In 1912, German scientist Alfred Wegener proposed the idea of continental drift. Based on evidence he saw, he believed that the continents must have been connected in the past, and then somehow “drifted” apart. Several things led him to believe this….
1. Continental shelves fit together like a puzzle
2. The same fossils were found on different continents.
3. The same rock formations were found on different continents.
4. Fossils from warm climates are found on continents that are frozen Fossils for this tree were found in Antarctica!
He had no mechanism! With the technological limitations at the time, he couldn’t find the evidence he needed to explain how his “continental drift” worked.
Theory that describes the interactions and movement of plates on the earth.
Earth’s lithosphere is broken into plates that move on the asthenosphere.
Explains why new crust forms on the ocean floor. Explains why earthquakes and volcanoes are likely to occur in particularly locations.
Mantle convection : Heat from the Earth’s inner and outer cores is transferred through the mantle by this process.
Two plates that are moving away from each other. Most divergent boundaries in the middle of the ocean at mid-ocean ridges, but they can be found on land at rift valleys.
Long chain of volcanic mountains on the ocean floor, where two plates are moving apart.
New rocks are formed in the middle and push the older rocks away from the ridge
Two plates are moving toward each other. A couple different things can happen, based on the types of plates… The 1 st one is: Subduction!
When one oceanic plate plunges under another plate. Forms deep sea trenches.
Subduction occurs due to density differences. Oceanic plates are made of basalt, which is more dense than continental plates that are made of granite. basalt granite
Volcanoes form at subduction zones. Can occur at the convergence of an oceanic plate with a continental plate, or an oceanic plate with another oceanic plate.
Oceanic-Continental: Cascade Mtns. Oceanic-Oceanic: Mariana Islands
Another type of CONVERGENT boundary! When two continental plates collide. Forms mountain ranges, such as the Himalayas, Appalachians, and Ural Mtns.
Colliding plates will form folded mountains at areas of continent-continent convergence.
Two plates are sliding past each other. Causes earthquake activity.
Check your mailbox Turn to page 6 of your Dynamic Earth packet to be stamped/checked Use your foldable from Weds to complete the features match warm up in your mailbox Complete your foldable (due on Monday): The sheet with the pictures is in the back of the classroom by the colored pencils if you need it.