How do shield volcanoes erupt

Types of volcano - composite and shield There are two main types of volcano - composite and shield. Composite volcanoes Composite volcanoes are found on destructive plate margins , where the oceanic crust sinks beneath the continental crust. Composite volcanoes have the following characteristics: Acidic lava , which is very viscous sticky.

Steep sides as the lava doesn't flow very far before it solidifies. Alternate layers of ash and lava. For this reason, they're also known as stratovolcanoes. Shield volcanoes are the largest volcanoes on Earth that actually look like volcanoes i. The Hawaiian shield volcanoes are the most famous examples. Shield volcanoes are almost exclusively basalt, a type of lava that is very fluid when erupted.

For this reason these volcanoes are not steep you can't pile up a fluid that easily runs downhill. Shield volcanoes are the result of high magma supply rates; the lava is hot and little-changed since the time it was generated. Shield volcanoes are the common product of hotspot volcanism but they can also be found along subduction-related volcanic arcs or all by themselves. Here are 4 of the volcanoes that comprise the big island of Hawai'i.

The most recent eruption was in Lava domes are built up when the lava is too viscous to flow , according to the U. A bubble or plug of cooling rock forms over a fissure. This cooler, thick lava usually rises near the end of an explosive eruption and lava domes often form within the craters of stratovolcanoes.

Helens has several well-defined lava domes inside the crater , according to NASA. Besides well-known symmetrical volcanoes such as Mount Fuji in Japan and Kilimanjaro in Tanzania, volcanic activity is responsible for several other distinctive landforms. Calderas : A caldera is a bowl-shaped depression formed when a volcano collapses into the void left when its magma chamber is emptied. There are three types , according to San Diego State University.

The first type is a crater lake caldera. This is the result of a stratovolcano collapsing into its magma chamber during a violent eruption. Basaltic calderas have a concentric ring pattern resulting from a series of gradual collapses rather than a single event.

They are often found at the summit of shield volcanoes such as the craters at the tops of Mauna Loa and Kilauea.

Resurgent calderas are the largest volcanic structures on Earth. They are the result of catastrophic eruptions that dwarf any eruptions ever recorded by human beings. Yellowstone caldera, sometimes called a "super volcano," is one example. Volcanic plugs : When magma solidifies in the fissure of a volcano the hard dense rock may form a " neck " that remains when softer surrounding rock has been eroded away, according to the U.

Tuff cones : also known as maars, tuff cones are shallow, flat-floored craters that scientists think formed as a result of a violent expansion of magmatic gas or steam, according to the U.

Maars range in size from to 6, feet 60 to 1, meters across and from 30 to feet 9 to meters deep, and most are commonly filled with water to form natural lakes. Maars occur geologically young volcanic regions of the world such as the western United States and the Eifel region of Germany.

Lava plateaus : Shield volcanoes may erupt along lines of fissures rather than a central vent spilling liquid lava in successive layers. Over time as these layers form broad plateaus such as the Columbia Plateau, according to the Encyclopedia Britannica. These plateaus are often cut by deep canyons that expose the layers of rock.

It has erupted dozens of times in the past 2, years, according to the Encyclopedia Britannica. The A. The volcano sent a cloud ejecta into the atmosphere that was more than four times the amount ejected by Mount Pinatubo in , leading to the " Year Without a Summer " of in Europe and North America, according to a paper in Wiley Interdisciplinary Reviews: Climate Change. Seventy-pound boulders landed on islands 50 miles away, and a foot tsunami devastated hundreds of villages, including Java and Sumatra, according to San Diego State University.

About 36, people died.