Presentation on theme: "Continental Drift Theory Alfred Wegener German meteorologist Found papers describing similar fossils on opposite sides of the Atlantic Researched more."— Presentation transcript:
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 Theory 5 Types of Evidence Fit of the Continents Distribution of Fossils Sequence of Rocks Glacier Scraping Patterns Ancient Climates and Wandering Polar Regions
Wegener’s Continental Drift Evidence: Continents ‘fit’ together in a single land mass 250 mya CLICK Simulations ey.edu/geology/anim1. html ey.edu/geology/anim1. html
Wegener’s Continental Drift Evidence: Plant and animal fossils of the same species were found on several different continents.
Wegener’s Continental Drift Evidence: Similar sequence of rock or rock formations have the same age
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 library.thinkquest.org/C003124/images/convect.jpg Click animation
Volcanic rocks on the seafloor have magnetization because, as they cool, magnetic minerals within the rock align to the Earth’s magnetic field. New Evidence: Magnetic pattern of rock
North Magnetic Pole in No. Hemi
North Magnetic Pole in So. Hemi
Present Day North Magnetic Pole in No. Hemi
Sea-Floor Spreading Hypothesis by Hess & Deitz CLICK Animation:
Plate Tectonics Theory Plates ‘float’ on the Asthenosphere Plates have oceanic and continental crust
Continental Crust Cooling rate - slow Crystal size - large Density – less dense Thickest portion of the Earth’s outer layer Composition – made mainly of granite rock
Oceanic Crust Cooling rate - fast Crystal size - small Density – more dense Thinnest portion of the Earth’s outer layer Composition – Made mainly of basalt rock
Volcano - opening or rupture in the Earth’s crust that allows molten rock to escape og%20Resources/Images/Plate%20Tectonics/Plate%20Tectonics/VolcanoStructure.jpg
Earthquake - result of sudden energy release in the Earth’s crust creating seismic waves.
More Evidence: Location of mountain ridges, rift valleys, mid-ocean ridges, and trenches on plate boundaries. Convergent, Divergent and Transform SIMULATIONS ON ALL BOUNDARY TYPES CLICK
Andes Mountains Convergent Oceanic & Continental Plates move toward each other blue.utb.edu/paullgj/images/Conv_Cont_Ocean.JPG CLICK A trench, a steep walled valley on the sea floor, forms here. Denser oceanic crust subducts under less dense continental crust
Evidence - Location of earthquakes and volcanoes
The Hawaiian-Emperor volcanic chain is the result of the drifting of the Pacific Plate over a fixed hot spot.
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 It is even possible to measure the speed of continental plates 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, mid-ocean ridges, and trenches First evidence used for Continental Drift Theory