through “liquid”.

33. Seismic station Z is 1,700 kilometers from the epicenter. Approximately how long did it take the P-wave to travel to station Z? 3min 30 sec.

34. On the map, which location is closest to the epicenter of the earthquake? Station X (because shortest lag time between arrival of P and S waves)

Base your answers to questions 35 and 36 on the earthquake seismogram below. Use Travel Time graph if necessary.

[pic]

35. When did the first P-waves arrive at this seismic station? How far away from the epicenter is this earthquake?

11:01am; 2600km

36. How many additional seismic stations must report seismogram information in order to locate the epicenter of this earthquake?

2 more for a total of 3 in order to triangulate to find the epicenter.

Base your answers to questions 37 through 39 on the data table below, which gives information collected at seismic stations A, B, C, and D for the same earthquake. Some of the data has been deliberately omitted. Use Travel Time Graph where necessary.

[pic]

37. What is the most probable reason for the absence of S-waves at station A? A must be on the opposite side of the earth because S waves cant travel through the core.

38. What is the approximate distance from station C to the earthquake epicenter? 1600km

39. How long did it take the S wave to travel from the epicenter of the earthquake to seismic station D? 17:20

Read about the Hazards caused by earthquakes in 8.3 of your textbook. Base your answers to questions 40 through 42 on the passage and map below and your knowledge of EQ hazards. The passage provides some information about the sediments under Portland, Oregon, and the map shows where Portland is located.

Bad seismic combination under Portland: Earthquake faults and jiggly sediment

Using a technique called seismic profiling, researchers have found evidence of ancient earthquake faults under Portland, Oregon. The faults may still be active, a USGS [United States Geological Survey] seismologist will announce tomorrow.

The research also turned up a 250-foot deep layer of silt and mud, deep under the city, which may have been caused by a catastrophic ice dam break some 15,000 years ago.

The two findings could together mean bad news, as soft sediment is known to amplify ground shaking during strong earthquakes. In the 1989 San Francisco earthquake, much of the damage to buildings was caused by liquefaction, a shaking and sinking of sandy, water saturated soil along waterways. . . .

— Robert Roy Britt

excerpted from

“Bad sesimic combination under Portland:

Earthquake faults and jiggly sediment”

05/03/99

40. Explain why Portland is likely to experience a major earthquake.

Portland sits above the subduction zone where the Juan de Fuca plunges under the North American Plate. Rock grinds against rock, eventually breaks, releases energy in the form of an earthquake.

31. Why is the presence of a layer of silt and mud deep under the city a danger to Portland?

Liquefaction can occur, causing buildings to sink into the ground.

42. What type of tectonic plate boundary is shown at the San Andreas Fault? Transform plate boundary

Volcanoes: Use your textbook to answer these questions

1. What is the relationship between a magma’s viscosity and its silica content?

2. How does temperature affect viscosity of magma? Gas content?

3. What factors affect the “violence” of a volcanic eruption?

4. What is pyroclastic flow? List and describe the different types and what causes each.

5. Distinguish between the three types of volcanoes in shape and how they form.

6. Label the parts of the diagram above.

7. What type of volcano is figure 10-1 showing?

8. What is a caldera and how does it form?

9. What is a lava plateau?

10. How is magma formed? Why does it rise to the surface?

11. What is the Ring of Fire? Where is it located?

12. What type(S) of plate boundaries form volcanoes?

13. What is a hot spot? Give an example of a volcano formed by one.

14. In what ways are volcanoes that form at ocean-continent convergent boundaries different from those that form at divergent boundaries? (Aside from one being continental volcanic arc and the other being island volcanic arc.)

15. Compare and contrast rhyolitic magma to basaltic magma in terms of silica content, viscosity, gas content, formation of pyroclastics, landforms produced.

16. How can explosive volcanic eruptions affect the temperature and weather around the world?

17. Would you be safer from a violent, explosive eruption while vacationing in Arizona near a cinder cone or while skiing in the Andes Mountains of South America? Explain.

18. What is a lahar? Explain why a lahar can occur on a volcano without an eruption.

19. Why is a volcano fed by a highly viscous magma likely to be a greater threat to people than a volcano fed by very fluid magma?

20. Draw a diagram showing the formation of continental volcanic arcs. Give an example of this type of volcanic mountain chain.

21. Draw a diagram showing the formation of island volcanic arcs. Give an example of this type of volcanic mountain chain.

22. Describe how volcanoes can form at intraplate locations. Give an example of such a volcanic formation.

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The block diagram below shows the bedrock age as measured by radioactive dating and the present location of part of the Hawaiian Island chain. These volcanic islands may have formed as the Pacific Plate moved over a mantle hot spot

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