EAPS 105 EXAM Q&A
What is the consequence of a planet or moon being hot? - Answer-Differentiation,
Magnetic Fields, Plate Tectonics, and Volcanism
what is the state (solid/liquid) of each layer in the Earth? - Answer-Crust - Solid
Mantle - Solid
Outer Core - Liquid
Inner Core - Solid
What is the difference between magma and lava? - Answer-both are melted rock, but
the distinction is that magma is below the surface while lava is above the surface
Which type of volcanism is observed on the other terrestrial planets? - Answer-hot
spots: mid ocean ridges and subduction zones require plate tectonics, which has not
been observed on other terrestrial planets
How much of the Earth's mantle is actually melted rock? - Answer-a very small
percentage and only at very specific places close to the surface
What 3 ways can you get hot rocks to melt? - Answer-1. increase temperature -
uncommon
2. decrease pressure (depressurized melting)- reduces the melting temperature of rocks
as they experience a decrease in pressure as they rise closer to the surface
3. add water to the mineralogy (hydration-induced melting) - changes the chemistry to
break up long silica chains to reduce the rocks melting temperature
What causes hot rocks to melt at subduction zones? - Answer-hydration-induced
melting, as water is drawn down as subduction occurs
What does the "Ring of Fire" refer to? - Answer-Subduction zone volcanism occurs
everywhere plates are subducted, causing a "ring of fire" around the pacific ocean
Why are there fewer active volcanoes in the U.S. southwest compared to the
northwest? - Answer-There is no active subduction zone in the southwestern U.S.
What causes hot rocks to melt at hotspots? - Answer-depressurized melting
Why do hotspots on Earth lead to hotspot tracks? - Answer-Hotspots stay at static
position on the earth, but plate tectonics lead to hotspot tracks (example: hawaiian
islands)
What is an effusive volcanic eruption? - Answer-if magma can flow to the surface
through a vent or crack without building up high pressure (low pressure eruption)
, Why does pressure in magma build as it rises to the surface? - Answer-dissolved gas in
the magma expands to form gas bubbles as the pressure decreases as the magma
rises; but as the gas bubbles take up more volume within the magma, the pressure
within the magma increases
What is volcanic ash? - Answer-conductive shards of volcanic glass
What does viscosity measure? - Answer-how easily a fluid flows
What kind of volcano does low viscosity magma lead to? - Answer-lead to broad,
shallow, sloped volcanoes (shield)
What is the tallest on earth, measured from base to peak? - Answer-Mauna Kea (on the
big island of hawaii)
How does a stratovolcano form? - Answer-midsize volcanoes that form as a result of
alternating pyroclastic flow and effusive lava flows
How does a cinder cone form? - Answer-build when Tephra (air cooled lava fragments)
are thrown out of a volcanic vent
What combination of magma viscosity and gas content is most likely to lead to explosive
eruptions? - Answer-high viscosity and high gas content
What factors control how much gas pressure builds below the surface? - Answer-1.
