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 volcanoes

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.)