Continental Drift The Earth on the Move

Continental Drift  Most scientists used to believe the Earth to be a place that undergoes little change.  Oceans and land masses have been in their places since the beginning of time.

Alfred Wegner  Saw evidence that the continents moved and were not locked in place like other scientists thought.  Proposed a radical new idea called continental drift.  Stated that the continents “plow” through the sea.

Wegner’s Evidence 1. Continental Jigsaw Puzzle 2. Fossils that Match Across the Sea 3. Rock Types and Structures Matches 4. Ancient Climates

Continental Jigsaw Puzzle  With the development of more accurate maps, scientists started to notice how the continents fit together.  Wegner proposed that this is because they once were together.

Fossil Match  Fossils found in one area matched fossils found across the sea. 1. Cynognathus 2. Glossopteris 3. Lystrosaurus 4. Mesosaurus

Rock Types  Rock structures are similar in places that seemed to be connected at one time.  Mountain belts that end in the ocean begin across the sea (Appalachian Mts. and Caledonian Mts.)

Ancient Climates  Evidence exists of Glaciers in the southern hemisphere and of tropical environments in the northern hemisphere.  Was this from moving poles or moving plates?

What came from this evidence?  The continental drift hypothesis and Pangaea.  Pangea—meaning 1 world.  The idea that 300 million years ago, all the continents were once formed into a huge super continent.

Where was the evidence?  Opponents of Wegner said that there was no “mechanism” to make continental drift possible.  Wegner’s idea of the continents “plowing” through the sea seemed improbable.  Wegner’s ideas were not considered reliable until a bit later…