A volcano is a location on the surface of the earth where magma has erupted out of the interiori of the planet. Magma is a molten rock, which has melted from the extreme heat (2200 C to 5000 C) and pressure that exists inside the earth. Once molten rock has erupted onto the earth's surface, it is called lava. As lava spreads out on the surface, it cools and becomes solid rock again. The buildup of lava forms hills and mountains on land, and it forms islands if the volcano began on the ocean floor. The Hawaiian Islands, for example, exists because of volcanoes.
Volcanoes are classified as active or inactive. Inactive volcanoes are older and have usually erupted many many times. A volcano is described as active if it is currently erupting or expecting to erupt eventually.
A volcanic eruption occurs when lava, gasses, and other subterranean matter come out of the ground. The exact location of where they come out is called a vent. A volcano usually has more then one singular vent.
Eruptions can be violent, but they also can be quiet. Some eruptions send lava high above the surface in spectacular fountain shapes. Quiet eruptions consist of lava simply flowing out of vents. Both eruptions can also have gasses, such as sulfur and fluorine, coming out of the vents. If you want a more in depth description of the volcanic eruption stages, either check out the model below or click here!
Even after a volcano stops erupting, gasses and vapors are still released. Some volcanoes, however, can end one period of eruptions and begin another after many years. Eventually, the volcano reaches the cooling stage. When the volcano cools, it reduces in size from water and weather erosion.
Well, there are quite a few volcanoes in the U.S. The list below labels 5 known volcanoes in the United States. However, to find more then just these 5 volcanoes.. Click here to learn about more volcanoes around!
