Geology Reference
In-Depth Information
Lava is not the only material that erupts from volcanoes. Many volcanic erup-
tions also release gases, ash
(tephra),
and fragmented rock particles
(pyroclastics)
into the air. These erupted materials build up around the opening of the volcano
and create volcanoes of different shapes and sizes.
Volcanoes have certain features, which I describe here and illustrate in Figure 7-1:
Figure 7-1:
Features of a vol-
cano.
Magma chamber:
Deep beneath the surface of the earth (about 60 kilometers or 37
miles), magma is created and held in the magma chamber until enough pressure
builds to push it toward the surface.
Pipe:
Magma moves from the magma chamber up to the surface through a
pipe.
Vent:
Magma exits the pipe onto the surface at a
vent.
Vents that erupt only gases
(no lava) are called
fumaroles.
Crater:
The vent usually opens into the
crater,
which is a depression created at the
top of a volcano from the collapse of surface materials inward when the magma
chamber is emptied after an eruption.
Caldera:
A
caldera
is a very large crater formed when the top of an entire volcanic
mountain collapses inward.
