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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.)