Volcanoes Flashcards
Learn everything by 1/31 😭
What is a volcano?
“An opening in Earth’s crust that erupts gases, ash, and lava”
How do volcanic mountains form?
They form from layers of ash, lava, etc.
What is the world’s most active volcano?
Mt. Kilauea
What are the 3 places where volcanoes can form?
Convergent plate boundaries, divergent plate boundaries, and hot spots
What is one of the most volcanically active areas in the world?
Iceland because it is located on the mid-ocean ridge and hot spots/mantle plumes
What is a hotspot/mantle plume?
An area underneath Earth’s crust where the magma is unusually hot
What can falling volcanic ash cause?
It can cause buildings to collapse, roads to be blocked, lung disease to people and animals, and generally a lot of destruction
What are pyroclastic flows?
When “super-hot volcanic ash, cinders, bombs, and other debris rush down the side of the volcano”. They travel at 100-150 mph and can reach temperatures such as 1500 F
What are pyroclastic flows made of?
Volcanic ash, cinders, debris, and bombs (the volcano kind)
What happens when gases are released from a volcano?
If water vapor escapes, then nothing harmful happens, but if another gas (lex. sulfur dioxide) escapes, it can lead to acid rain, global cooling, ozone destruction, choking rivers (stop flowing), and clog plant pores (kills the plants)
Which kinds of gases cause acid rain?
Sulfurous gases (sulfur dioxide, nitrogen oxide)
Which kinds of gases cause global cooling?
Sulfur dioxide
Which kinds of gases cause ozone destruction?
Sulfur dioxide
What are the cracks in which volcanic gas escapes from called?
Fumaroles
How are volcanoes formed?
Magma from underneath the crust rises and erupts. It then hardens to form a volcano
Why does magma rise when a volcano is formed?
The magma that forms a volcano is made from melted rocks, so it is less dense which causes it to rise
What is a crater?
“[a] steep-walled depression around a vent”
What is a volcanic vent?
“[an] opening in Earth’s crust through which magma is released.”
What is magma?
“molten rock below the Earth’s surface”
What is lava?
“molten rock flowing on the Earth’s surface”
How are volcanoes formed at a divergent plate boundary?
When the plates move apart and magma/lava rises, it hardens and builds up on the seafloor
What are rift volcanoes?
Volcanoes formed at a divergent plate boundary
How are volcanoes formed at a convergent plate boundary?
When the plates collide, the denser plate sinks underneath the less dense plate. This causes the magma to rise and form a volcano
Which plate boundary volcano has a violent eruption?
Convergent volcanoes
Which plate boundary volcano has a quiet eruption?
Divergent boundaries (rift volcanoes)
Why do hot spot volcanic islands move?
They move because the plate moves (ex. Hawaiian Islands)
What are the requirements to be considered an active volcano?
The volcano must have erupted in the last few thousand years
How many active volcanoes are there today?
About 1,500
How many volcanoes erupt each year that were thought to be dormant/extinct?
2-3 volcanoes
How do scientists predict when a volcano will erupt?
They monitor the shape of the volcano, changes in the composition of gases, and changes in the pattern and intensity of earthquakes
Where is the US ranked in the list of the most historically active volcanoes?
It is ranked in 3rd place, behind Japan (2nd), and Indonesia (1st)
Where are most of the active volcanoes in the US located?
The Hawaiian Islands, Aleutian Islands, Alaska Peninsula, and the Cascade Range of the Pacific Northwest
Which two factors control eruptions?
The amount of water vapor and gases and how much silica there is in the magma
What causes a buildup of pressure in a volcano before an eruption?
Surrounding rock layers, magma, and trapped gases
What happens when the magma rises before an eruption?
As the magma rises, the pressure in the volcano decreases, and the water turns into steam, which can “propel the eruption”. Once the gas (usually water vapor and carbon dioxide) escapes, it can cause an explosive eruption.
What is wet magma?
“Magma that has a lot of water vapor (GAS) at some convergent boundaries & can cause explosive eruptions when the oceanic plate slides another plate.”
What does it mean when magma/lava has high silica content?
It is thick and not very flowy
What does it mean when magma/lava has low silica content?
It is very runny and thin
What does it mean when magma/lava has a lot of gas content (water vapor)?
