Lava Dome Formation

Lava dome formation occurs when magma too viscous to flow far, typically silica-rich dacite or rhyolite, is extruded at a vent and piles up over and around it rather than spreading into a lava flow, building a steep-sided mound directly above the conduit. A growing dome is unstable and prone to collapse, which can trigger fast-moving pyroclastic flows and block-and-ash flows down the volcano flank, the mechanism behind some of the deadliest eruptions in recorded history, including Mont Pelee in 1902. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/