Materials
Magma that reaches the Earth's surface.
Lava
Depression found at the top of most volcanic cones.
Crater
A rapid, downhill movement of hot, solid, and volcanic particles suspended in steam.
Pyroclastic Flow
A volcano that emits lava and solid debris in alternating quiet but explosive eruptions.
Stratovolcanoes
A spring heated by magma that periodically ejects hot water and steam.
Geyser
A compound made of silicon and oxygen; determines the viscosity of lava.
Silica
An enlarged depression caused by an explosion or collapse of a volcanic cone.
Caldera
The internal energy of the Earth that is sometimes harnessed for man’s use.
Geothermal Energy
A volcano that emits mostly cinders, ashes, and bombs.
Cinder Cones
The layer of the Earth where the geothermal gradient is the highest.
Lithosphere
Rocks that are related to volcanic processes and make up all volcanoes.
Expansive, thick layers of igneous rocks presumably formed by magma seeping through the ground.
Flood Basalts
A scale that geologists use to classify the destructiveness of a volcanic eruption.
A volcano that has no historical record of eruption, seismic indications of activity, and is heavily eroded.
Extinct Volcanoes
True or False: The VEI rates volcano activity only on the basis of the volume of rock discharged during an eruption.
False
Tiny, angular glass fragments that are emitted by volcanoes.
Ash
Vertical, wall-like intrusions that work their way into rock layers.
Dikes
Secular geologists believe that most of the Earth’s internal heat comes from this process.
A volcano that emits mostly lava in quiet eruptions; the largest volcano type.
Shield Volcanoes
Pools of water caused when hot groundwater seeps through the ground; often associated with mineral terraces.
Hot Springs
Streamlined masses of ejected lava that have solidified in flight.
Bomb
Horizontal intrusions that force themselves between rock layers and are supplied by dikes.
Sills
Lahars
According to the USGS, volcanoes that have not erupted in history, but are not significantly eroded are called this.
Dormant Volcanoes
Batholiths and laccoliths are types of these, large bodies of igneous rock formed when magma cools below the surface.
Plutons