Chapter 6 – 1 Volcanoes and Plate Tectonics What is a Volcano?

A volcano is a weak spot in the Earth’s crust where LESS DENSE molten material or magma comes to the surface.

Magma at Earth’s surface is called LAVA.

Location of Volcanoes “Ring of Fire”

LOCATION OF VOLCANOES Formed by many volcanoes that rim the Pacific Ocean. Not the only volcanic belt on Earth.

AT DIVERGENT BOUNDARIRES Most volcanoes occur along divergent plate boundaries, (Mid- Ocean Ridge, Iceland) where convection currents push landmasses apart.

AT CONVERGENT BOUNDARIES Volcanoes are also found in subduction zones (convergent boundaries) along the edges of oceans.

HOT SPOT VOLCANOES Hot spot volcanoes are areas of land or ocean where magma melts through Earth’s crust. Hawaiian Islands, Yellowstone NP

6 – 3 Volcanic Landforms Volcanic Rock creates a variety of landforms from lava and ash.

SHIELD VOLCANOES Thin layers of lava pour out and build up and up on previous layers.

CINDER CONE VOLCANOES Steep, cone shaped hill or mountain composed of thick lava, cinders and ash .

COMPOSITE VOLCANOES Lava flows alternate with explosive eruptions forms tall cone shaped mountains of lava and ash.

LAVA PLATEAUS High level areas formed by thin, runny lava flows.

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

SOILS FROM LAVA AND ASH

LANDFORMS FROM MAGMA

A Volcanic Neck forms when magma hardens in a volcano’s pipe and the softer surrounding rock wears away.

Magma that forces itself across rock layers hardens into a dike.

Magma that squeezes between layers of rock forms a sill.

A batholith is a mass of magma that cools inside the crust.

A dome mountain forms when rising magma is blocked by horizontal layers of rock.