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Volcano Formation

This is a drawing of magma percolating up through the crust, causing the volcano to expand prior to eruption.

Volcanoes form when hot material from below rises and leaks into the crust. This hot material, called magma, comes either from a melt of subducted crustal material, which is light and buoyant after melting, or it may come from deeper in the interior of a planet and is light and buoyant because it is *very* hot.

Magma, rising from lower reaches, gathers in a reservoir, in a porous region of overlying rock called the magma chamber. Eventually, but not always, the magma erupts onto the surface. Strong earthquakes accompany rising magma, and the volcanic cone may swell in appearance, just before an eruption, as illustrated in this picture. Scientist often monitor the changing appearance of a volcano, especially prior to an eruption. The different reasons why a volcano forms are

• via plumes or hot spots in the lithosphere
• as a result of subduction of the nearby lithosphere

This is a drawing of magma rising up through the crust, causing the volcano to expand prior to eruption.

Volcanoes form when hot material from below rises and leaks into the crust. This hot material, called magma, comes either from a melt of subducted crustal material, and which is light and buoyant after melting, or it may come from deeper in the interior of a planet and is light and buoyant because it is *very* hot.

Magma, rising from lower reaches, gathers in a reservoir, in a weak portion of the overlying rock called the magma chamber. Eventually, but not always, the magma erupts onto the surface. Strong earthquakes accompany rising magma, and the volcanic cone may swell in appearance, just before an eruption, as illustrated in this picture. White arrows in the picture show the volcano getting bigger as magma rises inside. Scientist often monitor the changing shape of a volcano, especially prior to an eruption. The different reasons why a volcano forms are

• via plumes or hot spots in the lithosphere
• as a result of subduction of the nearby lithosphere

This is a drawing of magma making it's way up through the crust, causing the volcano to expand prior to eruption.

Volcanoes form when hot material from below rises and leaks into the crust.

The hot material, called magma, rising from lower ground, gathers in a reservoir called the magma chamber. Eventually, but not always, the magma erupts onto the surface and forms lava. Strong earthquakes accompany rising lava, and the volcano may swell just before an eruption, as shown in this animation.

White arrows in the picture show the volcano getting bigger as the lava rises inside. Scientist measure the swelling of a volcano before an eruption.

The different reasons why a volcano forms are

• when bubbles of material rise to the surface
• when the crust is forced to go down