The Earth in Motion

1. The Earth in Motion

2. Our lithosphere is made up of many large plates – Oceanic and Continental • The plates are moving several cm/yr. • As the plates move, the continents also move or “drift,” over Earth’s surface. • German Scientist, Alfred Wegener , used fossil evidence to prove the continents were “drifting” and once formed a massive supercontinent called Pangea.

3. Continued… • The idea that the plates are in constant slow motion (drifting) is known as continental drift.

4. Rock Stress • The movement of Earth’s plates creates powerful forces that squeeze or pull the rock in the crust. • These forces cause a stress on the rock. • Shearing, tension, and compression work over time to change the shape and volume of rock.

5. Plate Tectonics • The motion of the plates also explains how they interact producing… • mountain ranges (uplift), earthquakes, volcanoes, and features on the ocean floor.

6. Uplift • The forces of plate movement can build up Earth’s surface. Over millions of years, fault movement can cause uplift, changing a flat plain into a towering mountain range or plateau. Mt. Everest in the Himalayas

7. Earthquakes are a reminder that the Earth’s crust is in constant motion. • An earthquake is what happens when two blocks of the earth suddenly slip past one another.  The surface where they slip is called the fault or fault plane.

8. Volcanoes • During a volcanic eruption, the gases dissolved in magma rush out, carrying the magma with them. Once magma reaches the surface and becomes lava, the gases bubble out. • An erupting volcano can trigger tsunamis, flashfloods, earthquakes, mudflows and rock falls. website

9. Volcano Hazards • During a quiet eruption, lava flows pour from vents, setting fire to and then burning everything in their path. • During an explosive eruption, a volcano can belch out hot, burning clouds of volcanic gas, ash, cinders, and bombs.

10. Stages of a Volcano • An active, or live, is one that has erupted recently or volcanologists see the possibility of an eruption soon. Active volcanoes are watched very closely!

11. A dormant, or sleeping, volcano is like a sleeping bear it has been quiet for a long time, but still has signs it may erupt again. A volcano becomes dormant when the vent is blocked by hardened lava, called a plug, or if the magma seeps back under the earth’s crust. Mt. St. Helens after 5/18/80

12. An extinct, or dead, volcano is unlikely to erupt again. It hasnot erupted for thousands of years. Sometimes it is hard to tell if a volcano is dormant or extinct. They will be listed as dormant until volcanologists are sure there will no more eruptions. Shiprock, the erosional remnant of the throat of an extinct volcano. (NM)

13. There are more than 500 active volcanoes in the world. More than half of these volcanoes are part of the "Ring of Fire." Kilauea volcano in Hawaii. Sicily, Italy Volcanic “cone”

14. Zone of frequent earthquakes and volcanic eruptions that circles the basin of the Pacific Ocean. It is associated with a continuous series of oceanic trenches, island arcs, volcanic mountain ranges and plate movements.