Chapter 5 Volcano Test Flashcards
Convergent Plate Boundaries
Clashing together (subduction zones)
Divergent Plate Boundaries
Pulling Apart (Mid-ocean ridges)
Hot Spots
Where mantle plumes cut the lithosphere
What are signs that scientists look for when predicting volcanic eruptions?
Earthquake activity - magma flow increases seismicity.
Heat flow - magma causes volcanoes to “heat up.”
Changes in shape - magma causes expansion.
Emission increases - changes in gas mix and volume.
What happened to the surrounding area around Lake Nyos in Cameroon as a result of the eruption there?
belched CO2 during overturn. Moved down the valleys as a heavier-than-air underflow.
What is the greatest hazard to humans that is associated with volcanos?
Pyroclastic Debris
Iceland is an example of a hot spot located over what?
Mid-Atlantic Ridge
Mafic Lava Characteristics
very hot, low silica, and low viscosity
Felsic Lava Characteristics
not as hot, high in silica and volatiles, and have a high viscosity.
Stratovolcano Volcano
also called composite volcanoes. Large, cone-shaped volcanoes with steeper slopes. Made of alternating layers of lava, tephra, and debris. Examples include Mount Fuji, Mount Rainier, and Mount Vesuvius.
Cinder Cone Volavno
( AKA: Scoria cones): Conical piles of tephra; the smallest type of volcano. Built of ejected lapilli and blocks piled up at a vent. Often symmetrical, with a deep summit crater. Typically from a single eruption event.
Shield Volcano
Broad, slightly dome-shaped (like an inverted shield). Constructed by lateral flow of low-viscosity basaltic lava. Have a low slope and cover large geographic areas. Mauna Loa in Hawaii is a perfect example.
Explain what a caldera is. Know how are they formed?
A caldera is a large crater-shaped basin that forms when the top of a volcano collapses.
Lahar
water-rich debris flow of ash and blocks. mudflows result when water moves ash.
Pillow basalt (lavas)
round blobs of basalt cooled in water
Tuff
lithified ash, may or may not contain lapilli
Pele’s Hair
thin glass strands
Pele’s Tears
frozen droplets
A’a’
Hawaiian word describing basalt that solidifies
with jagged, sharp, angular textures. Forms when hot basalt cools & thickens.
Pahoehoe
Hawaiian word describing basalt with a glassy or ropy texture. Forms when extremely hot basalt forms a skin.
What is tephra? Be able to identify examples.
deposits of pyroclastic debris of any size. Examples are Ash, Lapilli, Air-fall tuff, and Ignimbrite.
What are Volcanic Bombs and how are they formed?
A small lump of magma that is thrown up into the air during an explosive volcanic eruption as molten rock and then cools into a solid fragment before it reaches the ground.
What is volcanic debris? List some examples.
wetted debris that moves downhill. Examples are gas, lava, and fragmented debris called tephra.
What are common volcanic gasses?
Water (H2O)
Carbon dioxide (CO2)
Sulfur dioxide (SO2)
Hydrogen sulfide (H2S)
Compare and contrast effusive and explosive eruptions
Effusive eruptions—An eruption dominated by the outpouring of lava onto the ground. Produce lava flows.
Explosive eruptions—blow up. Have high silica content. Lots of stuff gets erupted in the air. As a result, it changes the climent-adjasent to a subduction zone.
What eruption buried the town of Pompeii with pyroclastic debris in 79 A.D.?
the eruption of Mount Vesuvius
Dormant Volcanos
hasn’t erupted in hundreds to thousands of years
Active Volcanos
erupting, recently erupted or likely to erupt
Extinct Volcanos
not capable of erupting
Review the table that compares and contrasts Basaltic, Andesitic, and Rhyolitic Lava flows and their locations.
Basaltic Magma: Least (~50%) Silica Content. Least Gas Content. Least viscous. Rarely explosive. Highest Melting Temp. Located on Rifts, oceanic hot spots.
Andesitic Magma: Intermediate (~60%) Silica Content. Intermediate Gas Content. Intermediate Viscosity. Sometimes explosive. Intermediate Melting Temp. Located on Subduction boundaries.
Rhyolitic Magma: Most (~70%) Silica Content. Most Gas Content. Most viscous. Usually explosive. Lowest Melting Temp. Located on Continental hot spots.
Review large Igneous Provinces (LIP) - what type of lava are they typically formed from?
LIPs—unusually large outpourings of magma. Mostly mafic, include some felsic examples. Mostly mafic, include some felsic examples. Mantle plume first reaches the base of the lithosphere. Erupts huge volumes of mafic magma as flood basalts.
Know how volcanic eruptions can impact glocal temperatures - some even changing global climates for a period of time.
Ash and aerosols (tiny liquid droplets) are injected into the stratosphere, rapidly circling the globe. Particles remain in the stratosphere for months to years. This reflects solar radiation, causing atmospheric cooling.
