Volcanoes By: Amy Axelrood

Formation and Eruptions of Volcanoes Gas and buoyancy pressure push magma up against the earths crust Weak parts in the earth’s crust fracture and crack and the magma erupts out Eruptions can be violent and explosive or non-explosive http://www.geology.sdsu.edu/how_volcanoes_work/index.html

Types of Volcanoes There are four types of volcanoes Shield Volcano Cinder Cone Volcano Composite Volcano - Lava Domes

Shield Volcano Gently sloping Can be some of the largest volcanoes Is formed when thin layers of lava pour out of a vent and harden on top of previous layers Its profile looks like a warriors shield Created the Hawaiian Islands Mauna Loa

Cinder Cone Volcano Steep, cone shaped hill or mountain Materials build up around the edges to create a cone shape They have violent and explosive eruptions

Composite Volcano Tall, cone shaped mountains Layers of lava alternating with layers of ash Some examples are Mt. Fuji (left) and Mt. Saint Helens (next slide) Wider base than Cinder Cone

Mt. Saint Helens Lava Domes Due to the lava’s thick density and inability to flow the lava clogs the vent There is still pressure on the lava, but instead of flowing it domes up and hardens

Location