Vocabulary - GSHS Mrs. Francomb



Segment 1: Major Challenge

1. Why is so difficult for scientists to find clues on the birth of the Earth?

Erosion, volcanic activity, shifting plates

2. What did investigators find at Meteor Crater in Arizona?

Meteorites are older than any rocks on Earth

More than four and half billion years ago our Sun came into existence. It is surrounded by a swirling mass of dust.

3. Describe theory of formation of solar system from this dust.

4.5 billion years ago our young sun surrounded by a cloud of gas and dust, as it

cooled grains and minerals formed that bumped into each other to form planets

4. What was the problem with the theory?

Lack of evidence to explain how materials would clump together

Evidence

In 2003, aboard the Space Station a researcher was observing what happens to various materials in the zero gravity of space.

5. What did he observe regarding salt grains?

Salt grains in plastic bag particles immediately began to stick to each other through electrostatic charges.

6. What did scientists then conclude regarding other mineral grains?

If salt sticks together in space then so could mineral grains in the dust cloud

around the sun.

Evidence

7. Stony Meteorites – What do planetary scientists find in them?

Pieces of everything that was in the dust cloud

8. Gradual growth of these rocky aggregates, at .5 mile across what critical event happens?

The planet accumulates enough mass that gravity takes control and pulls in surrounding rocks even faster.

Our Earth becomes one of the largest rocks so for 30 million years there is a continuous bombardment resulting in a random accretion. However, geologists know Modern Earth is not like that. Something must have happened.

9. Draw and describe the layers of the Earth

Crust – thin rocky

Mantle – rock layer, hot but not melted

Core – Iron & Nickel

Layers of Earth are a clue to Earth’s formation

10. What extraordinary event occurred to transform the interior?

Complete meltdown

11. How were core and layers formed?

Denser elements sank to core

12. What force was responsible for the creating the core and the layers?

Gravity

13. What caused the heat up?

Incorporation of very hot radioactive elements

14. Describe the Earth, 30 million years after it began to form.

Earth was totally molten, magma oceans were 2000 degrees C and at the edge of the planet space is -450 degrees C

15. With the vast temperature difference what happens?

Surface cannot stay molten long and Earth cools from the outside in. In less than 1

million years a thin crust is formed.

16. However, volcanoes spew __lava_____________ and ___gases____________.

Meteorites rain down in constant bombardment.

** Evidence in Review**

1. Salt grains provide evidence that mineral particles in the dust cloud clumped

together to form the Earth

2. Layers of the Earth provide evidence that the Earth completely melted shortly after it formed.

17. What vital piece of information did scientists still not know?

Age of Earth

Segment 2: Age of the Earth

18. In ___1650______, Irish Archbishop adds up all the ages of prophets and kings in the Bible and concludes the Earth was born at nightfall before Sunday October 23, __4004____ BC. A century later geologists find that sediments and volcanic lavas were laid down over millions of years not thousands. In ___1897_____, physicist Ernest Rutherford figures out how to use radioactive decay to determine age of rock. Some samples are found to be billions of years old.

19. What’s the next major obstacle?

It’s hard to find rocks from these early days due to erosion, continental drift, and tectonic activity

20. What new type of investigation does C.C. Patterson take?

Dating meteorites

21. Explain the logic behind dating meteorites to determine the age of the Earth.

Since meteorites were formed at same time as Earth they must be the same age. At Meteor Crater meteors are found that date to 4.5 billion years old meaning Earth must also be that old

22. Since then modern techniques have refined the age of the Earth to ___4.6 _billion years.

Scientists now knew how and when the Earth was formed.

What happened next?

23. Hardman was researching the origin of the Moon. Summarize the radical new theory proposed by Bill Hardman in 1974.

Intense impacts blew crust/mantle rock off of Earth, planet size of Mars crashed into Earth forming Earth and moon

Evidence

Video footage of astronaut collecting moon rocks in 1972.

24. Why still under lab conditions?

Don’t want humans leaving organic material on it

Originally Moon’s formation was thought to be like Earth’s formation from accretion with layers and an iron core.

25. What happened when the rocks from the 1972 Moon footage were examined and analyzed?

Moon rocks had less iron than expected.

26. How did Hartman interpret this data?

Indicated that the conventional theory about Moon’s formation was wrong- moon made out of material from Earth’s crust and upper mantle

** Evidence in Review**

3. Radiometric dating provides evidence that the earth is about 4.6 billion years old

4. Lack of iron in moon rocks provides evidence that it was not formed at the same time as the Earth. Earth survived a Giant Impact.

Segment 3: Earth still missing 2 essential components

1. Solid land

2. Water

Earth forms from dust cloud surrounding Sun and then survives huge collision with another planet about size of Mars. Jump forward about 200 million years.

27. Northeast shore of Hudson Bay Canada, what caught ONeill’s eye?

The rocks looked different from the other rocks. They were highly altered,

deformed volcanic lavas called amphibolites.

Chemistry and mineralogy were unusual

28. What were the results of the radiometric dating?

Results = Amphibolites formed 4.3 billion years ago

Unbelievable! Redid the test 3 times did with additional samples

29. Why are these results so unbelievable?

These are the oldest rocks found on Earth, this is the closest we’ve come to

finding Earth’s original crust.

