Why are convergent volcanoes more explosive

Volcanoes form here in two settings where either oceanic plate descends below another oceanic plate or an oceanic plate descends below a continental plate. This process is called subduction and creates distinctive types of volcanoes depending on the setting:.

Volcanoes can form at subduction zones where tectonic plates are moving towards each other and one plate descends beneath the other. This illustration shows ocean-continent subduction. Subduction provides a mechanism for introducing water-bearing sediments into the mantle. It is this process that allows the generation of magma at depth that feeds volcanoes that are formed at the surface. Note: There is a third setting of destructive boundary: continent-continent.

Here, the pushing together of two continental plates results in the mountain forming processes that shaped, for example, the Alps and Himalayas. Volcanoes can also form above a column of superheated magma called a mantle plume. This may happen in areas that are distant from plate boundaries. It is also referred to as hot spot or intraplate volcanism. Heat from the mantle plume causes melting and thinning of the crust, which leads to volcanic activity at the surface.

Over millions of years, the Pacific Plate has moved over the hot spot, creating a chain of volcanic islands. This simple schematic diagram shows the movement of the tectonic plate light brown over a mantle plume, or hot spot, to produce a chain of volcanic islands. The superheated magma rises through the mantle yellow , melts the crust above brown and flows on to the surface forming a volcano.

Diagram not to scale. Discovering Geology introduces a range of geoscience topics to school-age students and learners of all ages. In this case, there is so much water that the temperature is reduced to a point where amphiboles can crystallize. How common such superhydrous magmas are remains an open question.

Though Shiveluch is known to be a special case in terms of its activity, it is possible there are superhydrous magmas in volcanoes all over the world. Exploring the most explosive volcano in the world By Shawn Ballard. Researchers are able to sample different eruptive events over time from layered flows around Shiveluch. The coexistence of specific minerals on the surface reveals superhydrous conditions within the volcano.

Using microbes to make carbon-neutral fuel. These eruptions have given Mount Rainier the classic layered structure and conic shape of a composite volcano. Volcan de Fuego and Acatenango are a pair of stratovolcanoes that stand more than 3, meters 12, feet above sea level near Antigua, Guatemala. While the volcanoes are considered twins because of their similar shape and size, they are made of different types of lava and have distinct eruption histories.

While Acatenango erupts infrequent ly today, Fuego is considered to be the most active volcano in Central America, erupting more than 60 times since Shield volcano es are built almost exclusive ly of lava, which flows out in all directions during an eruption. These flows, made of highly fluid basalt lava, spread over great distances and cool in thin layers. While they are not as eye-catching as their steep stratovolcano cousins, shield volcanoes are often much larger in volume because of their broad, expansive structure.

Shield volcanoes make up the entirety of the Hawaiian Islands. The Galapagos Islands are also made up of a series of shield volcanoes. Isabela and Fernandina islands have flatter tops than other shield volcanoes because lava erupts from fissures around their tops and along ridges at their bases.

Pyroclastic cone s are the most prolific type of volcano on Earth. They can develop as part of stratovolcanoes, shield volcanoes, or independently. Also known as cinder cone s, they form after violent eruptions blow lava into the air. Often formed from a single eruption or short series of eruptions, pyroclastic cones only stand at heights of tens of meters to hundreds of meters.

It was the first volcano to be studied for its entire life cycle. In that time, lava and ash buried the nearby town of San Juan. Lava dome s are like shield volcanoes in that they are built entirely of lava. This lava, however, is too thick and sticky to move great distances.

It just piles up around the volcano vent. Lava domes are often found on the summit or flank s of a volcano, but they can also develop independently. Like pyroclastic cones, they only reach a few hundred meters, as they are formed during singular eruptions or slow lava releases. For almost a year, a lava dome grew out of a summit crater created from the eruption, reaching a height of more than meters 1, feet. It ultimately collapse d into a pile of rubble after 11 months of growth. Some volcanoes experience such large, explosive eruptions that they release most of the material in their magma chamber.

This causes the land around the erupting vent or vents to collapse inwardly, creating circular depression s called calderas. Depending on their intensity and duration , volcanic eruptions can create calderas as much as kilometers wide. Crater Lake, Oregon, is in a caldera about 10 kilometers 6 miles wide. The volcano's magma chamber collapsed, then filled with water from rain and snow, creating the lake.

Crater Lake is the deepest lake in the United States. Deception Island, located off the coast of Antarctica, experienced a violent eruption roughly 10, years ago. The volcano summit collapsed, forming a caldera 7 kilometers 4. The caldera gives Deception Island its horseshoe shape, which opens to the sea through a narrow channel.

Much like calderas, craters are depressions left after a volcano experiences a large eruption. While calderas are formed by the collapse of material inside a volcano, craters are formed as materials explode out from a volcano. Craters are usually much smaller than calderas, only extending to a maximum of about one kilometer. Many volcanoes have multiple craters caused by different eruptions.

The Maly Semiachik volcano, located on the Kamchatka Peninsula in far eastern Russia, has six craters at its summit. The youngest of these craters, Troitsky, filled in with water and snowmelt, creating a lake meters feet deep. The lake is highly acid ic, as volcanic gas es continue to be released into the water from the active volcano below. Lava lake s are also found in volcanic craters.

Erta Ale, a volcano in Ethiopia, has a lava lake in its summit crater. Lava lakes are where magma has bubbled up to the surface and pooled in a crater. Volcanic eruptions are as diverse as volcanoes themselves—which is to say, very diverse! Some of the ways volcanologists have classified these eruptions are based on the heights they reach, the types of materials they eject , and the explosiveness of these ejections.

Hawaiian eruption s are the calmest eruption type. They are characterized by steady lava eruptions known as lava fountain s or fire fountains. Lava fountains are able to reach heights of up to 2 kilometers 1. The highly fluid lava associated with Hawaiian eruptions flows easily away from the volcano summit, often creating fiery river s and lakes of lava within depressions on the surrounding landscape.

These eruptions are named after the Hawaiian Islands, where they most often occur. Kilauea, which has been erupting continuously since , has produced lava flows covering more than square kilometers 37 square miles on the island of Hawaii.

These flows continuously destroy houses and communities in their path, while also adding new coastline to the island. Strombolian eruption s are characterized by short-lived outbursts of lava rather than steady fountaining. The lava is thicker and has a higher gas content than that of Hawaiian eruptions. Large gas bubbles rise from the magma chamber, pushing the pasty lava upward until the bubbles explode at the summit vent. These explosions can reach heights up to 10 kilometers 6.

Strombolian eruptions are named after the Mediterranean island of Stromboli, Italy. Considered by many to be the most active volcano on Earth, Stromboli has been erupting almost continuously for 2, years. Vulcanian eruption s are short-lived but much more explosive than Strombolian eruptions. Very thick lava causes gas pressure to build up in the magma chamber. When this pressure is finally released it creates canon-like explosions that can travel faster than meters per second miles per hour.

Lava, rock, and ash are propelled up to 20 kilometers These plume s of material have the ability to drift moderate distances away from the eruption site. Composite volcanoes have the following characteristics:. Shield volcanoes are found on divergent plate boundaries , where two plates move away from one another.

Shield volcanoes have the following characteristics:. Ash released from shield volcanoes often builds up around the vent forming a steep, round hill known as a cinder cone.