7th - Plate Tectonics & Seafloor Spreading

Before there was evidence from rocks and fossils, many scientists theorized that the continents were once joined together. Using only maps, these scientists observed that--

• weathering and erosion have reshaped the surface of the Earth

• the continents were all bordered by mountain ranges.

• the shapes of the continents allowed them to fit together.

• the oceans have become smaller throughout Earth's history.

Fossils of organisms that once lived in warmer climates millions of years ago have been found in arctic environments today. What fact does this evidence support?

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Answer explanation

Earth's tectonic plates have moved great distances.

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NGSS.MS-ESS2-3

NGSS.MS-LS4-1

The Mesosaurus was a freshwater reptile that existed about 250 million years ago. Why are the fossils of Mesosaurus found today in some rock layers in both South America and Africa?

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Answer explanation

Fossils of Mesosaurus are found in both South America & Africa because the continents were once connected as a single landmass millions of years ago and have moved great distances to their current location today.

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NGSS.MS-ESS2-3

NGSS.MS-LS4-1

Why do the plates shift and move?

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Answer explanation

The plates are floating slowly on Earth's soft, underlying asthenosphere.

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NGSS.MS-ESS2-3

What are some notable landmarks and events associated with plate boundaries?

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Answer explanation

Volcanic eruptions, mountain chains, earthquakes, blocks of sinking crustal material, oceanic trenches, & the formation of new crustal rock along spreading ridges

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NGSS.MS-ESS2-3

NGSS.MS-ESS3-2

How are fossils used by scientists to show that the theory of continental drift is correct?

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Answer explanation

They show us how the continents were connected together, by demonstrating how fossils on one continent were present on other continents at the same time, even though the animals could not have crossed an ocean if there was one in the way. This means that they must have been able to walk from one continent to another because the continents all made one giant landmass.

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NGSS.MS-ESS2-3

Which of the following provides evidence for past tectonic plate motions?

• Matching rock type and rock formation can show the way the continents were once attached.

• Glacial evidence has been found in areas where glaciers could not exist if the continents were in their current location.

• Ancient life forms preserved as fossils can tell us what organisms existed and where they were. Matching the fossils can show that land masses were once connected.

• All of the above.

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NGSS.MS-ESS2-3

NGSS.MS-LS4-1

The distribution of fossils is used as evidence for plate tectonics. The distribution of four different fossil organisms over three different continents is shown in the diagram. The distribution of which organisms can be used as evidence that Africa was once connected to South America?

• Cynognathus, Glossopteris, & Lystrosaurus

• Glossopteris, Cynognathus, & Mesosaurus

• Cynognathus, Mesosaurus, & Lystrosaurus

• Lystrosaurus, Mesosaurus, & Glossopteris

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NGSS.MS-ESS2-3

By studying the distribution of different types of fossils, geologists have determined that some plates have traveled great distances. Evidence to support this comes from the fact that--

• some fossilized organisms have only been found on one continent.

• the oldest known fossils, found in the deepest rock layers, represent ocean ridges.

• fossils of organisms that lived in warm climates have been foun din arctic environments.

• species of organisms in the fossil record have changed over geologic time.

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NGSS.MS-ESS2-3

The theory of plate tectonics was, at first, rejected by most scientists. Now most geologists accept that tectonic plates exist and that these tectonic plates can and do move. What is responsible for the change in how scientists think about plate tectonics?

• Tectonic plates have begun to move faster and faster over time.

• There are more people studying science now than in the past.

• Scientists can now travel underneath the plates and observe their motion.

• New evidence was discovered that made scientists revise their ideas.

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NGSS.MS-ESS2-3