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Earthquakes 1. 2. 3. 4. 5. Earthquake: the shaking and trembling that result from the movement of rock beneath Earth’s surface. Seismic waves carry the energy of the earthquake away from the focus, through Earth’s interior and across the surface. There are 3 categories of seismic waves; p-waves, s-waves, and surface waves. The 1st to arrive are the primary waves, or p-waves. P-waves are earthquake waves that compress and expand the ground like an accordion. S-waves or secondary waves are earthquake waves that vibrate from side to side as well as up and down. Surface waves move more slowly than p-waves and s-waves, but they can produce severe ground movements. Some surface waves make the ground roll like ocean waves. Focus; the point beneath the Earth’s surface where rock that is under stress breaks, triggering an earthquake Epicenter: the point directly above the focus on the surface Fault: is a break in the crust where slabs of crust slip past each other. Hazards of earthquakes; shaking of the earth, power lines fall, gas line burst, fires, and building falling. To determine where an earthquake occurred you need to find the difference in the arrival of p-waves and s-waves from 3 different stations. Use the chart to determine the distance around the station center. Draw a circle around the station center. Where the 3 circles meet is where the earthquake occurred. Volcanoes 1. Shield Volcano; thin layers of lava pours out of a vent and hardens on top of a previous layer. The lava flows gradually build a wide, gently sloping mountain. Form from a hot spot. Quiet eruptions. Cinder Cone: when cinders erupt explosively from a volcanic vent, they pile up around the vent, forming a cone shaped hill. Composite: lava flow alternates with layers of ash, cinders, and bombs, which has both quiet and explosive eruptions. Tall cone shaped mountain. 2. Shield- quiet Cinder cone-explosive Composite- quiet and explosive 3. Most volcanoes occur along diverging plate boundaries, such as mid-ocean ridge or in subduction zones around the edge of oceans. Some volcanoes can form at hot spots. 4. High in silica: very thick, light colored, lower in temperature, cause explosive eruption Low in silica: thin, dark colored, hotter in temperature, cause quiet eruptions 5. Hot spring form when a body of water is heated up from magma. It makes it way to the surface through a crack in the rock. 6. Hazards of volcanoes lava, pyroclastic flow, fire, gases