Shop Windows to the Universe

Warnings: The True Story of How Science Tamed the Weather by Mike Smith tells the story of our storm warning system. See our online store book collection.
This is a drawing of magma percolating up through the crust, causing the volcano to expand prior to eruption.
Click on image for full size

Volcano Formation

Volcanoes form when hot material from below risesand 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 monitorthe changing appearance of a volcano, especially prior to an eruption. The different reasons why a volcano forms are

  • via plumesor hot spots in the lithosphere
  • as a result of subduction of the nearby lithosphere
Last modified April 29, 2016 by Jennifer Bergman.

Shop Windows to the Universe Science Store!

Windows to the Universe Community



You might also be interested in:

Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more


A mantle plume is a bubble of material which rises to the lithosphere from the deep interior of the planet. The plume is the red portion shown in the drawing to the left. Such plumes are thought to form...more

Magma Chamber

Magma consists of remelted material from Earth's crust and fresh material from the aesthenosphere, relatively near the Earth's surface. When magma is erupted onto the surface in the form of lava, it becomes...more

Plume Volcanism

The Hawaiian Islands are an example of the way some volcanoes are made. A rising hot plume of material makes it's way to the lithosphere of the Earth from the deep interior, and erupts material unto the...more


When two sections of the Earth's lithosphere collide one slab of lithosphere can be forced back down into the deeper regions of the Earth, as shown in this diagram. This process is called subduction....more

Mid-Ocean Spreading Ridge

As the Earth cools, hot material from the deep interior rises to the surface. Hot material is depicted in red in this drawing, under an ocean shown in blue green. The hotter material elevates the nearby...more

Mountain Building

Mountains are built through a general process called "deformation" of the crust of the Earth. One example of deformation comes from the process of subduction. When two sections of the Earth's lithosphere...more

Volcanic Ash

Ash is made of millions of tiny fragments of rock and glass formed during a volcanic eruption. Volcanic ash particles are less than 2 mm in size and can be much smaller. Volcanic ash forms in several ways...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA