volcanic eruptions ms. pilcher. vocabulary mafic lava- dark in color and is rich in magnesium and...
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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• 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
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