Transcript Volcanic Bombs

NON-EXPLOSIVE ERUPTIONS
• Non-explosive eruptions are the most
common type of eruptions.
• These eruptions produce relatively
calm flows of lava.
• Non-explosive eruptions produce
large amounts of lava.
EXPLOSIVE ERUPTIONS
• Explosive eruptions are much rarer than nonexplosive eruptions.
• Explosive eruptions are incredibly destructive
releasing clouds of hot debris, ash and gas
rapidly shooting out of the volcano.
• Instead of lava flow, explosive eruptions cause
molten rock to be blown into tiny particles that
harden in the air.
• An explosive eruption can also blast millions of
tons of lava and rock from a volcano.
Volcanic Fragments
• Volcanic Dust- less
that 0.25 mm in
diameter (flour)
• Volcanic Ash- more
than 0.25 less than 5
mm (rice)
• Volcanic Bombsfew cm to several
meters.
• Cinders- volcanic
bombs the size of golf
balls
What Erupts from a Volcano
Magma erupts as either lava or
pyroclastic material
• Lava- is liquid magma that flows from
a volcanic vent
• Pyroclastic material- forms when
magma is blasted into the air and
hardens.
Types of Pyroclastic Material
• Volcanic bombs- large blobs of magma that hardens in
the air.
• Lapilli- means “little stones” are pebble like bits of
magma that hardens before they hit the ground.
• Volcanic ash- forms when the gases in stiff magma
expand rapidly and the walls of the gas bubbles explode
into tiny glasslike slivers.
• Volcanic blocks- the largest pieces of pyroclastic material
which are pieces of solid rock erupted from volcanoes.
Pyroclastic Flows
• Pyroclastic flows are a dangerous type of
volcanic flow that produces an enormous
amount of hot ash, dust, and gases that
are ejected from a volcano.
• Pyroclastic flows can race downhill at
speeds of 200km/hr or faster. (faster than
hurricane winds)
• The temperature of pyroclastic flows can
exceed 700 degrees C.
Where Volcanoes Form
A large number of volcanoes lie directly
on tectonic plates boundaries. In fact, the
plate boundaries surrounding the Pacific
Ocean have so many volcanoes that the
area is called the ring of fire.
Ring of Fire
Zones
• There are 3 zones:
• Ring of Fire- Extends nearly all the way
around the edge of the Pacific Ocean
• Mediterranean Sea- Italy, Greece,
Turkey
• Iceland and Atlantic Ocean- Mid
Atlantic Ridge
Volcanic Terminology
Volcanic Landforms
• Crater- funnel shaped pit, or
depression at top of volcano
• Caldera- when a crater
becomes too large, it
collapses: also can form when
the top of a volcano collapses
or explodes
• Lava plateau- is a landform
that resulted from repeated
eruptions of lava spread over a
large area. Ex- Columbia River
Plateau
• Dormant- sleeping volcano
• Extinct- not known to have
erupted in modern history
• Active- Erupts fairly regularly
• Hot spots- Volcanically active
places on the Earth’s surface
that are far from plate
boundaries