A volcanic belt is a large volcanically active region. Other terms are used for smaller areas of activity, such as volcanic fields. Volcanic belts are found above zones of unusually high temperature () where

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...

is created by partial melting of solid material in the Earth's crust and

upper mantle The upper mantle of Earth is a very thick layer of rock inside the planet, which begins just beneath the crust (at about under the oceans and about under the continents) and ends at the top of the lower mantle at . Temperatures range from appr ...

. These areas usually form along

tectonic plate Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large te ...

boundaries at depths of . For example, volcanoes in

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

and western North America are mostly in volcanic belts, such as the

Trans-Mexican Volcanic Belt The Trans-Mexican Volcanic Belt ( es, Eje Volcánico Transversal), also known as the Transvolcanic Belt and locally as the (''Snowy Mountain Range''), is an active volcanic belt that covers central-southern Mexico. Several of its highest peaks h ...

that extends from west to east across central-southern Mexico and the

Northern Cordilleran Volcanic Province The Northern Cordilleran Volcanic Province (NCVP), formerly known as the Stikine Volcanic Belt, is a geologic province defined by the occurrence of Miocene to Holocene volcanoes in the Pacific Northwest of North America. This belt of volcanoes e ...

in western

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

. The deeply deformed and eroded remnants of ancient volcanic belts are found in volcanically inactive regions such as the Canadian Shield. It contains over 150 volcanic belts (now deformed and eroded down to nearly flat

plain In geography, a plain is a flat expanse of land that generally does not change much in elevation, and is primarily treeless. Plains occur as lowlands along valleys or at the base of mountains, as coastal plains, and as plateaus or uplands ...

s) that range from 600 to 1,200 million years old. These are zones of variably

metamorphosed Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causi ...

mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks incl ...

ultramafic Ultramafic rocks (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous and meta-igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are composed ...

volcanic sequences with associated

sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...

s that form what are known as greenstone belts. They are thought to have formed at ancient oceanic spreading centers and

island arc Island arcs are long chains of active volcanoes with intense seismic activity found along convergent tectonic plate boundaries. Most island arcs originate on oceanic crust and have resulted from the descent of the lithosphere into the mantle alon ...

terrane In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust (geology), crust fragment formed on a tectonic plate (or broken off from it) and Accretion (geology), accreted or "Suture (geology), sutured" to crust lying on another pla ...

s. The

Abitibi greenstone belt The Abitibi greenstone belt is a 2,800-to-2,600-million-year-old greenstone belt that spans across the Ontario–Quebec border in Canada. It is mostly made of volcanic rocks, but also includes ultramafic rocks, mafic intrusions, granitoid rocks, ...

Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central C ...

and

Quebec Quebec ( ; )According to the Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official name in Canadian English is one of the thirtee ...

is one of the world's largest greenstone belts. Volcanic belts are similar to a

mountain range A mountain range or hill range is a series of mountains or hills arranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similarity in form, structure, and alignment that have arise ...

, but the mountains within the mountain range are volcanoes, not mountains that are formed by

faulting In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

and

folding Fold, folding or foldable may refer to: Arts, entertainment, and media * ''Fold'' (album), the debut release by Australian rock band Epicure * Fold (poker), in the game of poker, to discard one's hand and forfeit interest in the current pot *Abov ...

by the collision of

tectonic plates Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large ...

Formation

Volcanic belts may be formed by multiple tectonic settings. They may be formed by subduction zones, which is an area on

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

where two

s meet and move towards one another, with one sliding underneath the other and moving down into the mantle, at rates typically measured in centimeters per year. An

oceanic plate Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic c ...

ordinarily slides underneath a continental plate; this often creates an

orogenic Orogeny is a mountain building process. An orogeny is an event that takes place at a convergent plate margin when plate motion compresses the margin. An ''orogenic belt'' or ''orogen'' develops as the compressed plate crumples and is uplifted t ...

zone with many volcanoes and

earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, fr ...

s. In a sense, subduction zones are the opposite of divergent boundaries, areas where material rises up from the mantle and plates are moving apart. An example of a subduction-zone related volcanic belt is the Okhotsk-Chukotka Volcanic Belt in northeastern

Eurasia Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelago ...

