We know that the continents were joined together 300 and 350 million years ago because...

...Glossopteris fossils were found on all continents.

Why are the oldest rocks on the ocean floor so much younger than continental rocks?

Ocean plates are forced below plates that they collide with

The shapes of the continents tell us...

...that the continents may have been joined together.

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Measuring Up Lesson 30: How do we Know That the Earth's Tectonic Plates have Moved Over Time?

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Review questions to go along with pages 187 to 190 in the 8th Grade Science Measuring Up.

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Answers

1
__, or preserved organisms, are used by scientists use to reconstruct Earth's history.
Mountain rocks
Fossils
Shapes of the continents
Maps of the ocean
2
Scientists first began speculating that the continents were once joined together in the __.
1900s
1700s
1970s
1500s
3
We know that the continents were joined together 300 and 350 million years ago because...
...Cynognathus fossils were found on all continents.
...Lystrosaurus fossils were found on all continents.
...Glossopteris fossils were found on all continents.
...Mesosaurus fossils were found on all continents.
4
Why are the oldest rocks on the ocean floor so much younger than continental rocks?
Ocean plates are forced below plates that they collide with
It's more difficult to determine the age of ocean rocks
Oceans were formed millions of years after the continents
Ocean rocks are melted and destroyed by underwater volcanoes
5
What is the average rate of the Atlantic sea floor separating?
2 m/per
2 mm/year
2 km/year
2 cm/year
6
____ are formed when plates drift apart allowing magma to rise and create new crust.
Natural statues
Mid-ocean ridges
Tectonic plates
Mid-ocean islands
7
Mid-ocean ridges are actually chains of underwater ___!
Canyons
Rivers
Volcanoes
Mountains
8
The shapes of the continents tell us...
...that plate movement eroded them.
...that ocean plates are forced below continental plates.
...that new rock is created along mid-ocean ridges.
...that the continents may have been joined together.
9
There are several __ on Earth that are made of the same rocks, but are on different continents.
mountain ranges
fossils
tectonic plates
riverbeds
10
A ___ is a region between two tectonic plates that are moving apart on an ocean floor.
trench
mid-ocean ridge
continental divide
riverbed

Measuring Up Lesson 30: How do we Know That the Earth's Tectonic Plates have Moved Over Time? Flashcards | StudBud