Earthquakes
Earthquakes are vibrations made from rock breaking under stress. This happens when tectonic plates slide past one another. The surface where the plates slip is called the fault or fault plane. The location beneath the earths surface where the earthquake starts is called the hypocenter and the location above the earth's surface is called the epicentre.
Tectonic plates move around, bump and slide past each another. The edges of the plates are called plate boundaries. Plate boundaries are made up of faults. Most earthquakes that we have on earth happen on these faults. This is because the edges of the plates are rough. This causes the plates to get stuck for a while. When they finally break free all the stress built up releases, resulting in an earthquake. Occasionally earthquakes have foreshocks. These are smaller earthquakes that occur before larger earthquakes. The main earthquake, which is the largest, is called the mainshock. After the mainshock we experience an aftershock. After shocks occur in the same place as the mainshock. Unfortunately aftershocks can last up to years. Although this is dependant on the size of the mainshock. |
Volcanoes
A volcano is an opening vent on the crust. When a volcano erupts magma comes out from deep in the earth. How much a volcano explodes is dependent on the gas within the magma and how easily the magma can flow. There are three types of volcanoes. They are called Shield, Composite and Caldera.
Shield: A shield volcano is one one the three types. The volcano itself is a snide flattened dome-like shape. The reason it is shaped like this is because layers of lava flow over the surface of the volcano and cool. From this volcano lava flows easily across great distances. Although it does move very slow, any human could out run or walk the magma. The type of magma from a shield volcano is called basaltic magma, which has temperatures from 800 to 1200 degrees celsius. Composite: When a composite volcano erupts it results in an explosion. The type of magma that it releases is thick and sticky because the magma is cooler. Inside a composite volcano lies the reason to why it explodes. Pressure starts to build up which makes magma foam and violently explode. This all results in lava flows, pyroclastic flows (hot ash clouds) and lahars (dangerous mud flows). Andesitic is the name of the type of magma in this volcano which has temperatures of 800 to 1000 degrees celsius. Caldera: This is the most dangerous volcano, one of the reasons being is that it is extremely explosive. When it has erupted it partly or entirely empties the underlying magma chamber. Because the magma is too heavy the volcano often sinks or collapses. These volcanos are very rare. They hold magma called rhyolitic, which is 650 to 800 degrees celsius. |
Sheild Volcano
Composite volcano
Caldera volcano
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