Classification of Volcano: Shape Pt 4 (final)

Acid or Dome Volcanoes

Internal structure of a typical lava dome
Source: http://pubs.usgs.gov/gip/volc/fig18.gif

Acid or dome volcanoes are steep-sided, convex cone because of the viscous (high silica content) lava which quickly cools and solidifies near the crater on exposure to air. The volcano grows largely by expansion from within, as indicated in the internal structure of the volcano by the layers of lava fanning upward and outward from the center. As it grows its outer surface cools and hardens. When part of a dome volcano collapses while it still contains molten rock and gases, it produces pyroclastic flow, one of the most lethal forms of volcanic event. Ultimately, many volcanic domes are destroyed by large explosive eruptions. Some domes form craggy knobs or spines over the volcanic vent, whereas others form short, steep-sided lava flows known as "coulees." Volcanic domes commonly occur within the craters or on the flanks of large composite volcanoes.

Volcanic dome atop Novarupta vent, Valley of Ten Thousand Smokes, Katmai National Park and Preserve, Alaska
Source: http://volcanoes.usgs.gov/Imgs/Jpg/Katmai/dds40-015_large.jpg

Next entry: Classification of Volcano by eruption style