amount of magma
2. amount of dissolved gas
3. viscosity of magma - low viscosity magmas will flow through cracks to the surface,
while sticky magmas will resist flow and allow great pressure to build
What are the least to most powerful types of volcanic eruptions? - Answer-Hawaiian -
low volume, low pressure
Strombolian - bursting of large gas bubbles that form from one large collection of
volcanic explosivity; low volume, high pressure
Vulcanian - high volume, low pressure
Plinian - high volume, high pressure
Where do giant flood basalts originate from? - Answer-when hot spot mantle plumes
first protrude to the surface, they cause giant flood basalts (huge flows of over 1000 sq
km that occur in a relatively short amount of time)
Which planets are covered by flood basalts? - Answer-1. Mercury - it does not have
plate tectonics to shed heat, so it is covered in flood basalts
2. Venus - because venus does not have plate tectonics, it is also entirely covered with
flood basalts; these all occurred in a relatively short timespan about 500 million years
ago
What is the consequence of a planet or moon being hot? - Answer-Differentiation,
Magnetic Fields, Plate Tectonics, and Volcanism
what is the state (solid/liquid) of each layer in the Earth? - Answer-Crust - Solid
Mantle - Solid
Outer Core - Liquid
Inner Core - Solid
What is the difference between magma and lava? - Answer-both are melted rock, but
the distinction is that magma is below the surface while lava is above the surface
Which type of volcanism is observed on the other terrestrial planets? - Answer-hot
spots: mid ocean ridges and subduction zones require plate tectonics, which has not
been observed on other terrestrial planets
How much of the Earth's mantle is actually melted rock? - Answer-a very small
percentage and only at very specific places close to the surface
What 3 ways can you get hot rocks to melt? - Answer-1. increase temperature -
uncommon
2. decrease pressure (depressurized melting)- reduces the melting temperature of rocks
as they experience a decrease in pressure as they rise closer to the surface
3. add water to the mineralogy (hydration-induced melting) - changes the chemistry to
break up long silica chains to reduce the rocks melting temperature
What causes hot rocks to melt at subduction zones? - Answer-hydration-induced
melting, as water is drawn down as subduction occurs
What does the "Ring of Fire" refer to? - Answer-Subduction zone volcanism occurs
everywhere plates are subducted, causing a "ring of fire" around the pacific ocean
Why are there fewer active volcanoes in the U.S. southwest compared to the
northwest? - Answer-There is no active subduction zone in the southwestern U.S.
What causes hot rocks to melt at hotspots? - Answer-depressurized melting
Why do hotspots on Earth lead to hotspot tracks? - Answer-Hotspots stay at static
position on the earth, but plate tectonics lead to hotspot tracks (example: hawaiian
islands)
What is an effusive volcanic eruption? - Answer-if magma can flow to the surface
through a vent or crack without building up high pressure (low pressure eruption)
, Why does pressure in magma build as it rises to the surface? - Answer-dissolved gas in
the magma expands to form gas bubbles as the pressure decreases as the magma
rises; but as the gas bubbles take up more volume within the magma, the pressure
within the magma increases
What is volcanic ash? - Answer-conductive shards of volcanic glass
What does viscosity measure? - Answer-how easily a fluid flows
What kind of volcano does low viscosity magma lead to? - Answer-lead to broad,
shallow, sloped volcanoes (shield)
What is the tallest on earth, measured from base to peak? - Answer-Mauna Kea (on the
big island of hawaii)
How does a stratovolcano form? - Answer-midsize volcanoes that form as a result of
alternating pyroclastic flow and effusive lava flows
How does a cinder cone form? - Answer-build when Tephra (air cooled lava fragments)
are thrown out of a volcanic vent
What combination of magma viscosity and gas content is most likely to lead to explosive
eruptions? - Answer-high viscosity and high gas content
What factors control how much gas pressure builds below the surface? - Answer-1.
amount of magma
2. amount of dissolved gas
3. viscosity of magma - low viscosity magmas will flow through cracks to the surface,
while sticky magmas will resist flow and allow great pressure to build
What are the least to most powerful types of volcanic eruptions? - Answer-Hawaiian -
low volume, low pressure
Strombolian - bursting of large gas bubbles that form from one large collection of
volcanic explosivity; low volume, high pressure
Vulcanian - high volume, low pressure
Plinian - high volume, high pressure
Where do giant flood basalts originate from? - Answer-when hot spot mantle plumes
first protrude to the surface, they cause giant flood basalts (huge flows of over 1000 sq
km that occur in a relatively short amount of time)
Which planets are covered by flood basalts? - Answer-1. Mercury - it does not have
plate tectonics to shed heat, so it is covered in flood basalts
2. Venus - because venus does not have plate tectonics, it is also entirely covered with
flood basalts; these all occurred in a relatively short timespan about 500 million years
ago