30. What clues/evidence do the amphibolites provide about the thickness of the crust 4 billion years ago?

The amphibolites were created at least 12 miles underground, crust that thick

says there must have been continents 4.3 billion years ago.

This rock sequence was formed deep underwater based on its chemical signature.

31. Additional evidence comes from same sequence, what do geologists find?

Banded iron formation

32. What is banded iron formation?

Alternating bands of light silica and dark bands called magnetite

33. Why is this considered to be evidence of water’s presence of Earth more than 4 billion years ago?

Magnetite in banded iron formations only form underwater. Therefore, oceans

also existed 4.3 billion years ago.

** Evidence in Review**

Early Earth 4.3 billion years ago had oceans and continents based on

5. Amphibolites tell us Earth had a thick crust meaning continents existed.

6. Banded iron formations show oceans existed at same time

Segment 4: Where did all the water come from?

34. Why do scientists believe the answer lies in space?

New evidence from a meteorite that fell in 1998 but only recently has been analyzed.

35. What did scientists find in the meteorite?

Grains of table salt. Trapped inside salt crystals were small droplets of liquid water.

36. How old is the salt and therefore the water?

Salt dated 4.5 billion years, so water has to be at least that old, since it’s inside the

salt. Therefore, water is as old as the solar system.

37. Describe how scientists believe all the water we have on Earth arrived here.

Meteorites brought water to Earth, over the course of billions of years of

bombardment droplet by droplet.

Segment 5: Last Phase

With water and continents present stage is set for last phase of Earth’s development

38. Without life what would not exist in terms of geologic features?

Sedimentary rock formations like chalk and limestone

Coal, oil or natural gas

New explanation

39. In the desert of northern Mexico (Allende) what happened that turned night into day?

Large meteorite/fireball- size of car traveling at 36,000 mph entered Earth’s

atmosphere and broke into thousands of pieces, showering of stones over a 5 mile

area.

40. What did samples reveal?

Tiny amounts of amino acids, chemical building blocks of life.

41. What had the scientific world believed about the formation of amino acids before the discovery of the Allende meteorite?

Chemical reactions in warm pools or through lightening causing chemical reactions in the atmosphere.

** Evidence in Review**

Meteorites

7. Water arrived here in meteorites

8. Meteorites also brought amino acids

Segment 6: one more piece. 3.5 billion years ago new forms of life are about to emerge.

42. What element is not present but required for life as we know it?

Oxygen

43. What gases made up the atmosphere at that time?

sulfur, methane, sulfuric acid, carbon dioxide

44. What are stromatolites?

Fossilized remains of corral-like creatures found in rocks all over the world. They provide clue as to how atmosphere changed.

45. Where can living stromatolites be found?

In the northern Mexican desert-- Cuatro Cienegas

3.5 billion years ago Earth was dominated by microbes: Cyanobacteria

Stromatolites are made up of millions of Cyanobacteria

46. What ‘s so special about the Cyanobacteria?

Cyanobacteria produce oxygen (bubble under water). They use sunlight and

water and release Oxygen

Over time trillion of tons of oxygen changes way all life evolves.

47. What are some of the impacts that life has had on geology?

Decaying plant matter built up compressed layers that form all coal, oil and

natural gas

Sedimentary rocks form from skeletons of marine organisms (limestone & chalk)

Evidence

1. Salt grains provide evidence that mineral grains in the solar dust cloud

clumped together to form planets

2. Meteorites provide evidence that Earth formed 4.5 bya

3. Oldest rocks provide evidence that continents and oceans formed 4.3

bya

4. Liquid water in meteorites provide evidence that water was brought drop

by drop during billions of years of meteor showers

5. 3 billion years ago Earth had continents, oceans, oxygen and primitive

life forms.

|Event |Evidence |

|1. The Earth formed by dust and minerals sticking together in |Salt sticks together in space, so minerals and dust must too. |

|the nebula | |

|2. The Earth completely melted from radioactive elements |The Earth has internal layers: core, mantle, and crust |

|3. The Earth and the whole solar system formed about 4.6 billion|Radiometric dating of meteorites |

|years ago | |

|4. The Earth survived a giant impact |Moon rocks are low in iron, so must be formed from Earth’s crust |

| |material that got knocked off |

|5. A thick crust and continents formed 4.3 billion years ago |Amphibolite rocks only form 12 miles deep and they are 4.3 |

| |billion years old. |

|6. Oceans formed 4.3 billion years ago |Banded Iron formations only form under water and they are 4.3 |

| |billion years old |

|7. Water came from space in meteorites, drop by drop |Salt in meteorites contains water droplets, and the salt is 4.5 |

| |billion years old |

|8. Amino acids, a building block of life, came from space |Amino acids were found in meteorites 4.5 billion yearsrs old |

|9. The Earth’s atmosphere changed from toxic to oxygen, allowing|3.5 billion year old stromatolite fossils show that cyanobacteria|

|advanced life to develop. |began to create oxygen gas. |

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