2.  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….

3.  1. Continental shelves fit together like a puzzle

4.  2. The same fossils were found on different continents.

5.  3. The same rock formations were found on different continents.

6.  4. Fossils from warm climates are found on continents that are frozen  Fossils for this tree were found in Antarctica!

7.  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.

8.  Theory that describes the interactions and movement of plates on the earth.

9.  Earth’s lithosphere is broken into plates that move on the asthenosphere.

10.  Explains why new crust forms on the ocean floor.  Explains why earthquakes and volcanoes are likely to occur in particularly locations.

11.  Mantle convection : Heat from the Earth’s inner and outer cores is transferred through the mantle by this process.

13.  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.

14.  Long chain of volcanic mountains on the ocean floor, where two plates are moving apart.

15. New rocks are formed in the middle and push the older rocks away from the ridge

17.  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!

18.  When one oceanic plate plunges under another plate.  Forms deep sea trenches.

19.  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

20.  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.

21.  Oceanic-Continental: Cascade Mtns.  Oceanic-Oceanic: Mariana Islands

22.  Another type of CONVERGENT boundary!  When two continental plates collide.  Forms mountain ranges, such as the Himalayas, Appalachians, and Ural Mtns.

23.  When two plates collide, there is a lot of stress: ▪ The measure of the amount of force applied over an area

24.  Compression: Rock layers are squeezed inward

25.  Tension: Rock layers are being stretched

26.  Shear stress: Rock layers are pushed in two opposite directions.

27.  Anticline: An up fold in the rock layers  Syncline: A down fold in the rock layers

30.  Mountains often form along continental margins, the boundary between continental crust and oceanic crust.  - Active margins occur along plate boundaries  - Passive margins are not along plate boundaries

31. - Mountains that are along active margins are younger than mountains found on passive margins.

32.  The type depends on the collision…  Colliding plates will form volcanic mountains at areas of ocean-continent convergence, or ocean-ocean, because of melting that occurs to the subducting plate.

33.  Colliding plates will form folded mountains at areas of continent-continent convergence.

34.  Two plates are sliding past each other.  Causes earthquake activity.