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Continental Drift Hypothesis Wegner believed continents had once been joined, and over time they drifted apart Pangaea – the first super-continent • Alfred Wegner 1912 Presented early fossil evidence • No evidence to explain how or why continents moved • Continental Drift Theory later developed into the

Pangaea – the first super-continent

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Continental Drift Hypothesis – Wegner believed continents had once been joined, and over time they drifted apart. Pangaea – the first super-continent. Alfred Wegner 1912 Presented early fossil evidence No evidence to explain how or why continents moved - PowerPoint PPT Presentation

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Page 1: Pangaea  – the first super-continent

Continental Drift Hypothesis – Wegner believed continents had once been joined, and over time they drifted apart

Pangaea – the first super-continent

• Alfred Wegner 1912Presented early fossil evidence• No evidence to explain how or why continents moved• Continental Drift Theory later developed into the theory of Plate Tectonics

Page 2: Pangaea  – the first super-continent

Evidence supporting Continental Drifta) Continental Puzzle –

continents fit togetherb) Matching Fossils -

matching fossils (Mesosaurus) on cross ocean landmasses

c) Mountain chains and rock type – (Appalachian)

d) Ancient climates – (ice core data, scratched bedrock)

Page 3: Pangaea  – the first super-continent

Plate Tectonics TheoryEarth's outermost layer, the lithosphere, is broken into 7

large, rigid pieces called plates: the African, North American, South American, Eurasian, Australian, Antarctic, and Pacific plates. Several minor plates also exist, including the

Arabian, Nazca, and Philippines plates. • plates are moving ~ 5 cm per year in different directions and speeds• The place where the two plates meet is called a plate boundary•Plates are crust and upper mantle

Page 4: Pangaea  – the first super-continent

Plate Boundaries and Actions

•Seafloor spreading produces new lithosphere •San Andreas Fault is an example of a Transform Fault•East African Rift Valley is an example of a divergent plate boundary•Himalayas are an example of convergent continental/continental plates

Page 5: Pangaea  – the first super-continent

Evidence and Testing for Plate Tectonics• Paleomagnetism –

changing patterns of magnetized rocks

• Earthquake patterns – link between plate boundaries and earthquakes

• Ocean Drilling - age of seafloor sediment– Newest (ridge crests)– Oldest (continental

edges)• Hot Spots – show plates

move over Earth’s surface (Hawaii)

Page 6: Pangaea  – the first super-continent

Cause of Plate Motion (tectonics)

• Heat convection in the mantle is the basic cause of plate movement

• Slab Pull and Ridge Push – downward convective flow of lithosphere (plate boundaries)

• Mantle Plumes – upward convective flow (volcanoes, hot-spots)