Plate Tectonic Notes 2/7/19

Alfred Wegner Came up with idea that at one point in our history our continents were all one giant land mass, called Pangea. He then concluded that the large mass of land separated into two continents, Gondwanaland and Laurasia. His theory that continents shift overtime is called CONTINENTAL DRIFT. He had several pieces of evidence to show that the continents moved.

Alfred Wegner’s 4 Clues to Continental Drift He had 4 clues that he used to explain continental drift! Puzzle Pieces Fossils Rock Strata Coal

1. Puzzle Pieces It fits like a puzzle! Different continents appear to be able to fit together like a puzzle. When they are all pushed together it forms PANGEA

2.Distribution of Fossils Fossils of the same exact reptile were found on different continents. When the continents split different life forms developed on each continent. That is why we don’t notice similarities in today’s animals!

3. Rock Strata Correlation The age and layering of the rock strata is identical in specific areas suggesting that at one time they were touching. The distribution of rocks in Earth’s crust is a direct result of tectonic activity.

4. Coal Formations Coal formations have been found in cold and dry climates when coal can only form in warm wet climates. Like wise fossil remains of oceanic life have been found in the very top of mountain peaks.

Why didn’t they believe him? Looking at all of the evidence surely they would believe him! No! The greater scientific community didn’t because he couldn’t fully explain his WHY these things happened. He had evidence that it was happening, but he didn’t know exactly how the plates were moving.

Harry Hess Harry was using sonar to research for the U.S. Navy when he realized that the ocean was shallowest in the center. This doesn’t make much sense that it is shallowest in the center and deepest right off our coasts, so....... He concluded that the crust must be created from the center, but how? So he got in a submarine and started researching. He found that hot less dense material below the Earth’s crust rises toward the surface at mid-ocean ridges Hess named this idea, SEAFLOOR SPREADING.

Tectonic Boundaries Boundaries are where two tectonic plates meet.

Divergent Boundary Where two plates are moving apart Creates new land Mid-Atlantic Ridge

Seafloor Spreading New seafloor is formed when magma is forced upward toward the surface at a mid-ocean ridge Can only occur at a divergent boundary

Tension Forces that pull rocks apart Causes a NORMAL Fault

Convergent Boundary Where two plates come together and collide Mountains and volcanoes

Convergent Boundaries Ocean meets Continent: Ocean goes below Continent Continent meets Continent: Collide make a mountain Ocean meets Ocean: Collide one breaks

Subduction Zone SUBduction Zone occurs when a plate SUBmerges under another plate Can only occur at a convergent boundary

Compression Forces that push or squeeze rocks together Causes a REVERSE Fault

Transform Boundary Where two plates slide past each other Earthquakes San Andreas Fault

Shearing Forces that cause rocks on either side of the faults to push in Causes a STRIKE SLIP Fault

How do we know plate tectonics are real? Distribution of fossils (aka Alfred Wegner) Earthquakes Continental and Ocean Floor Features Mountains Volcanoes Faults Trenches

Ring of Fire An area in the Pacific Ocean where there is a lot of volcanic and earthquake activity happening.

Volcano The vent as well as the mountain that forms around it from cooled lava, ash, cinders, and rock

Vent Magma is released through these in Earth’s crust