 Vent-
lava erupting through crack/ hole in
the crust
 Crater- bowl shaped depression at the top
of the volcano
 Caldera- up to 50km forms when part of
volcano collapses
 Tephra- rock fragments thrown into the air
 Pyroclastic flow- the flow of material down
the side of the volcano
 Lahar- mudflow with volcanic debris
 1. lava
erupts through a vent
 2.lava cools and hardens around vent
 3.slowly builds up walls of volcano
 Sizes vary
• Dust <2 mm
• Ash > dust, but < 2 mm in diameter
• Lapilli 2-64 mm (little stones in Italian)
• Tephra up to size of a small building
 May be blown up to 10km into the
air
 Pyroclastic may move down the volcano
up to 200km p/h
 Creates lahar when mixed with mud
 May exceed 700 C
 Forms
out of non explosion eruptions.
 Has broad slight slopes
 Build layer by layer by flowing lava
 Straight sides
 Quiet eruptions
Mauna Loa in Hawaii
 Formed
out of explosions and material
falling around vent
 Steep sides
 <1000 m high
 Contains large
amounts of silica,
water, and gas
 Small in
comparison
Lava Butte in Newberry National Volcanic Monument, Oregon
 Formed
layer upon layer of mostly
viscous magma
 Relative steep sides
 A volcano composed of both lava flows
and pyroclastic material.
 Very large
 Highly explosive
 Occur
due to plates moving into each
other
 Magma forced upward due to additional
material being subducted
 Ex. Pacific ring of fire
 Mostly
occur along ocean ridges
 Caused by plate separation forming new ocean
floor (through the process of seafloor
spreading)
 Ex. Mid Atlantic ridge
 Unusually
hot regions of the mantle near
the crust
 Will dissolve into the crust (lithosphere)
 May be formed by plumes of heat close to
the core