It means there is more pressure, therefore, the eruption is more explosive
What does it mean when magma/lava has a little gas content (water vapor)?
It means there is less pressure, therefore, the eruption is less explosive
What kind of silica content does basaltic magma have?
It has a low silica content, which means the it flows more easily.
What kind of eruption results from basaltic magma? (quiet or explosive)
Since the silica content in basaltic magma is low, gases are able to escape more easily, which makes the explosion less explosive (AKA quiet eruption)
What kind of gas content (water vapor) does basaltic magma have?
It has a low gas content
What are the two lava flows that quiet eruptions have on land?
Pahoehoe and aa
What does a pahoehoe lava flow look like?
Rope-like flow, moves easily (Yummy stereotypical lava flow super satisfying 10/10)
What does an aa lava flow look like?
Stiff, rough, crumbly flow (if you can even call it that) Looks like cookie crumbs falling from a volcano
What are lava fountains?
“Trapped gases in basaltic magma that can easily escape.”
What is lava that flows out through cracks of the ocean floor called?
Pillow lava
What is pillow lava?
Basaltic lava that flows underwater
What type of magma is usually associated with quiet eruptions?
Basaltic magma
What type of magma is usually associated with violent eruptions?
Rhyolitic (granitic) magma and (I think) andesitic magma
Which magma type produces the most violent eruptions?
Rhyolitic (granitic) magma (from a cinder cone volcano)
Why does rhyolitic (granitic) magma produce the most violent eruptions?
It has a high silica content (high viscosity) and a high gas content. This means that there is more pressure built up in the volcano, and the more pressure there is, the more violent the eruption.
Why do granitic and andesitic volcanoes have the most violent eruptions?
As well as having magma with a high gas and silica content, those volcanoes are found on convergent plate boundaries (ocean-ocean or continent-ocean), which cause more violent eruptions
Why do convergent plate boundaries produce violent eruptions?
This is because as the magma rises, it melts the crust, which has silica. This causes the magma to absorb high amounts of silica, which lead to more violent eruptions.
What colors are associated with basalt/basaltic magma?
Darker colors (ex. black)
What colors are associated with andesite/andesitic magma?
Both dark and light colors (mixture of the two)
What colors are associated with rhyolite/rhyolitic magma?
Lighter colors (ex. pink, white, etc.)
How does the amount of silica affect the color of a rock?
The more silica it has the lighter its color
What is one example of a felsic rock?
Granite
What is one example of an intermediate rock?
Diorite
What is one example of a mafic rock?
Gabbro
Where does basaltic magma come from?
The upper mantle
What is the viscosity of basaltic magma (high or low)?
Low
What is the amount of gas/gas content in basaltic magma?
1-2% (low [taper fade 🤨])
What is the amount of silica/silica content in basaltic magma?
50% (low taper fade)
What is the explosiveness of basaltic magma?
Low/least explosive
Where is basaltic magma located?
The oceanic and continental crust
Where does andesitic magma come from?
The oceanic crust and oceanic sediments
What is the viscosity of andesitic magma (high or low)?
Intermediate (60%)
What is the amount of gas/gas content in andesitic magma?
3-4% (intermediate)
What is the amount of silica/silica content in andesitic magma?
60% (intermediate)
What is the explosiveness of andesitic magma?
Intermediate (has both quiet and explosive eruptions)
Where is andesitic magma located?
Continental margins associated with subduction zones
Where is rhyolitic magma found?
The Continental crust
What is the viscosity of rhyolitic magma (high or low)?
High
What is the amount of gas/gas content in rhyolitic magma?
4-6% (high)
What is the amount of silica/silica content in rhyolitic magma?
70% (high)
What is the explosiveness of rhyolitic magma?
Most explosive
Where is rhyolitic magma located?
The Continental crust
What kind(s) of magma do composite/stratovolcanoes have?
Basaltic, Andesitic, and Granitic (Rhyolitic) magma
How much gas do composite/stratovolcanoes have?
Intermediate amount
What kinds of eruptions do composite/stratovolcanoes have?
Quiet and explosive
What are composite/stratovolcano eruptions made of?
Lava and tephra
Where are composite/stratovolcanoes found?
Convergent plate boundaries (ocean-continent)
What kind(s) of magma do cinder cone volcanoes have?
Andesitic and Granitic (rhyolitic) magma
How much gas do cinder cone volcanoes have?
