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AU / Geology / GEOL 1100 / What determines volcanic eruption?

What determines volcanic eruption?

What determines volcanic eruption?


School: Auburn University
Department: Geology
Professor: Hawkins
Term: Fall 2016
Tags: Geology, geology notes, volcanoes, and Hawkins
Cost: 25
Name: Geology notes on Volcanoes week 10-11
Description: These notes include information on volcanoes stressed in class, in the textbook and in the purple notebook. These notes include the types of eruptions, volcanoes and much more. The bold topics consist of important things to know.
Uploaded: 10/26/2016
4 Pages 55 Views 5 Unlocks


What determines volcanic eruption?

The United States

• The most visited sites

o Yellowstone national park

o Mount St. Helens

▪ Last eruption of the U.S.

???? May 18, 1980

Types of eruptions (change viscosity)

• Quite

o Non explosive, generally mafic lava

▪ Example: Hawaii volcanoes National park

• Explosive

o Deadly, intermediate and felsic lava, high viscosity

▪ Mount St. Helens

• How to determine what kind of eruption it is?

o The amount of silica found in the molten material that  the volcano is erupting

What do lava and magma have in common?

▪ High silica content (more felsic in nature) this  

makes the material very viscus and allows it to  

trap a large quantity of dissolved gasses

???? This dissolved gas causes pressure to build  

up resulting in a volcanic eruption

▪ Low viscosity (more mafic in nature) the dissolves  

gasses are allowed to escape through the volcanic  We also discuss several other topics like What makes notes troublesome at times when it comes to mortgage loans?
We also discuss several other topics like What makes bill clinton an effective president?

vent therefore pressure does not build up

???? No pressure means no explosion

Terms to know for location of molten lava

• Lava: molten rock erupted onto the Earth’s surface • Magma: molten material still within the Earth’s Surface • Both lava and magma are present in the plumbing of all  volcanic systems

What is the largest type of volcano?

o Magma becomes lava

o If lava flows back underground then it can become  magma again

Lava types (both between 1000-1200 degrees and move at variable  rates-fats or slow)

• Aa

o If you were to walk over this you’d probably say  


o Variety of solidified lava is generally crumbly with sharp  jagged edges

o Angular and jagged

▪ Blocky when rolling down hill

o Will be crumbly on the top and bottom with molten  material in the center We also discuss several other topics like What is the most common type of extracurricular activity?

o Rate or movement it flows depends on the slope  

gradient and pressure following the flow

▪ Most common flow speed is rapid but can varey

• Pahoehoe

o Will stand in stark

o Very smooth and tends to fold like fine fabric

▪ Ropey texture, flow slow and smooth

o Most common flow speed is slow and silky

The three categories for volcanoes If you want to learn more check out How do you get skeletal muscle to contract?

• Broad brushed concepts

• No volcano is typical and its behavior can deviate from  “typical characteristics” at any given moment

• Three types

o Shield  

▪ Largest type of volcano

???? Largest mountains in the world

• From ocean floor to the top of volcano

▪ Very shallow slopes (2˚ at base, 10˚ at top)

▪ Basaltic lavas- dark, black

???? Primary mafic

???? Low viscosity

▪ Almost exclusively lava

???? Feed by magma that is rising deep from the  We also discuss several other topics like What are the 5 stages in the cell cycle?


???? Material ejected from the central cone is  

primary flowing lava of both aa and  


???? Can stretch for miles

▪ Once the magma center has moved from the hot  

spot, the volcano will no longer be supplied with  

eruptible material

▪ Example: Hawaii

???? Mauna Kea and Mauna Lou

o Composite If you want to learn more check out How did the meccans receive mohammad's message?

▪ Large volcano (typically 8,000 feet high)

???? Height begins at Earth’s surface and not sea  


▪ Classic volcano shape, concave upward slopes  

(15˚ at base, 30˚ at top)

???? Steep sides

▪ Mostly intermediate compositions

???? But do to the ash it is also mafic

▪ Lave flows mixed with pyroclastic eruptions

???? Lave flow and pyroclastic

???? Lava flow: hard, resistant pyroclastic  

???? Material: soft, easily erode

▪ Consists of layers

???? Lava, ash, lava, ash, etc.

▪ Added silica make them explosive

???? When the dissolved gasses increase in  

concentration, it will result in a build up of  


???? When pressure is released, large quantities  

of hot ash and volatile will be expelled as a  

fiery could

• These clouds are known as

o Nuees ardentes  

o Pyroclastic flow

• These clouds destroy anything in its  


▪ Example: Mount St. Helen

???? Civilians knew for about a week and a half

???? 57 deaths

o Cinder Cone

▪ Smallest type of volcano

▪ Very steep slopes (30˚-40˚)

▪ Exclusively pyroclastic material

???? Volcanic bombs as well

???? The cone is primarily pyroclastic material or  

bombs that have been ejected from the  


▪ Generally subsidiary structures on the flanks of  

larger volcanoes

???? Similar to pimples on the side of bigger  


▪ Not long lasting

???? Small amounts of lava

• Mostly lava erupts from the base  

rather than the vent

▪ Mostly found in Colorado and Arizona

Pyroclastic flow cloud

• Destroy anything it comes across

• Consist of temperatures of 800˚

• Can glow red in the dark

• It can create its own lightning

• Moves at around 100 mph

• Can create volcanic bombs, or drop stone

o Ejected material that are typically large

• Killed Maurice and Katia Kraft

Volcanic inheritance

• It is likely that a new volcano will grow close to or in the  same location as the that just exploded

• A volcano can blow its self out of existence and due to  volcanic inheritance, we can have another volcano in the  same spot

Fissure eruptions

• Hydrothermal vents or geysers

o Occur sure to the ground water coming into contact  with rocks that have been heated due to magma in the  substance

o The ground water flows along until it comes into contact  with the hot material

o The water will become heated till it begins to boil, the  boiling action will force the liquid to the surface

o The resulting explosion fluid is called geyser

• Lava spews out from a fissure (fracture)

o No volcanic cone, therefore not a type of volcano

▪ Mostly cracks on Earth’s surface

o Very low-viscosity, basaltic lavas (water like), called  flood lavas

• Deccan traps

o Green house dinosaur extinction theory

▪ Assist extinction

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