How do volcanoes shape the

land?

Chapter 5: Lesson 3:

Openings in earth’s crust.

Volcanoes are located on certain places on earth’s surface.

(Found where tectonic plates meet)

A circle of volcanoes (Ring of fire) follows the boundaries of plates that meet along the

pacific ocean.

EruptionOutpouring of ash, gases, lava or a combination of these.

Magma chamber

Inside a volcano

Vent

Vent

Smoke and ashes

Crater

Lava

Crater(cup shaped depression)

Volcanoes erupt where one plate is pushed under another.

The hole that is formed when the chamber under the volcano is emptied

and the volcano collapses.

Caldera

1) Dike(Formed when magma hardens in vertical or nearly

vertical cracks)

Underground magma formations

2) Sill(Formed when magma hardens in horizontal layers

of rock)

3) Laccolith(A dome shape formed when magma is pushed into

a sill and doesn’t spread) When a laccolith is formed it may push the layers of rock above it.

4) Batholith(Huge, irregular shape deep in the earth’s crust)

Active volcanoes(Currently erupting or

recently erupted)

Types of volcanoes

Dormant volcanoes

(Does not erupt for some time)

Shield volcano

es

Cinder-cone

volcanoes

Composite

volcanoes

Extinct volcanoes(Stopped erupting)

1) Shield volcanoes

Built by thinner, fluid lava that spreads over a large area.

(Broad base and gently sloping sides)

2) Cinder-cone volcanoes

Formed by thick lava that is thrown high up in the air and fall as chunks or cinders.

(Form as cone shape with narrow base and steep sides)

3) Composite volcanoes

Built by layers of ash and cinders sandwiched between layers of hardened

lava.(Both sides of a composite volcano look the same)

Active volcano not on boundary

Hot spot (A stationary pool of magma)

The Hawaiian islands are form an island chain.The origin of the Hawaiian island volcanoes is the hot spot.

Island arc(Formed in areas where an ocean floor plate is pushed under another ocean

floor plate.)