This is a story of 1 Hypothesis and the theory that replaced it 1. In 1915 a German scientist named Alfred Wegener proposed the hypothesis of continental drift Even though he had collected much evidence, this idea wasn’t well accepted 2. By 1968 new discoveries lead to the development of the Theory of Plate Tectonics. These new discoveries gave the scientific community the evidence they needed to understand how Wegener’s hypothesis could be possible.

9.1 Continental Drift An Idea Before Its Time Wegener’s continental drift hypothesis: continents once formed a single supercontinent. • Proposed Pangaea began to break apart 200 mya. -Pangaea means: “All land”

Breakup of Pangaea

The Evidence for Continental Drift 1) The Continental Puzzle

The Evidence for Continental Drift 2) Matching Fossils - several organisms found on different landmasses.

3) Rock Types & Geological Formations - several mountain belts end at one coastline, then reappear on a landmass across the ocean.

The Evidence for Continental Drift Ancient Climates -There is evidence of ancient glaciers in many different parts of the world that line up when Pangaea is reconstructed.

Glaciation

9.1 Continental Drift Rejecting the Hypothesis  A New Theory Emerges • Main problem with Wegener’s idea – no feasible explanation of what made continents move.  A New Theory Emerges In 1968 new technology lead to important findings - new theory called plate tectonics emerges. SONG Better song