CONTINENTAL DRIFT SEAFLOOR SPREADING THEORY OF PLATE TECTONICS Plate Tectonics.
Continental Drift to Plate Tectonics and Earth’s Structure
15
Continental Drift to Plate Tectonics and Earth’s Structure
description
Continental Drift to Plate Tectonics and Earth’s Structure. Continental Drift and Alfred Wegener. Wegener's Hypothesis In 1912, a German scientist named Alfred Wegener proposed a hypothesis that is now called continental drift . - PowerPoint PPT Presentation
Transcript of Continental Drift to Plate Tectonics and Earth’s Structure
Continental Drift to Plate Tectonics and Earth’s Structure
Continental Drift and Alfred Wegener
Wegener's HypothesisIn 1912, a German scientist named Alfred
Wegener proposed a hypothesis that is now called continental drift.
Wegener hypothesized that the continents once formed part of a single landmass called a supercontinent named PANGEA or “One Earth”
Compiled years of evidence on expeditions around the world and died in Greenland.
Pangea
Similar Mountains and Fossils Continents Apart
Evidence of Different Climates
Wegener’s Theory Rejected
Wegener suggested that the continents plowed through the rock of the ocean floor. However, this idea was shown to be physically impossible.
Wegener couldn’t find any mechanism for how or why plates moved around the globe.
Continental drift ultimately rejected and Wegener died in 1930 while on an expedition in Greenland.
But then…! Theory of Plate Tectonics!
In 1947, researchers (Harry Hess) began mapping the ocean floor.
Mid-Ocean ridge discovered and mapped.
Mid-Ocean Ridge Discoveries
1.) Sediment thinner at ridge than farther out on either side. What does this mean about the age of rocks at the ridge compared to further toward the continents?
2.) Sediment and rocks are younger at the ridge than further out towards continents.
What does this mean?New crust is forming at the ridge and moving
outward on either side of the ridge suggesting plates move.
Magnetic Striping
Mechanism Found! Convection Cycles
Theory of Plate TectonicsTheory that explains how and why plates move.
Layers of the Earth
Layers Crust-Like the shell of an egg is very thin (roughly 5km thick).
Mostly Silica and Oxygen. Very brittle. Lithosphere: Includes crust and upper mantle. A tectonic plate
is made of lithosphere. Mantle: Dense, hot layer of semi-solid (like liquid plastic) rock.
Mostly iron and magnesium. Like the white part of a boiled egg. Asthenosphere: Makes up lower mantle. Liquid Outer Core: Spins and makes earth’s magnetic field.
Made of iron and nickel. Solid Inner Core: Made solid by tons of pressure. Extremely hot
and made of iron and nickel. Like the yolk of an egg.
