The Effects of Plate Tectonics

1. The Effects of Plate Tectonics

2. What Is Plate Tectonics • On the inside of the Earth there is a sea of molten magma. • Continental plates float on the “sea”. • The plates are always in motion as they drift along. • Pangaea separated long ago to the place the continents are now.

3. Rifts and Trenches • In the oceans are rifts where magma comes from inside the Earth. • Rifts are found where two plates come together. • The rising magma pushes the ocean plates apart. • Trenches are places where the ocean plates slip under the continental plates. • As the upper part of the plate moves outward toward the trench, the lower part moves back toward the rift. • The process of making the new plate and getting rid of the old is called Subduction.

4. Oceanic Plate Movement

5. Mountains of Fire • Most volcanoes are located along rifts or faults where plates come together. • Pressure builds up from heat and pressure of plates. • Pressure is released eventually as an eruption, throwing magma in the air and sending lava flowing. • There are four types of volcanoes. • Cinder cones are made from mostly volcanic ash. • Composites are made from alternating layers of ash and pyroclastic flows (lava). • Shield volcanoes are very big and broad formed mainly from pyroclastic flows. • Lava domes are bubbles of hardened lava with liquid magma centers. • Here are some PDF files about volcanoes.

6. Fault + Stress = Earthquake • Two continental plates come together at a fault and begin to push on each other • Over time (usually several years), the plates build up pressure against each other. • Eventually, so much pressure builds up that the plates buckle or slip past each other. This is an earthquake.

7. Types of Faults • (A) is known as a transform fault or slip fault since the plates slip past each other. More on transform faults here. • (B) is a divergent fault. The plates here move apart or diverge from each other. More on divergent faults here. • (C) is a convergent fault. Its plates come together until one goes under the other one. More on convergent faults here

8. Summary • Giant plates under the continents • Pangaea broke up due to continental drift. • Rifts and trenches in the ocean floor where new and old sea floor is made and destroyed (Subduction) • Plates come together at faults. • Four types of volcanoes occur at faults and rifts. • Earthquakes happen when too much stress is put on a fault which is then released. • There are three types of faults where earthquakes occur.