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Volcanoes Test 5/5

Volcano A weak spot in the crust where molten material, or magma, comes to the surface
Magma a molten mixture of rock forming subtances, gases, and water from the mantle
Lava Liquid magma that reaches the surface; also the rock formed when liquid lava hardens
Ring of Fire A major belt of volcanoes that rims the Pacific Ocean
Island arc A string of islands formed by the volcanoes along a deep- ocean trench
Hot spot An area where material from deep within the mantle rises and then melts, forming magma
Where do volcanic belts form? Along the boundaries of Earth's plate
Where do volcanoes form and when? Above a hot spot when magma erupts through the crust and reaches the surface
Element A substance that cannot be broken down into other substances
Viscosity The resistance of a liquid to flowing
Compound A substance made of two or more elements that have been chemically combined
Silica The compound that is made up of particles of the elements oxygen and silicon
Physical property Any characteristic of a substance that can be observed or measured without changing the composition of the substance
Chemical property Any property that produces a change in the composition of matter
Pahoehoe Fast- moving hot lava that has low viscosity
Aa Lava that is cooler and slower moving
Why do some liquids flow more easily than others? Liquids differ in viscosity
What does the viscosity of magma depend on? Its silica content and temperature
What has a particular set of physical and chemical properties? Substances. These properties can be used to identify a substance or to predict how it will behave
Physical or Chemical? Density Physical
Physical or Chemical? Boiling Point Chemical
Physical or Chemical? Ability to burn Chemical
Physical or Chemical? Ability to react with other substances Chemical
Physical or Chemical? Hardness Physical
Physical or Chemical? Magnetic quality Chemical
Magma chamber The pocket beneath a volcano where magma collects
Pipe A long tube through which magma moves from the magma chamber to Earth's surface
Vent The opening through which molten rock and gas leave a volcano
Lava flow The area covered by lava as it pours out of a vent
Crater A bowl shaped area that may form at the top of a volcano around the central vent
Pyroclastic flow The expulsion of ash, cinders, bombs, and gases during an explosive volcanic eruption
Dormant Describes a volcano that is not currently active, but that may become active in the future
Extinct Describes a volcano that is no longer active and is unlikely to erupt again
What happens when a volcano erupts? The force of the expanding gases pushes magma from the magma chamber through the pipe until it flows or explodes out of the vent
How do geologists classify volcanic eruptions? Quiet or explosive
What terms do geologists use to describe a volcano's stage of activity? Active, dormant, or extinct
Why does magma in the mantle rise through the crust above it? The crust is less dense, the pressure from the gasses in the magma chamber, comes up from the weakest spot on the crust
As magma rises toward the surface, what happens to the gases in it? Why? The dissolved gases begin to expand, forming bubbles and exploding
Contrast the viscosity of magma in quiet and explosive eruptions Quiet eruptions: Low viscosity, low silica, high temp Explosive eruption: High viscosity, high silica, low temp
How does an explosive eruption produce a pyroclastic flow? Breaks lava into fragments that cool and harden into pieces of different sizes. Mixture of ash, cinders, and bombs
Describe the stages of volcanic activity Active, dormant, extinct
Shield volcano A wide, gently sloping mountain made of layers of lava and formed by quiet eruptions
Cinder cone volcano A steep, cone- shaped hill or small mountain made of volcanic ash, cinders, and bombs piled up around a volcano's opening
Caldera The large hole at the top of a volcano formed when the roof of a volcano's magma chamber collapses
Composite volcano A tall cone-shaped mountain in which layers of lava alternate with layers of ash and other volcanic materials
Volcanic neck A deposit of hardened magma in a volcano's pipe
Batholiths A mass of rock formed when a large body of magma cools inside the crust
Dike A slab of volcanic rock formed when magma forces itself across rock layers
Sill A slab of volcanic rock formed when magma squeezes between layers of rock
Geothermal activity The heating of underground water by magma
Geyser A fountain of water an steam that builds up pressure underground and erupts at regular intervals
What do volcanic eruptions create? Land forms made of lava, ash, and other materials. These land forms include shield, cinder cone, composite volcanoes, and lava plateaus
What features are formed by magma? Volcano necks, dikes, sills, batholiths and dome mountains
What are two types of geothermal activity and where are they found? Hot springs and geysers are often found in areas of present or past volcanic activity
Name each type of volcano and how is each formed? Shield: Quiet eruption, lava flows build up a sloping mt. Cinder Cone: Explosive eruption, ash, cinders, and bombs build up around the vent in a hill Composite: Quiet & Explosive eruption, lava flow then ash, cinders, and bombs (alternating)
How does a lava plateau form? When floods of lava flow with low viscosity are on top of earlier floods
What happens to create a caldera? An eruption has to empty the main vent and the magma chamber and the mountain collapses inward
Why is volcano soil so fertile? It contains nitrogen, potassium, and phosphorus
What are two uses of geothermal energy? Heating homes and electricity
Created by: jazzyylyy