Published on Jan 19, 2020

Volcano Background Images

License Info: Creative Commons 4.0 BY-NC

Violent and devastating, legendary in history and mythology, volcanoes in action are among the most powerful forces of nature. They have shaped the Earth for billions of years and continue to do so, sometimes with deadly consequences to life and property.

Awesome to witness, erupting volcanoes are natural geologic structures providing a conduit to the Earth’s surface for the extrusion of molten rock materials migrating upwards from the depths beneath the Earth’s crust. Volcanoes can occur on land or on the seabed beneath the oceans.

Molten rock, or magma, to use its proper geological name for a body of molten rock found at depth, exists under pressure deep within the Earth. When overlaying solid rocks provide a channel, perhaps because of the constantly occurring internal adjustments of the surrounding rocks, the magma may escape to move upward to regions of lower pressure until eventually emerging at the surface, acquiring the new name: lava. On the other hand, magma that cannot find a outlet will become trapped at some sub-surface location for ever.


Magma and lava are similar but not the same. With the relief of pressure on the upward moving magma, much of the gaseous component is able to escape, thus changing its composition. This modified molten rock will emerge at the surface and then be called lava. In some cases the volcanic lava reaches the end of its upward journey with a volatile mixture of molten rock, gases, and water, expanding and exploding with such force that molten lava, rock fragments and ash are violently propelled into the air to great heights.

Active volcanoes release carbon dioxide and other gasses into the atmosphere, including significant amounts of water vapor. Volcanoes are not rare, and with tens of thousands of volcanoes erupting over the hundreds of millions of years of the planet’s early existence, the water vapor released by volcanoes provided the source of much of the Earth’s original oceans and much of its atmosphere.

Although the dramatic scenes of devastation resulting from volcanic eruptions capture our attention and imagination, volcanoes have also created many benefits for the young Earth. Volcanoes have produced gases that escape to warm the atmosphere and these gases contribute to the protective filtering of the Sun’s harmful radiation. Volcanoes provide fertilizer for the soil – most of which was derived from volcanic outpourings in the first place, they provide liquid in the form of water and nutrients and a habitat that helps make life possible. Volcanoes have created and are still creating all of the sea floor of the Earth’s oceans as a result of the outpourings at the mid-ocean ridges, those mountain chains that stretch around the globe, rising from the seabed. Most of the surface rocks and materials of the Earth’s crust are of volcanic origin. It is estimated that there are thousands of active volcanoes and also many dormant volcanoes that may re-awaken in the future. There are also many extinct volcanoes.

Volcanoes occur all over the Earth, but many are concentrated at the edges of continents, or beneath the sea where they form underwater volcanic mountain ranges, or long chains of islands such as those of Hawaii. A large number of active volcanoes encircle the Pacific Ocean basin and have acquired the name “Pacific Ring of Fire”. There is a particular reason for this configuration over thousands of miles and the explanation for this involves a well established geological theory known as Plate Tectonics – but that is a little too complex for discussion here. That same theory also explains the occurrence of volcanoes at the edges of continents.

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