What is Lava dome?

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1. GiGi
   

   In volcanology, a lava dome or plug dome is a roughly circular mound-shaped protrusion resulting from the slow eruption of felsic lava (usually rhyolite or dacite) from a volcano, or from multiple lava episodes of different magma types. The characteristic dome shape is attributed to high levels of silica in the magma, causing the magma to be quite viscous and thick. The viscosity of the lava prevents it from flowing far from the vent that it extrudes from, causing it to solidify quickly and build on previous volcanic extrusions, creating a dome-like shape. Domes may reach heights of several hundred meters, and can grow slowly and steadily for months or years. The sides of these structures are composed of unstable rock debris. Due to the possibility of the building up of gas pressure, the dome can experience more explosive eruptions over time. When part of a lava dome collapses while it still contains molten rock and gases, it can produce a pyroclastic flow, one of the most lethal forms of a volcanic event. Other hazards associated with lava domes are the destruction of property, forest fires, and lahars triggered by pyroclastic flows near snow and ice. Lava domes are one of the principal structural features of many stratovolcanoes worldwide.
   Characteristics of lava dome eruptions include shallow, long-period and hybrid seismicity, which is attributed to excess fluid pressures in the contributing vent chamber. Other characteristics of lava domes include their spherical dome shape, cycles of dome growth over long periods, and sudden onsets of violent explosive activity. The average rate of dome growth may be used as a rough indicator of magma supply, but it shows no systematic relationship to the timing or characteristic of lava dome explosions.
   Some of the world's most famous active lava domes include those at Mount Merapi in Central Java of Indonesia, Soufrière Hills in Montserrat, and Mount St. Helens in Washington. Lassen Peak in northern California is one of the largest lava domes in the world and has the distinction of being the only other Cascade volcano besides Mount St. Helens to erupt (1914–1921) in the 20th century.

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