A high amount
What kinds of eruptions do cinder cone volcanoes have?
Violent eruptions
What is the shape of a composite/stratovolcano like?
Steep, tightly packed (stereotypical volcano shape)
What is the shape of a cinder cone volcano like?
Steep sided but loosely packed (shorter and fatter composite volcano)
What are cinder cone volcano eruptions made of?
Tephra
Where are cinder cone volcanoes found?
Convergent plate boundaries (ocean-ocean)
What kind(s) of magma do shield volcanoes have?
Basaltic magma
How much gas do shield volcanoes have?
Low amounts
What kind of eruptions do shield volcanoes have?
Quiet
What do shield volcanoes look like?
Broad, with gently sloping sides (a mess)
What are shield volcano eruptions made of?
Solidified lava tightly packed
Where are shield volcanoes found?
On divergent plate boundaries or hot spots
What are the three types of volcanoes?
Composite/stratovolcano, cinder cone, and shield
What does the Volcanic Explosivity Index measure?
It measures the magnitude and intensity of eruptions. It goes from the numbers 0 (least) to 8 (greatest)
What is tephra?
“Bits of rock or solidified lava dropped from the air, cools & hardens; varies in size from volcanic ash, to cinders, to larger rocks (bombs & blocks)”
What are supervolcanoes?
Volcanoes that can produce a MASSIVE (😏) eruption than can cover over 240 cubic miles.
What are some examples of supervolcanoes?
Yellowstone and Long Valley (both in the US)
What are batholiths?
“[The] largest, intrusive igneous rock feature that was the central magma chamber.”
How are batholiths formed?
“Magma cools & crystallizes from beneath the Earth’s surface, but can be exposed at the surface due to weathering & erosion. Both breaks down Earth’s surface & exposes intrusive igneous features which becomes mountains, hills & other unique surface features.”
How large can batholiths be?
Hundreds of kilometers thick and wide
What is one example of a batholith?
Large granite domes in Yosemite National Park
What is a dike?
“Hardened magma that enters a vertical crack and cuts across rock layers.”
What is a sill?
“Magma that hardens between parallel rock layers.”
How are dikes and sills formed?
Magma squeezes in between the cracks of rocks and hardens (underground)
What is a volcanic neck?
“When a volcano stops erupting, magma hardens inside the vent. Weathering & erosion wear away the volcano’s sides because the cone is softer than the interior rock. The remaining interior core is called the volcanic neck.”
What is a 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 called a caldera.”
What is one example of a volcanic neck?
Ship Rock in New Mexico
What is one example of a caldera?
Kilauea Crater in Hawaii
What are eruption columns and clouds made of?
It is made up of solid particles (dust)
Why are eruption columns and clouds dangerous?
They can grow very quickly and very high. They can be dangerous to planes flying through them, collapse buildings, damage, crops, and damage electricity and machinery.
When do volcanoes emit gases?
All the time (even when the volcano is not erupting)
What are fumaroles?
Cracks in the ground where gases from a volcano escape from
What are lava domes?
Irregular mounds at the top of a volcano formed by viscous lava with a high concentration of silica
Which type(s) of lava cause lava domes?
Andesitic and Granitic (rhyolitic) lava
What are pyroclastic flows?
When the substances inside the volcano (ash, rock fragments, gas) flow down the volcano at intense speeds and high temperatures.
What are pyroclastic surges?
“Low density pyroclastic flows [that] can easily overflow ridges”
What are volcanic landslides?
Volcanic landslides are just like regular landslides except they occur on volcanoes and with volcanic material (rock fragments, debris, etc.)
Where do volcanic landslides occur?
They occur on steep sided volcanoes
What triggers a volcanic landslide?
It can be triggered by eruptions, heavy rain, earthquakes, and even just small movements of loose debris
What are lahars?
Mudslides made up of volcanic materials. They usually move at speeds 20-40 mph, but can be up to 50 mph. They are one of the deadliest volcanic hazards because they can occur even when a volcano is not erupting. They occur on snow/ice capped volcanoes.
What is the order of the Hawaiian Islands? (oldest to youngest)
Kauai, Oahu, Molokai, Maui, Hawaii
Ex. of shield volcano
Mt kilauea
ex. of composite volcano
Mt fuego
ex. of cinder cone volcano
pu’u pua’i
