continental drift. continental drift theory proposed by alfred wegener in 1912 250 million years...
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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.