Write two differences between a volcanic mountain and a residual moutain
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Answer:
Residual mountains are those mountains which have been eroded by the agents of degradation such as winds, rain, frost and running water. The hard rocks that are left behind are called residual mountains. The Sierras of central Spain and Mesas of USA are some examples of residual mountains
Mountains are formed when 2 continental plates converge, ie push up against each other. Italy was part of the African Plate which pushed north into Southern Europe (and is still doing so.) Because continental plates are too light to subduct, they keep pushing. The rock caught between these 2 plates is squeezed and having nowhere else to go, is pushed sideways and up. Cut through one and you would find that it is solid rock all the way through.
Volcanos — (a) One type of volcano, called a stratovolcano on the other hand, is formed when an oceanic plate collides with a continental plate. The oceanic plate is denser and thus heavier than the continental plate, and thus is pulled down under the continental plate into the mantle. As it descends, it partially melts, and the melted material (called magma) pushes up into the earth’s crust, breaking the rock. As it breaks the surface, it spews out this molten magma onto the surface as lava and ash and thus a volcano is formed. This cools to form what looks like ordinary rock, although inside boiling hot magma continues to push up through the original break in the crust into the volcano to form what is called a vent. Inside this vent (which is rather like a chimney) the magma rises and as it does so it searches out weaknesses in the rock and forms secondary vents. This could be likened to a hand. The wrist is the main vent, the fingers of the hand secondary vents. (b) While a stratovolcano is most people’s idea of a volcano, there is a second type of volcano. Shield volcanoes are so called because while they resemble mountains to a certain extent, they are shaped, as the name suggests like a shield, with gently sloping sides. These are formed by a mantle plume rather than a subducting plate, but the method of formation is the same.
Also most volcanoes have a crater, a circular depression or hole in the top of the volcano. Mountains do not. They have a peak at the summit. Also mountains do not have lava lakes which are exactly what the name suggests, lakes of lava. (once magma breaks through into the open, it is called lava). Neither do mountains emit steam or gases from fumaroles (cracks in the crater, which can be very small when the volcano is quiet.)
Some volcanos, called calderas, are huge depressions in the ground. These, such as Yellowstone, or Italy’s Campi Flegrei, do not look like mountains, but are formed like all volcanoes, by the upwelling of magma. This type of volcano was once as described above, a mountain-like structure, but after an explosive eruption has caused the ground to collapse. They do not look in the slightest like mountains and indeed, as with Yellowstone can be surrounded by mountains. Also, they have boiling hot pools of water and mud. Also, in the case of Campi Flegrei, they emit Sulphur Dioxide gas, which smells like rotten eggs and which leaves a yellow mineral deposit around the edges of the pools. Here no one can mistake the volcano for a mountain!
Explanation: