Continental Drift Theory • Alfred Wegener • German meteorologist • Found papers describing similar fossils on opposite sides of the Atlantic • Researched more cases of similar organisms separated by oceans • 1912 Proposed single supercontinent Pangaea
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Continental Drift Theory Alfred Wegener German meteorologist Found papers describing similar fossils on opposite sides of the Atlantic Researched more.
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Continental Drift Theory
• Alfred Wegener• German meteorologist
• Found papers describing similar fossils on opposite sides of the Atlantic
• Researched more cases of similar organisms separated by oceans
• 1912 Proposed single supercontinent Pangaea
Continental Drift Theory5 Types of Evidence
• Fit of the Continents• Distribution of Fossils• Sequence of Rocks• Glacier Scraping Patterns• Ancient Climates and
Wegener’s Continental Drift Evidence: Climate distribution
Past Present
Coal exists under the ice in the rock of Antarctica – yet coal can only form from plants that grow in warm climates.
Wegener’s Theory Problems
1) Wegener had no convincing mechanism (did not explain the forces) of how the continents might move. Continents plowing through the crust would destroy the crust.
2) Continents are not moving apart at the speed Wegener proposed.
Wegener = 250cm/yr
Actual = 2 cm/yr
Holmes Breakthrough: Heat trapped in the Earth caused
convection currents in the mantle.
• As a substance is heated its density decreases and rises to the surface until it is cooled and sinks again.
Convection Currents
• Gravity causes the heated mantle to sink
• The mantle heats up near the core and then rises again
• Conduction is the transfer of heat between 2 materials in direct contact with each other
• Cooling rate - slow• Crystal size - large• Density – less dense• Thickest portion of the Earth’s outer layer• Composition – made mainly of granite rock
• Cooling rate - fast• Crystal size - small• Density – more dense• Thinnest portion of the Earth’s outer layer• Composition – Made mainly of basalt rock
The Hawaiian-Emperor volcanic chain is the result of the drifting of the
Pacific Plate over a fixed hot spot.
http://geology.com/nsta/plate-tectonics-cover.gif
The bend in the (Hawaiian – Emperor) volcanic chain is the result of a major change in the direction of the movement of the Pacific Plate.
Location of Hot Spots
Hot spots result from hot, narrow plumes of material that rise deep within the mantle.
Plate Movement in the future• http://www.scotese.com/earth.htm
It is even possible to measure the speed of continentalplates extremely accurately, using satellite technology.
External Energy For Earth
• Sun & Moon keeps air and sea in motion, shapes surface
• Sun warms atmosphere & crust unevenly creating winds
• Winds drive ocean currents and water cycle• Erosion from winds, rains, rivers, glaciers, and
waves shape surface• Weathering from winds and rains• Sun & Moon Gravitational Energy, produces tides• Planetesimal collisions
Internal Energy for Earth
• Radioactive element decay
• Core heat from layers pressure
• Convection currents
• Volcanoes
• Hot Springs
• Earthquakes
Evidence for Plate Tectonics
• Continents fit together• Fossil distribution• Common rock formations: same age• Glacier evidence: deposits, striations, scraping• Climate distribution
New evidence • Magnetic pattern of rock• Location of earthquakes and volcanoes • Location of mountain ridges, rift valleys,