Volcanoes are both feared and respected aspects of natural geography. The volcano is a direct link from the core of the planet to the outer crust. Most volcanoes occur around the edges of the tectonic plates. Hot spot volcanoes are different because they do not occur near the edges of a plate, but rather occur at quite a distance from the edges. The movement of these hot spots volcanoes can be tracked as well.
Plate tectonics is the accepted theory of how continents and geographical features are formed. These plates are both under the ocean and are visible continental plates. Volcanoes occur when the friction caused by the movement of the plates, through subduction, causes the rock to melt and rise to the surface. This can be accompanied by gases that can cause explosive eruptions. Other volcanoes erupt constantly and therefore do not have explosive results.
Oceanic Hot Spots
Hot spots are areas of heat where heat is not expected. This is due to the level of magma that is situated under the plate, pushing upwards. If the hot spot is under an oceanic plate, the hot spot can form a volcano called a shield volcano. This type of volcano builds in size as the lava being forced out cools and builds upon itself. This type of volcano can eventually grow large enough to break the surface of the water. This type of volcano formed the Hawaiian Islands.
Continental Hot Spots
Yellowstone and the surrounding areas are the result of a continental hot spot. The magma pushing up under the mantle of the continental crust causes calderas and the other volcanic structures seen along the Snake River. This includes the Old Faithful Geyser that is the result of heated water erupting out of a hole in the ground. These continental hot spots are also the causes behind the naturally heated springs of Japan.
Moving Hot Spots
Hot spots often appear to be moving because the motion of the plate on which it rests is so imperceptible. Hot spots do not move, but rather the plates move, causing the formations to move as well. The Hawaiian islands were formed this way. The first Hawaiian islands were thought to be originally much larger than their current state but have decreased in size due to the constant erosion caused by wind and water. A new island is currently being formed to the southeast of Hawaii.
Hot spot eruptions do differ from other volcanic eruptions in most cases. Hot spots often erupt continually and the lava creates basaltic rocks. There are cases in which the eruptions of hot spot volcanoes can be very explosive. This is due to the strength and weight of the rock and earth covering the volcano's mouth and the pressure accumulated by a lack of escape routes. Explosive eruptions also occur in the water when the lava is rapidly cooled, causing explosions to occur within the rock itself.