The shapes of the continents tell us...

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

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

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

...Glossopteris fossils were found on all continents.

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

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