Volcanic Landforms

Topics: Volcano, Lava, Magma Pages: 2 (719 words) Published: November 23, 2010
Volcanic Landforms

Volcano is essentially a fissure or vent (opening) which serves as an outlet for hot magma from beneath the Earth’s crust. The hot liquid magma coming out in the form of lava (most commonly molten basalt) is potential of shaping different landforms on earth crust. The most common landforms that are results of volcanic activity include cones, craters, calderas, domes etc. This article gives a description of these volcanic landforms. SHIELD VOLCANOES- These are characterised by gentle upper slopes. The slope varies from only 5 degrees to 10 degrees. The shield volcanoes are made up of mainly thin lava flows around central vent. The low viscosity lava (low silica content) travels down gently and as it cools down it creates less steeper lower slope. These are also found at the flanks of bigger volcanoes like Kilauea is situated on the Hawaiian shield volcano. STRATOVOLCANOES- These are characterised somewhat steeper slopes (30 degrees to 40degees) near the vent and the summit due to highly viscous lava flows are not able to travel long distances before they cool down. The less steeper slopes at the base is due to erosional activity. The show inter layering of pyroclastic material and thus sometimes also called composite volcanoes. Pyroclastic material make upto 50% of a stratovolcano. They show a long time of repose which makes them quite dangerous. CINDER CONES- They are small volume cones build up by fall deposites around the eruptive vent. There slope is around 25-30 degrees. During later stages of eruptions the lava may come out from the flanks. Cinder and tephra cones usually occur around summit vents and flank vents of stratovolcanoes. MAARS- The magma heats up the groundwater and converts it into vapours which builds up pressure and results in eruptions containing water and pre-existing rocks. Walls of crater fall back into crater and fills it with loose material. If the crater depth reaches below the water table of the region, the...
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