Download Chapter 5 lesson 2

Lesson 5.2: Volcanic Eruptions Study Guide
Vocabulary
magma
chamber
pipe
vent
lava flow
crater
silica
Study Guide
the pocket beneath a volcano where magma collects
a long tube through which magma moves from the magma chamber to Earth’s surface
the opening through which molten rock and gas leave a volcano
the area covered by lava as it pours out of a volcano’s vent
a bowl shaped area that forms around a volcano’s central opening
a material found in magma that is formed from the elements oxygen and silicon; the primary
substance of Earth’s crust and mantle
pyroclastic the flow of ash, cinders, bombs, and gases down the side of a volcano during an explosive eruption
flow
dormant
not currently active, but able to become active in the future
extinct
no longer active and unlikely to erupt again
Key Idea: Volcanoes are made up of a group of parts that work together to move magma to the surface.
Key Idea: Volcanoes can be classified as active, dormant or extinct.
Active
Dormant
 Is erupting or is showing
 Is not currently active, but is
signs that it may soon
expected to become active in
the future (“sleeping volcano”)
Extinct
 Not expected to erupt again
(“dead volcano”)
 Ex: Hot spot volcanoes may
become extinct after they drift
away from the hot spot
Lesson 5.2: Volcanic Eruptions Study Guide
Study Guide
Key Idea: Eruptions can be quiet or explosive.
**Partly depends on silica content of magma
Quiet Eruptions
Explosive Eruptions
 Magma is HOT
 Magma is HIGH in silica
 Magma is LOW in silica
 Magma is thick and sticky
 Lava and gases flow and bubble out gently
Quiet eruptions can produce different lava and rock.
Pahoehoe
Aa
 forms from fast-running  forms from slow-moving
lava that is thin and
lava that is cooler and
runny
thicker
 surface looks like solid,  surface is rough and
rope-like coils
jagged
Key Idea: Both quiet and explosive volcanoes are hazardous.
Quiet Eruptions
Explosive Eruptions
 Lava flows from vents, setting fire to, and
 Pryoclastic flow-cloud of hot gases, ash,
burying anything in its path
cinders, and bombs move quickly down the
volcano
 Covers large areas with layer of lava
 Can cause landslides
Key Idea: Geologists can monitor the area around a volcano to observe warning signs that it may erupt.
 Notice changes in elevation caused by magma moving underground
 Monitor gases escaping from the volcano
 Detect small nearby earthquakes
 Record rising temperatures in underground water