Answer:
Lava Domes
(By C. Tienrey, 2010)
Introduction
Lava domes, which may also be referred to as volcanic domes, are common features in volcanic regions throughout the world. Lava domes can come in many shapes and sizes, and while they may not be quite as spectacular as their explosive or flowing counterparts, they are often still an awe inspiring sight to see. The purpose of this page is to provide a brief introduction to lava domes, which will by no means be entirely comprehensive. In fact, even today, there is still much unknown about lava domes and what they can potentially reveal about volcanic systems.
Lava domes are formed by viscous magma being erupted effusively onto the surface and then piling up around the vent. Like lava flows, they typically do not have enough gas or pressure to erupt explosively, although they may sometimes be preceded or followed by explosive activity. However, unlike lava flows, the lava that forms domes is often to thick and sticky to flow very far, and thus instead pile up thick and high around the vent.
Answer:
a lava dome is a circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions on earth are lava dome forming. Less sluggish types are gradational to lava flows and are sometimes referred to as dome flows or coulées. Lava domes have compositions ranging from basaltic andesite to rhyolite, although most are composed of crystal-rich dacite.