, which is one of the largest subduction-zone related volcanic provinces in the world, stretching some and comprising about of volcanic and plutonic material. Volcanic belts may also be formed by hotspots, which is a location on the Earth's surface that has experienced active

volcanism Volcanism, vulcanism or volcanicity is the phenomenon of eruption of molten rock (magma) onto the surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics, and volcanic gases erupt through a break in the surface called a ...

for a long period of time. These volcanic belts are called volcanic chains. Canadian

geologist A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes Earth and other terrestrial planets, as well as the processes that shape them. Geologists usually study geology, earth science, or geophysics, althoug ...

John Tuzo Wilson came up with the idea in 1963 that volcanic chains like the Hawaiian Islands result from the slow movement of a tectonic plate across a "fixed" hot spot deep beneath the surface of the planet, thought to be caused by a narrow stream of hot mantle convecting up from the mantle-core boundary called a

mantle plume A mantle plume is a proposed mechanism of convection within the Earth's mantle, hypothesized to explain anomalous volcanism. Because the plume head partially melts on reaching shallow depths, a plume is often invoked as the cause of volcanic hot ...

. But more recently some geologists, such as Gillian Foulger view upper-mantle convection as a cause. This in turn has re-raised the antipodal pair impact hypothesis, the idea that pairs of opposite hot spots may result from the impact of a large meteor. Geologists have identified some 40-50 such hotspots around the globe, with

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only state ...

Réunion Réunion (; french: La Réunion, ; previously ''Île Bourbon''; rcf, label= Reunionese Creole, La Rényon) is an island in the Indian Ocean that is an overseas department and region of France. It is located approximately east of the island ...

Yellowstone Yellowstone National Park is an American national park located in the western United States, largely in the northwest corner of Wyoming and extending into Montana and Idaho. It was established by the 42nd U.S. Congress with the Yellowston ...

, Galápagos, and

Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its s ...

overlying the most currently active. An example of a hotspot volcanic belt is the

Anahim Volcanic Belt The Anahim Volcanic Belt (AVB) is a west–east trending chain of volcanoes and related magmatic features in British Columbia, Canada. It extends from Athlone Island on the Central Coast, running eastward through the strongly uplifted and deeply ...

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

, which was formed as a result of the

North American Plate The North American Plate is a tectonic plate covering most of North America, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. With an area of , it is the Earth's second largest tectonic plate, behind the Pacific ...

sliding westward over the

Anahim hotspot The Anahim hotspot is a hypothesized hotspot in the Central Interior of British Columbia, Canada. It has been proposed as the candidate source for volcanism in the Anahim Volcanic Belt, a long chain of volcanoes and other magmatic features tha ...

.Volcanoes of Canada - Map of Canadian volcanoes
Retrieved on 2007-07-08 Most hotspot volcanoes are

basaltic Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of a ...

because they erupt through oceanic

lithosphere A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust (geology), crust and the portion of the upper mantle (geology), mantle that behaves elastically on time sca ...

(e.g., Hawaii, Tahiti). As a result, they are less explosive than subduction zone volcanoes, which have high water contents. Where hotspots occur under continental crust, basaltic magma is trapped in the less dense continental crust, which is heated and melts to form rhyolites. These rhyolites can be quite hot and form violent eruptions, despite their low water content. For example, the

Yellowstone Caldera The Yellowstone Caldera, sometimes referred to as the Yellowstone Supervolcano, is a volcanic caldera and supervolcano in Yellowstone National Park in the Western United States. The caldera and most of the park are located in the northwest corn ...

was formed by some of the most powerful volcanic explosions in geologic history.

Examples

Andean Volcanic Belt The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed as a result of subduction of the Nazca Plate and Antarctic Plate underneath the South American ...

Garibaldi Volcanic Belt The Garibaldi Volcanic Belt is a northwest–southeast trending volcanic chain in the Pacific Ranges of the Coast Mountains that extends from Watts Point in the south to the Ha-Iltzuk Icefield in the north. This chain of volcanoes is located in ...

* Taupo Volcanic Zone *

References

{{Volcanoes Volcanology Plate tectonics

Formation

Examples

See also

References