Earthquakes, Volcanoes, and Tsunamis PDF

Earthquakes, Volcanoes, and Tsunamis  Earthquakes Fault: a break in the Earth’s crust. Tectonic Plates slide past each other along fault lines. Under stress suddenly breaks, a series of ground vibrations can be felt. These are seismic waves. These vibrations are...

Earthquakes, Volcanoes, and Tsunamis  Earthquakes Fault: a break in the Earth’s crust. Tectonic Plates slide past each other along fault lines. Under stress suddenly breaks, a series of ground vibrations can be felt. These are seismic waves. These vibrations are called earthquakes. Earthquakes occur everyday.  Focus & Epicenter The focus is the underground origin of an earthquake. Directly above the focus, on the Earth’s surface is the epicenter. Seismologists and Seismographs Seismologists study earthquakes. They can determine the strength of an earthquake using a seismograph (record of waves is called a seismogram). The Richter scale is used to calculate the strength of an earthquake.  The Richter Scale Used by scientists to quantify the amount of energy released by an earthquake, known as the magnitude. The scale goes from 1.0 to 10.0. Each increase of magnitude by one whole number is ten times greater in energy than the whole number below it. http://www.geo.mtu.edu/UPSeis/magnitude.html  Types of Earthquakes Convergent boundary: Here, one plate is forced over another plate during movement creating a thrust fault. Called Thrust Earthquake. Divergent boundary: Here, plates are forced apart. This kind is common in ocean floors where new floors are created. Called a Submarine Earthquake Transform fault: Unlike divergent and convergent, the plates here slip by each other. This is also called Strike-Slip Earthquake.  Tsunamis Japanese word for harbour wave. Generated from the displacement of water. Reach speeds of 700 to 800 km/hr. Reach heights of 30 meters +. A regular wave is generated by wind and tides.  Tsunami Diagram Wavelength Wave amplitude Trough Crest  Water Displacement 1 2 3 4  Tsunami Examples Research Indonesia 2004 and Japan 2011  Volcanoes A volcano is a mountain built from magma. Magma: melted rock that found beneath the surface of the earth (called lava when above) Located near tectonic plate boundaries where plates are sliding or separating from one another. Volcano Diagram  Volcanic Eruptions A volcano erupts when the pressure of the magma inside becomes so great that it erupts. Some volcanoes have magma flowing out of them all the time so the pressure never builds up. Ring of Fire.  Types of Volcanoes Different types of eruptions form different types of volcanoes. 1.Cinder cones: small and built of pyroclastic debris (rock). E.g. Arenal in Costa Rica 2.Shield: large and primary material is from lava flows. E.g. Hawaii 3.Composite (Stratovolcano): layers of lava flow and pyroclastic debris. E.g. Mount St. Helens Three Types  Cinder Cones Volcanoes made mostly of cinders and other rock particles that have been blown into the air are called cinder cones. Cinder cones form explosive eruptions. Because the material is loosely arranged, the cones are not high.  Shield Volcanoes Volcanoes composed of quiet flows are called shield volcanoes. Because it is runny, the lava flows over a large area. After several eruptions, a dome-shaped mountain is formed. Composite Volcanoes Volcanoes built up of alternating layers of rock particles and lava. They are formed by a violent eruption first, hurling volcanic bombs, cinder and ash out of the vent. Then a quiet eruption, produces lava flow that covers the rock particles.