Name
Definition
Lahar
A hot or cold mixture of water and
rock fragments flowing down the
slopes of a volcano or river valley
In a volcanic eruption, heat melts
snow and ice; water mixes with ash
and rock and forms a mud flow;
gravity pulls it downhill
Destruction of structures, buries
towns in mud; crops and electrical
grids are damaged
Fragments of volcanic rock and
lava blasted into the air and
carried upward by hot gases
Explosive volcanic eruption
Streams of molten rock that pour
from an erupting volcanic vent
Molten magma forces its way to the
surface and is erupted in a nonexplosive way or as lava fountains
Can travel 1000’s of km; air pollution
can affect air travel; respiratory
system; accumulation of ash
destroys crops, collapses roofs;
destroys aircraft engines
Fluid lava can extend tens of
kilometers; everything in the path of
the lava is destroyed.
Large masses of rock and soil that
fall, slide or flow rapidly under the
force of gravity
Rock material loosened by the force
of a volcanic eruption that slides
down the side of the volcano at a
very high velocity
Destroys everything in its path; may
open a volcanic vent and result in
an explosive eruption (such as Mt.
St. Helens)
High density mixtures of hot rock
fragments and hot volcanic gases
that move at high speed down
the sides of a volcano, generally
following valleys
A series of waves that can travel
up to 1000 km per hour across
open ocean
An explosive volcanic eruption
produces the dense mixture of hot
gases and rock fragments
Destroys and incinerates everything
in its path; moves at very high
speeds (up to 100 mph), so it can’t
be outrun
Caused by disturbances such as
earthquakes or volcanoes that
displace large volumes of water
Sudden inundation of coastlines,
resulting in flooding, destruction of
buildings, and sediment erosion and
deposition
Volcanic Gas
Gases that are dissolved in the
magma and released in an
eruption
As magma erupts and pressure is
released, dissolved gases come out of
solution
Expanding gases can cause
explosive eruption; gases can be
harmful (respiratory problems) and
can cause climate change
Earthquake
The energy released when two
blocks of the earth’s crust
suddenly slip past one another
Stress from forces beneath Earth’s
surface builds up until the rock breaks
and moves along a fault
Seismic waves move away from the
earthquake in every direction,
causing movement in the Earth’s
surface that can do significant
damage
(Tephra)
Ash fall
Lava flow
Landslide
Pyroclastic Flow
Tsunami
How does this event occur?
What are the hazards?