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Earth and Space Ch. 18

Terms in this set (13)

Define Volcanism
the discharge of magma, hot fluids, and gases
. What are hot spots? Give an example of a string of volcanoes formed by a hot spot.
unusually hot regions of Earth's mantle where high-temperature plumes of magma rise to the surface. Hawaiian Islands are an example
What is the world's most active volcano?
Kilauea
define tephra
materials that erupt from a volcano and fall back to Earth
Which vocabulary word means resistance to flow?
viscosity
Describe a pyroclastic flow.
Type of lava flow that has rapidly moving clouds of tephra mixed with hot, suffocating gases, with internal temps of 700°C and lead to numerous deaths.
Describe the different types of volcanoes. Give examples of each type of volcano.
Shield: mountain with broad, gently sloping sides. Layers of lava accumulate during nonexplosive eruptions. Ex. Mauna Loa
Cinder cone: Eruptions eject tephra into air that falls back down around the vent. Small with steep sides, form near larger volcanoes. Ex. Lassen volcanic park
Composite: layered, hardened chunks of lava from violent eruptions alter with layers of lava that oozed down the side. Cone shaped with concave slopes. Pose greatest threat to humans. Ex. Mount St. Helens.
Describe the types of volcano formation.
Convergent: oceanic plate descends beneath continental forming magma which moves upward. This is how most land volcanoes formed.
Divergent: tectonic plates move apart and new ocean floor is produced as magma rises to fill the gap. usually nonexplosive.
Hot spots: unusually hot regions of Earth's mantle where high-temp plumes of lava rise to the surface.
Draw a volcano, include the terms crater, caldera, vent, conduit, magma chamber and define each term.
vent: lava exits the volcano here
conduit: tubelike structure where magma flows to the surface
crater: bowl shaped depression around the vent
caldera: large depression where a previous magma chamber emptied and the volcano collapsed magma chamber: where magma is held
Which factors determine the composition of magma?
magmas interact with overlying crust, temp, pressure, amounts of dissolved gases, and the amount of silica a magma contains.
Which types of gases are found in magma?
water vapor, CO2, sulfur dioxide, hydrogen sulfide
Describe why large explosive eruptions are dangerous for humans and the environment.
Tephra can disperse over many miles/most of the planet, ash can change the weather. Ex. sulfuric acid droplets and particles remained in the atmosphere for 2 years blocking sun's rays and lowering temps.
List and describe the types of magma.
basaltic- less than 50% silica. low viscosity, quiet, unreactive with continental crust, dissolved gases escape easily
andesitic: 50-60% silica comes from oceanic crust or oceanic sediments. intermediate viscosity and intermediate explosivity
rhyolitic- greater than 60% silica. Molten material rises and mixes with continental crust. High viscosity slows down its movement and large volume of gas makes it very explosive.
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