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Earthquakes and Volcanoes A Rocky Relationship. Earthquakes. Earthquakes. earthquake. An __________ is the shaking and trembling that results from the movement of rock beneath Earth’s surface. Moving plates squeeze and pull the crust Earthquake video (3 min) Stress: Shearing Tension
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Earthquakes earthquake • An __________ is the shaking and trembling that results from the movement of rock beneath Earth’s surface. • Moving plates squeeze and pull the crust • Earthquake video (3 min) • Stress: • Shearing • Tension • Compression
Vocabulary Check • Deformation: any change in volume or shape to Earth’s crust • Fault: a break in the crust where slabs of crust slip past each other
Shearing • Stress that pushes a mass of rock in two opposite directions • Shearing creates _________ faults. • Ex: San Andreas fault NORTH AMERICAN PLATE PACIFIC PLATE strike-slip
Tension • Stress that pulls on the crust, stretching rock so that it becomes thinner in the middle • Tension causes _______ faults. • Rio Grande rift valley in New Mexico normal
Tension • The red line marks equivalent layers on opposite side of the fault. HANGING WALL FOOT WALL
Compression • Stress force that squeezes rock until it folds or breaks. • Produce _______faults. • Rocky mountains in Montana reverse
Compression • You can tell by the rock layers that the footwall has sunk below the hanging wall. HANGING WALL FOOT WALL
Parts of an Earthquake The epicenter is the point on the surface directly above the focus. The focus is the point beneath the surface where the rock under stress breaks and causes an earthquake.
Seismic Waves • During an earthquake seismic waves race out from the focus in all directions. • Seismic waves carry the energy of an earthquake: • - away from the focus • through the interior • across the surface
Measuring Earthquakes • A __________ records the ground movements caused by seismic waves. • Magnitude: measurement of earthquake strength based on seismic waves and movement at faults • Mercali, Richter, Moment Magnitude • Seismology video (3 min) seismograph
Earthquake Hazards • Damage/ destroy buildings and bridges • Topple utility poles • Fracture gas and water mains • Liquefaction • Tsunamis (6 min) • Aftershocks (1 min) • Earthquake Safety (2 min)
EARTHQUAKE VIDEO (20 MIN)
Volcanoes • A weak spot in the crust where molten material, or ______, comes the surface. • Volcanoes form: • at plate _________. • underwater at: • Diverging plate boundaries • Subduction zones • Converging boundaries magma boundaries
What about the volcanoes that aren’t at plate boundaries? • The ___________is a major volcanic belt around the Pacific Ocean. Ring of Fire
Hot Spot Volcanoes hot spot • A _______ is an area where magma from deep within the mantle melts through the crust. • As plates drift over the hot spot in earth’s crust, a series of islands can form, like the ________Islands in the Pacific. • Yellowstone National Park (4 min) • Hawaiian Islands (2 min) Hawaiian
Once it reaches the surface, the pressure is released with the lava and gases in a quiet or loud explosion. Magma carries gases up with it, and it is under extreme pressure. Liquid magma is less dense than the rock that surrounds it, so it flows up through the cracks…
Stages of a Volcano • Active (live) • Erupting or may erupt in the near future • Dormant (sleeping) • Will erupt again, but may be a very long time • Extinct (dead) • Unlikely to erupt again
Can it happen here? • Why are volcanic eruptions unlikely in GA? • Why are so many volcanoes located in the western part of the U.S.?
VOLCANO VIDEO (27 MIN) THE MAGIC SCHOOL BUS BLOWS ITS TOP VIDEO (24 MIN)