Volcanoes Flashcards
Volcano
an opening in the earth that erupts gases, ash, and lava
Magma
molten rock below the Earth’s surface
Crater
steep-walled depression around a vent
Volcanic vent
Opening in Earth’s crust through which magma is released
Fumarole
A type of vent where steam, water vapor, sulfur dioxide, carbon dioxide, and hydrochloride acid are emitted
Lava
Molten rock above the earth’s surface
What can volcanic ash do?
Collapse buildings, block roads, cause lung disease in people and animals destroying everything in its path
Pyroclastic flows
Super hot volcanic ash, cinders, bombs, and other debris rush down the side of the volcano
Acid rain
Sulfurous gases mix with water vapor in the atmosphere
Where can volcanoes form?
Divergent & convergent plate boundary and hot spots
Divergent plate boundary volcanoes
Plates move apart as more lava flows and hardens, it builds up on the seafloor
Rift volcanoes
What divergent plate boundaries form. Can form islands
Convergent plate boundary volcanoes
2 plates move together & collide denser plate sinks or sub ducts into the mantle. violent.
Hot spot
Areas at the boundary between Earth’s mantle and core that are usually hot
Hot spot volcanoes
They form islands. temporary islands due to the moving plates.
Active volcano
Erupted within the last few thousand years
How many active volcanoes are there around the world today?
1,500
Where does the U.S rank in the number of volcanoes?
3rd
What are the two factors that control eruptions?
The amount of water vapor/gases and how much silica is present in the magma
Wet magma
Magma that has a lot of water vapor and can cause explosive eruptions
Silica
Thickness of magma
A lot of silica
Think, pasty
a little bit of silica
Thin, runny
A lot of gas (water)
High pressure, the more explosive
Little/no water
Low pressure, the less explosive
Basaltic magma
Low silica content, gases can easily escape. Quite and non explosive
Where does basaltic magma usually occur?
Hot spots and divergent plate boundaries
Pahoehoe
Quiet eruptions on land. Rope-like with smooth surface, flows well
aa
Quiet eruption on land. Lower temperature, stiff and rough surface
Lava fountains
Trapped gases in basaltic magma can escape easily
Pillow lava
Comes out of the cracks of the ocean floor. Basaltic lava that flow underwater
Rhyolitic magma
Greatest explosion because high silica, high viscosity, and high gas content
Basaltic magma source material
Upper magma
Andesitic magma source material
Oceanic crust and oceanic sediments
Rhyolitic magma source material
continental crust
Basaltic magma viscosity
low
Basaltic magma gas content
1-2%
Basaltic magma silica content
about 50%
Basaltic magma explosivness
least
Basaltic magma location
Both oceanic and continental crust
Andesitic magma viscosity
Indermediate
Andesitic magma gas content
3-4%
Andesitic magma silica content
About 60%
Andesitic magma explosiveness
Intermediate
Andesitic magma location
continental margins associated with subduction zones
Rhyolitic magma viscosity
high
Rhyolitic magma gas content
4-6%
Rhyolitic magma silica content
about 70%
Rhyolitic magma explosiveness
Greatest
Rhyolitic magma location
Continental crust
Composite/ stratovolcanoes magma
Basaltic/granitic/ andesitic magma
Composite/ stratovolcanoes eruptions
Quiet & violent
Composite/ stratovolcanoes composition
Tephra and lava
Composite/ stratovolcanoes plate boundary
convergent (ocean-continent)
Composite/ stratovolcanoes gas content
mid
Cindercone magma
Andesitic/ granitic magma
Cindercone gas content
High
Cindercone eruption
Violent
Cindercone composition
Tephra
Cindercone plate boundary
Convergent (ocean-ocean)
Tephra
Bits of rock or solidified lava dropped from the air, cools & hardens
Supervolcanoes
Volcanoes that had eruptions that covered more that 240 cubic miles
Volcanic Explosivity Index (VEI)
a scale that describes the size of explosive volcanic eruptions based on their magnitude and intensity
Batholith
Largest intrusive igneous rock feature that was the central magma chamber
Dike
Hardened magma that enters a vertical crack and cuts across rock layers
Sill
Magma that hardens between par
Volcanic neck
a column of solidified lava or igneous rock formed in a volcanic vent, especially when exposed by erosion.
Caldera
After an eruption, the top of a volcano can collapse. This produces a large depression of an old volcanic crater that can fill with water to form a lake
