Review: Relative Dating and Continental Drift.

By Teacher at IS 93

The earth moves!

Our earth moves! We have many pieces of evidence for this some we can even feel; like earthquakes. So what is causes the movement? Magma! Deep in the Earth, molten rock churns as it heats and cools in convection currents. This moves the crustlike plates on top, and even creates and new and destroys old plates. *VIDEO TIME*

​If an intrusion or a fault cuts through existing rocks, the intrusion/fault must be YOUNGER than the rock it cuts through.

Think About it: Can you cut a cake or put icing on before the cake is made?

Layers of the Earth show us:

• its history

• fossils of animals and plants from long ago

Rock layers in different places can be correlated, or matched up, by matching the rocks and fossils in the layers.

​

Correlation

Continental Drift

Alfred Wegener

German meteorologist who first proposed the theory of continental drift.

Pangea

The large
landmass

that

included

all of

Earth’s
present-

day

continents

Evidence for

Continental Drift

1. Shape of the Continents

● The continents fit together like puzzle pieces.
● 1858: Antonio Pelligrini depicted Africa & South

America connected.

2. Fossils

● Fossils of the same organisms were found on

different continents.

● Mesosaurus found in Africa & South America,

but couldn’t swim across the ocean.

3. Rock Evidence

● Existing mountain

ranges separated by
oceans had identical
mineral content.

● Example: Appalachian

mountains in US &
Caledonian mountains in
British Isles

5. Coal Deposits

● Coal deposits found in temperate & polar regions

even though coal is formed in tropical regions.

Evidence #6 - Glacial Scars in Africa!

Theory:

The reason for Continental Drift: Convection Currents in the Mantle