VOLCANOES

TECTONICS  Earth’s crust is divided into plates.  Convection currents in Earth’s mantle causes the plates to move.  Plate movement results in earthquakes and volcanoes.

TECTONICS  Diverging boundaries form mid-ocean ridges as plates spread apart.  Converging boundaries can form mountains and volcanoes as plates come together.

TECTONICS  Hot spot is an area where material form deep with the mantle raises and then melts, forming magma.

WHERE ARE VOLCANOES? Most volcanoes are found on plate boundaries like the Ring of Fire. Volcanoes can also be found above a hot spots like Hawaii.

MAGMA/LAVA Viscosity – the resistance of a liquid to flowing. Honey is more viscous than water or has a higher viscosity than water.

MAGMA/LAVA  Temperature contributes to viscosity. The hotter the magma is, the lower its viscosity and the more rapid it flows.  Silica Content also contributes to viscosity. The more silica magma contains, the higher its viscosity and the slower it flows.

MAGMA/LAVA  Which type of magma will have a higher viscosity, Basalt- Forming or Rhyolite- Forming?  Rhyolite-Forming

TYPES OF LAVA Pahoehoe (pah-hoh ee hoh ee) Low Viscosity Aa (ah ah) High Viscosity

PARTS OF A VOLCANO

TYPES OF VOLCANOES  Shield Volcano  Cinder Cone Volcano  Composite Volcano  Caldera

SHIELD VOLCANO  Lava flow gradually builds a wide, gently sloping mountain.

SHIELD VOLCANOES

CINDER CONE VOLCANO  Ash, cinder, and bombs build up around the vent in a steep, cone- shaped hill or small mountain.

CINDER CONE VOLCANOES

COMPOSITE VOLCANO  Tall, cone- shaped mountains in which layers of lava alternate with layers of ash.

COMPOSITE VOLCANOES

CALDERA  The huge hole left by the collapse of a volcanic mountain.

CALDERAS

CALDERA: YELLOWSTONE

CALDARA: SANTORINI

ERUPTION IN PAPA NEW GUINEA

Start at 2:10

NATION GEOGRAPHIC