Welcome geology 111 volcanoes
Download
1 / 36

Welcome ! Geology 111 Volcanoes - PowerPoint PPT Presentation


Welcome ! Geology 111 Volcanoes. Dr Ken Sprenke www.mines.uidaho.edu/~sprenke. Explosive eruptions are favored by high gas content and high viscosity (andesitic to rhyolitic magmas). Expansion of gas bubbles is resisted by high viscosity of magma - results in building of pressure

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha

Download Presentation

Welcome ! Geology 111 Volcanoes

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Welcome geology 111 volcanoes l.jpg

Welcome !Geology 111Volcanoes

Dr Ken Sprenke

www.mines.uidaho.edu/~sprenke


Slide4 l.jpg

Explosive eruptions are favored by high gas content and high viscosity (andesitic to rhyolitic magmas).

  • Expansion of gas bubbles is resisted by high viscosity of magma - results in building of pressure

  • High pressure in gas bubbles causes the bubbles to burst when reaching the low pressure at the Earth's surface.


Slide5 l.jpg

Bursting of bubbles fragments the magma into pyroclastsandtephra (ash).


Slide6 l.jpg

Cloud of gas and tephra rises above volcano to produce an eruption column that can rise up to 45 km into the atmosphere.


Slide7 l.jpg

Tephra that falls from the eruption column produces a tephra fall deposit.


Slide8 l.jpg

If eruption column collapses a pyroclastic flow  may occur, wherein gas and tephra rush down the flanks of the volcano at high speed.  This is the most dangerous type of volcanic eruption. 


Slide9 l.jpg

After the lateral blast on Mt St.Helens, pyroclastic flows of hot gas and ash raced down the mountain.


Slide10 l.jpg

Pyroclastic flows from Mt Vesuvius instantly killed and entombed the citizens of Pompei and Herculaneum in 79 AD.


Slide11 l.jpg

Lateral blasts and debris avalanches occur when gas is released suddenly by a large landslide taking out part of the volcano.


Slide13 l.jpg

Shield volcano.


Slide14 l.jpg

Mauna Loa: A shield volcano.


Slide15 l.jpg

An extinct shield volcano


Slide16 l.jpg

Fissure Eruptions - An eruption that occurs along a narrow crack or fissure in the Earth's surface.


Slide17 l.jpg

Most flows in the Columbia Plateau erupted from fissures.


Slide18 l.jpg

Flow surfaces:

aa ---- rough

pahoehoe --smooth ropy texture


Slide19 l.jpg

Hexagonal columns form as lava shrinks. The columns grow perpendicular to the cooling surface.


Slide20 l.jpg

Pressure ridges: buckling of the lava surface due to stress

while the lava is cooling.


Slide21 l.jpg

Lava tube: A tunnel below the solid surface of a flow where lava continued to flow.


Slide22 l.jpg

Spatter cone: small steep-sided cone formed from molten material thrown into air that falls back to surface and adheres together.


Slide23 l.jpg

200 m high cinder cone in California.


Slide24 l.jpg

Eldfell: a 300 ft high cinder cone that appeared suddenly in 1973.


Slide25 l.jpg

Stratovolcano (composite volcano) - a volcano built of interbedded lava flows and pyroclastic material.


Slide26 l.jpg

Composite (strato-) volcano


Slide27 l.jpg

Composite volcano in the Phillipines.


Slide28 l.jpg

St.Helens before it blew up: a stratovolcano..


Slide29 l.jpg

Crater - a depression caused by explosive ejection of magma or gas

A typical summit crater on a cinder cone.


Slide30 l.jpg

Caldera - a depression caused by collapse of a volcano into the cavity once occupied by magma


Slide31 l.jpg

Formation of Crater Lake.

Is Crater Lake a crater?

No! Crater Lake occupies a caldera.


Slide32 l.jpg

Mt Lassen--world’s largest lava dome.


Slide33 l.jpg

Some Volcanic Hazards

Nuee ardente--dense cloud of hot pyroclastic materials and gases.

Lahar: Mudflow composed

of volcanic materials

Volcanic gas emissions.


Slide34 l.jpg

Most volcanoes occur at convergent and divergent plate margins.


Slide35 l.jpg

Some volcanoes such as Yellowstone and Hawaii are caused

by mantle hot spots.


Slide36 l.jpg

Next Class: Case Study Pinatubo.


ad
  • Login