Continental DriftContinental Drift

Continental Drift TheoryContinental Drift Theory

• Proposed by Alfred Wegener in 1912

• 250 million years ago, all of the continents were combined into one super-continent called “Pangaea”

• The continents gradually drifted apart to where they are today

Continental DriftContinental Drift

• Alfred Wegener’s hypothesis

- The hypothesis that Pangaea broke apart into continents.

Evidence to Support the TheoryEvidence to Support the Theory

““Puzzle PiecesPuzzle Pieces””

• Continents look like they could be part of a giant jigsaw puzzle

Distribution of FossilsDistribution of Fossils• Plant and animal fossils

found on the coastlines of different continents

• Mesosaurus (reptile that lives on land and fresh water) found in South America and Africa

• Glossopteris (plant) found on Africa, Australia, Asia, South America and Antarctica

Glaciers and RocksGlaciers and Rocks• Traces of glaciers

found in many tropical regions of Earth

• When continents drifted apart, glaciers melted away

• Glaciers leave tracks, scouring and polishing rock surfaces

RocksRocksSimilar rock structures found on

different continents:

- Rocks found in Appalachian

Mountains similar to rocks in

Greenland and western Europe

- Rock structures from eastern

South America similar to western

Africa

ClimatesClimates

• Fossils of warm-weather plants found on Spitsbergen (an island in the Arctic Ocean)

• Spitsbergen Island might have drifted to the Arctic from a tropical region of Earth

Problems With The TheoryProblems With The Theory

• Theory was not accepted by scientists because there was not enough evidence (NO PROOF!)

• Wegener could not explain what caused the continents to break apart and drift away

• He hypothesized that continents plow through the ocean floor or that the spinning of Earth on its axis was the cause

Homework (ISN)Homework (ISN)

* Write a 1 paragraph summary and draw a diagram about continental drift theory.