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Grade 7 Science Unit 4: The Earth’s Crust. Earthquakes, Volcanoes and Mountains. Earthquakes. The shaking of the Earth Measured using a seismograph The Richter Scale measures the strength of the earthquake.
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Grade 7 ScienceUnit 4: The Earth’s Crust Earthquakes, Volcanoes and Mountains
Earthquakes • The shaking of the Earth • Measured using a seismograph • The Richter Scale measures the strength of the earthquake
They are the result of energy released from forces built up due to plate tectonics in Earth’s crust • When this energy is released, it travels in seismic waves.
Local Earthquakes? • Usually minor in our region. They occur due to the movement along local faults on the floor of the Atlantic Ocean.
Volcanoes • An opening in Earth’s crust. Mt. St. Helens May 18, 1980 Washington
Paricutin February 20, 1943 Mexico
Mt. Pinatubo June 1991 Philippians
Kilauea November 24, 2007 Hawaii The most active volcano on Earth
Where Do Volcanoes Form? 1. At collision zones intense pressure can melt rock that later flows to the surface as a volcano (the Pacific Ocean is being subducted under Japan)
2. Where plates separate, molten rock flows up to the surface (Mid-Atlantic Ridge)
3. In area where the plates are thin, lava can be forced up through the cracks to the surface. (Hawaiian Islands)
Pacific Ring of Fire • The name given to the volcanoes encircling the Pacific Ocean.
Activity 11-2E: Patterns in Earthquake and Volcano Locations Page 386-7
Theories and Explanations In the Past... 1. Pele: Hawaiian goddess who makes the mountains shake and lava flow at Kilauea.
3. Anaxagoras: Greek who believed that volcanic eruptions were caused by great winds within the earth.
4. René Decartes: French philosopher who believed an incandescent earth core was the source of volcanic heat.
Mountain Formation • Due to: 1. folding 2. faulting 3. volcanic eruptions.
1. Folding... • A bend in rock layers. • Created when plates collide at convergent boundaries.
2. Faulting... • A break in rock layers. • When the rock is too brittle to fold. • Faulting can result from squeezing or stretching the Earth’s crust.
3. Volcanic Eruptions • When magma is forced up by pressure from deep within Earth, it can uplift the rock and create features on the surface. The magma may erupt as volcanoes.
