a. Hypothesized that all the continents were once joined together in a single landmass and have since drifted apart. b. This theory is called continental drift c. Wegener called this single continent Pangaea

a. Land Features that provide Evidence i. The outline of the continents fit together like a puzzle ii. The coal fields in North America and Europe are on the same plane (they are at the same place)

b. Evidence from Fossils i. Identical fossils are found on all different continents ii. This suggests that at one point all the continents were together 1. Example: Glossopteris (a fernlike plant) fossil was found in Africa, South America, Australia, India, and Antarctica

c. Evidence from Climate Change i. As a landmass moves closer to the equator it becomes warmer ii. As a landmass moves closer to the poles it becomes colder iii. However, in both situations, it will take its fossils with it 1. Example: Spitsbergen, an island in the Arctic Ocean has fossils of Tropical Plants a. This suggests that at one point in time this island was close to the equator

a. Sea-Floor Spreading occurs at the mid-ocean ridges i. Mid-ocean Ridges are long chains of under water mountains

b. Diagram

a. At these locations, part of the ocean floor sinks back into the mantle b. This process is called subduction c. This normally occurs between the oceanic crust and the continental crust i. Oceanic Crust is more dense and therefore sinks beneath the continental crust d. Subduction and Sea-floor spreading often work together

a. Earths lithosphere is broken into pieces called plates b. Different types of Boundaries between Plates i. Divergent Boundary: move away from each other ii. Convergent Boundary: move towards each other iii. Transform Boundary: plates slide against each other c. This theory says that the plates are in constant motion, driven by the convection current

i. This convection current occurs in the Mantle ii. Scientists can use satellite imaging to see how the plates have moved over time

a. These boundaries are called faults b. These faults allow the plates to move and also give way to volcanoes, mountain ranges, and deep ocean trenches

c. Divergent Boundary i. Move away from each other ii. Most occur along mid-ocean ridges iii. Some of these mid-ocean ridges rise above the sea level 1. This is called a rift valley iv. Sea-floor spreading occurs at these locations

d. Convergent boundary i. Move toward each other (or collide) ii. If an oceanic crust is converging with a continental crust, this will cause subduction 1. Oceanic crust are heavier than continental crust 2. This causes the oceanic crust to dive under the continental crust iii. If the same type of crust converges together, this creates mountain ranges iv. Most volcanoes occur at these subduction zones

e. Transform Boundary i. Move past each other ii. As these transform boundaries move past each other it causes an earthquake by sending out seismic waves iii. Crust is neither created or destroyed at transform boundaries