Volcanic activity is the main process by which material from the Earth's interior reaches its surface. Volcanoes played a huge role in the formation of the Earth's atmosphere, oceans, and continents. "When the earth was new, the superheated gases within it (including carbon dioxide) streamed out through countless volcanoes to form the original atmosphere and oceans." Volcanoes can be found on land and under the ocean (where they are called seamounts). Volcanoes are labeled by their periods of acvtivty. If a volcano is erupting, it is called active. If a volcano is not presently erupting but may at some point in time, it is called dormant. Extinct volcanoes, are volcanoes that have stopped erupting forever. Normally, volcanoes are labeled extinct when no eruption has been noted in recorded history.
The Earth's crust is broken into many rigid plates that "float" on the surface of the planet and they are referred to as plate tectonics. The plates will move if there is intense pressure created by movements of currents carrying heated energy from the center of the planet to the surface. When this happens it causes pressure which in turn make the plates move toward or away from each other (and sometimes past each other in up and down motions). Volcanoes form on land near coastal areas when a continental (land) plate and an oceanic plate converge or move towards each other. Oceanic plates are denser, they sink beneath the surface, where extremely high temperatures and pressure cause the rocks to melt. This will make hot magma that then will rise towards the surface and when the magma reaches the crust it will collect in the magma chamber. When this happens pressure inside the chamber will exceed that of the verlying rock, and magma is forced upward through cracks in the Earht's crust.
The Earth's crust is broken into many rigid plates that "float" on the surface of the planet and they are referred to as plate tectonics. The plates will move if there is intense pressure created by movements of currents carrying heated energy from the center of the planet to the surface. When this happens it causes pressure which in turn make the plates move toward or away from each other (and sometimes past each other in up and down motions). Volcanoes form on land near coastal areas when a continental (land) plate and an oceanic plate converge or move towards each other. Oceanic plates are denser, they sink beneath the surface, where extremely high temperatures and pressure cause the rocks to melt. This will make hot magma that then will rise towards the surface and when the magma reaches the crust it will collect in the magma chamber. When this happens pressure inside the chamber will exceed that of the verlying rock, and magma is forced upward through cracks in the Earht's crust.