Volcanoes I. Molten rock Magma

Molten rock
a. Magma- beneath the Earth’s surface
b. Lava- magma that is on the surface of the Earth
i. Pahoehoe- (pa-hoy-hoy)- freely flowing lava that forms a thin skin with wrinkles and
then looks like twisted rope when solid
ii. Aa- (ah-ah)- rough, jagged surface with dangerously sharp edges
Types of Cones
a. Shield Volcanoes-built by a steady supply of very fluid basaltic lava. Have a broad, gently
sloping cone that resembles a shield.
i. Mauna Loa in Hawaii- largest volcano on earth
ii. Caused by a Hot Spot (high magma temps. Causing volcanoes)
b. Stratovolcano - (Composite Cone) erupts both lava and ash with steep sides
i. Erupts explosively
ii. Mt. Vesuvius, Mount Pele, Mnt. St Helens, Mt. Pinatubo
Craters- the central vent of a volcano.
i. Calderas-very large crater > 5km in diameter
1. Yellowstone N.P.a. old volcano that erupted 600,000 yrs ago.
i. Hot springs, bubbling mud, steaming pools, geysers