Transcript Volcanic Eruptions

Volcanic Eruptions
Ms. Pilcher
Vocabulary
• Mafic lava- dark in color and is rich in
magnesium and iron.
• Felsic lava- lighter in color when cools,
high in silica.
• Pahoehoe- (puh-HOY-hoy) wrinkles that
are formed when lava cools rapidly.
• Aa- (AH-ah) refers to the sharp, blocky
texture of volcanic rock.
Vocabulary
• Pillow lava- round blobs of lava that
separate and cool underwater.
• Pyroclastic material- particles of lava
that fly into the air when eruption occurs.
• Volcanic ash- Particles less than 2mm
• Volcanic dust- Particles less than .25mm
• Lapilli- Particles less than 64 mm
Vocabulary
• Pillow lava- round blobs of lava that
separate and cool underwater.
• Pyroclastic material- particles of lava
that fly into the air when eruption occurs.
• Volcanic ash- Particles less than 2mm
• Volcanic dust- Particles less than .25mm
• Lapilli- Particles less than 64 mm
Vocabulary
• Volcanic bombs- clot of lava that spins through
the air and cools.
• Volcanic block- largest pyroclastic particle that
blast from the fissure or vent.
• Shield Volcano- covers a wide area and
generally result from lava eruptions.
• Cinder Cone- formed from explosive eruption.
• Composite Volcano- results from altering
layers of pyroclastic material and lava.
Vocabulary
• Stratovalconoes- also known as
composite volcanoes, highest volcanic
mountains.
• Crater- funnel shape around the vent of
the volcano.
• Caldera- basin in the crater that is created
when slippage occurs.
Vocabulary
• Stratovalconoes- also known as
composite volcanoes, highest volcanic
mountains.
• Crater- funnel shape around the vent of
the volcano.
• Caldera- basin in the crater that is created
when slippage occurs.
Volcanic Eruptions
• The lava that erupts from volcanoes allows
us to determine firsthand the material that
emerges from the mantle.
• Scientist has discovered that there are two
general types of lava.
– Mefic lava
– Felsic lava
Mafic Lava
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Dark in color when hardens.
Rich in Magnesium and Iron.
Forms much of the ocean crust.
When crust cools rapidly, surface
will form a crust.
Felsic Lava
• Lighter in color when
hardens
• Common in
continental crust
• Contains much silica,
with lesser amounts of
iron and Magnesium
Rock Formations
• When mafic lava cools and
forms wrinkles there called
pahoehoe (puh-HOY-hoy)
• Can break into jagged chunks
to form aa (Ah-ah)
• When lava flows into the ocean
and cools rapidly, it often
separates and forms pillow lava.
Kinds of Eruptions
• The kind of lava that reaches the surface
determines the force the volcano will
erupt.
• Lava that contains large amounts of
trapped gases produces a more explosive
eruption of lava.
Oceanic Volcanoes
• Usually produced by mafic lava.
• Mafic lava is very hot and thin, and flows
like almost as easy as water.
• Gases escape easier from mafic lava, so
erupts are usually quiet.
• Will flow from the opening like a red hot
river.
Continental Volcanoes
• Most commonly comprised of felsic lava.
• Tends to be cooler and thicker.
• Contains large amounts of trapped gases,
mostly water vapor and carbon dioxide.
• When fissure or vent opens, gases escape
explosively sending molten particles
shooting into the air.
Volcanic Rock Fragments
• Felsic lava explode throwing pyroclastic
material into the air.
• Formed when lava cools too fast or is
sprayed into the air and solidifies.
– Volcanic ash
– Volcanic dust
– Lapilli (luh-PIL-ie)
– Volcanic bombs
– Volcanic blocks
Volcanic Rock Fragments
• Volcanic ash
– Particles less than 2mm
• Volcanic dust
– Particles less than .25 mm
Volcanic Rock Fragments
• Lapilli
– Particles less than 64mm
• Volcanic bomb
– Round or spindle shape
Volcanic Rock Fragments
• Volcanic Blocks
– Largest pyroclastic material, can be as big as
a house!
Volcanic Features
• Volcanic activity produces a variety of
characteristic features on the earth.
• The lava and pyroclatic material ejected during
eruption can build up around the vent.
• These piles are known as volcanic cones; they are
classified into three different types.
– Shield Volcano
– Cinder Cones
– Composite Volcano
Volcanic Features
• Volcanic activity produces a variety of
characteristic features on the earth.
• The lava and pyroclatic material ejected during
eruption can build up around the vent.
• These piles are known as volcanic cones; they are
classified into three different types.
– Shield Volcano
– Cinder Cones
– Composite Volcano
Shield Volcano
• Covers a wide area
• Generally results from lava eruption
• Layers of hot mafic lava flow out around
the vent, harden, and slowly build up to
form a cone.
• The Hawaiian Island
are a chain of
shield volcanoes.
Cinder Cone
• Made up of solid fragments ejected from
the volcano.
• Most cinder cones have very steep slopes,
often close to 40 degrees.
• Rarely more than a few hundred meters
high.
Composite Volcano
• Many volcanoes have both quiet and
explosive eruptions.
• Composite volcanoes are formed as a
result of alternating layers of lava and
pyroclastic material.
• Also known as stratovalcanoes
Craters/ Calderas
• A creater is a funnel-shaped pit at the top
of the volcanic vent .
• Formed when material is blown out of the
volcano by explotion.
• Calderas are formed when slippage or
sinking occurs in the crater.
Predicting Volcanic Eruptions
• Volcanic eruptions can be one of earth’s
most destructive natural phenomena.
• Scientist are still making progress toward
increase there abilities in predicting
volcanic activity.
• Use instruments much like the one they
use with earthquake prediction.
Predicting Volcanic Eruptions
• Things they look for:
– Temperature changes within the rock
– Fracturing of rocks from pressure build-up
– Increase in # earthquake around volcano
– Increase is strength of earthquakes
– Bulging surface
– Change in gases given off by the volcano in
the area