Lava dome

A lava dome is a round mound.

It comes from a volcano. The hot rock is very thick and sticky. This thickness keeps the rock from flowing far.

Because it stays in one place, it grows into a hill. Some domes grow for many years. Some even grow for hundreds of years!

These mounds can be very tall. They are a special part of many volcanoes.

A lava dome is a round mound of rock.

It forms when thick lava pushes out of a volcano. This lava has high viscosity. Viscosity means the lava is very sticky. Because it is so sticky, it cannot flow far. Instead, it piles up into a dome shape.

Domes can grow in two ways. They can grow from inside. This happens when new magma enters the dome. They can also grow on the outside. This happens when new lava lands on the surface. Some domes grow for months or years. Some even grow for centuries!

Domes can also be dangerous. Gas can build up inside them. This can cause big explosions. If a dome breaks, it can make a pyroclastic flow. This is a fast cloud of hot gas and rock. Sometimes, a dome can form under the ground. This is called a cryptodome. It can make the side of a volcano bulge outward. This happened at Mount St. Helens in 1980.

A lava dome is a round, mound-shaped pile of rock.

It forms when very thick lava pushes out of a volcano. This lava has high viscosity, which means it is very sticky. Because it is so sticky, the lava cannot flow very far away. Instead, it stays near the vent and piles up into a dome shape.

About 6% of all eruptions on Earth create these domes. They are important parts of many stratovolcanoes around the world.

There are two ways a dome can grow larger. The first way is called endogenic growth. This happens when new magma flows into the inside of the dome. The second way is called exogenic growth. This is when new bits of lava land on the outside surface.

A dome can also grow a tall shape called a lava spine on its top. This spine can make the whole dome less stable. Domes can grow for months, years, or even centuries. For example, the Mount Merapi volcano has grown for a very long time.

Scientists have studied many different types of lava domes. The type of rock in a dome can change. Some domes are made of basalt, like the one at Semeru in 1946. Most domes are made of intermediate rocks like dacite or andesite. Some are made of rhyolite, which has a lot of silica.

The Chaiten volcano in Chile had a rhyolite dome in 2010. Scientists use the speed of dome growth to guess how much magma is moving. However, the growth speed does not tell them when an explosion will happen.

Lava domes can be quite dangerous to people nearby. Gas can build up inside the sticky lava. This pressure can cause sudden, violent explosions. If a part of the dome collapses, it can create a pyroclastic flow.

These are fast clouds of hot gas and rock. Domes can also cause forest fires or lahars. A lahar is a flow of loose ash and debris. Some domes even form hidden underground. These are called cryptodomes, and they can make a volcano bulge outward.

We can find evidence of these shapes in many places. Some domes are found in northern Chile, like the huge Chao dacite dome complex. This is a type of dome called a coulée that has flowed a bit.

We can even see evidence of domes on other worlds. Scientists think there might be domes on the Moon, Venus, and Mars. On Mars, they may be in places like Arcadia Planitia. This shows that the same forces that shape Earth also shape the rest of our solar system.

A lava dome is a circular, mound-shaped protrusion found on volcanoes.

These structures form through the slow extrusion of highly viscous lava. Viscosity refers to how thick or sticky a liquid is. Because the lava is so viscous, it cannot flow far from the volcanic vent. Instead, it piles up in place to create a dome shape. About 6% of all eruptions on Earth result in the formation of lava domes. They are major structural features of many stratovolcanoes across the globe.

The specific shape of a dome is caused by the properties of the magma. High viscosity can happen in two different ways. First, the magma may have high levels of silica. Second, the magma may undergo degassing, which is the loss of gas from the fluid. Most preserved domes consist of rhyolite or dacite because they have high silica content. Domes made of basalt or andesite tend to weather quickly. These less silica-rich domes also break apart easily when more fluid lava enters the system.

Lava domes grow through two distinct processes known as endogenic and exogenic growth. Endogenic growth occurs when magma flows into the interior of the existing dome. This makes the dome expand from the inside out. Exogenic growth happens when new, discrete lobes of lava are placed upon the surface.

Sometimes, a dome can grow a tall feature on its top called a lava spine or spire. These spines can increase the instability of the entire structure. Domes can grow steadily for many different lengths of time. Some grow for months, like Unzen volcano, while others grow for centuries, like Mount Merapi.

The dynamics of these domes are often unpredictable and non-linear. This unpredictability is caused by crystallization and outgassing within the conduit. As the lava cools and solidifies, it can create complex internal structures. Domes undergo constant changes, including growth, collapse, solidification, and erosion. Scientists monitor seismicity to understand these changes. They look for shallow, long-period, and hybrid seismic activity. This activity is linked to excess fluid pressures within the vent chamber.

Lava domes can present significant hazards to the surrounding environment. Because gas pressure builds up intermittently, domes can trigger sudden, violent explosive eruptions. If a portion of the dome collapses, it can expose pressurized magma. This event can produce pyroclastic flows, which are fast-moving clouds of hot gas and rock.

Other dangers include forest fires and lahars. A lahar is a flow created by the re-mobilization of loose ash and debris. Gravitational collapse can also produce a block and ash flow.

Sometimes, magma accumulates at a shallow depth without breaking the surface immediately. This creates a hidden structure called a cryptodome. The name comes from the Greek words for "hidden" or "secret."

Cryptodomes can cause the side of a volcano to bulge outward. This bulging can lead to a sector collapse. Such a collapse can cause explosive decompression of the subterranean magma. This process was observed during the 1980 eruption of Mount St. Helens and the 1956 eruption of Bezymianny.

There are also specialized forms of domes, such as coulées. A coulée is a lava dome that has experienced some flow away from its original position. These landforms look like a mix between a dome and a lava flow.

The Chao dacite dome complex in northern Chile is the world's largest known dacite flow. This massive complex shows obvious flow features like pressure ridges. Scientists have also found evidence of dome-like structures on other planets. These include the Moon, Venus, and Mars. On Mars, these structures may exist in the western Arcadia Planitia or within Terra Sirenum.