Parts of a Volcano 1. Gas emission: various gases such as CO2,

H2O, nitrogen, and lesser gases such as chlorine, hydrogen, and argon.

2. Crater: depression connected to magma chamber via a pipe aka caldera

3. Lava: magma that has reached the surface 4. Rock 5. Vent or pipe: conduit that connects magma

chamber to the crater 6. Magma chamber: area where magma accumulates within the

volcano 7. Fumorale: vent that emits only gases

Anatomy Of A Volcanic Eruption!1. Intense heat from magma cracks the rocks near the

surface. The cracking rock produces an earthquake!!2. Hot blasts of high pressure gases expand the cracks and

develop a passage to the surface. 3. Hot gases with rock fragments create a larger conduit or

pipe. Volcanic pipes are created due to increase in pressure. A bulge is created due to gas build up.

4. Pipes enlarge, magma moves upward to produce an eruption.

5. Pipes can become clogged with cooled magma and debris. Gas pressure can build up an cause another eruption.

What determines how violent an eruption will be? The viscosity of the magma determines

how violent an eruption will be.

What is viscosity? The resistance of material to flow. A very viscous material is very thick and

flows slowly. When thinking of a volcano…the more

viscous the magma is, the more explosive the eruption will be!

What influences the viscosity of magma? Temperature Chemical composition of the magma Amount of dissolved gases (H2O and

CO2)

Temperature Fluidity (flow) and mobility (movement) is

strongly influenced by temperature. Cool lava congeals (becomes solid) just

like making jello. The mobility and flow stops.

Magma Chemical Composition Viscosity is directly related to silica content. The more silica the greater the viscosity. Flow is slowed due to the long chains of silica

molecules Felsic(high in silica) very viscous, short, thick flows. Mafic (low in silica) quite fluid, travels long

distances

Dissolved Gases Dissolved gases increase the fluidity of

magma. Escaping gases expand as pressure

decreases. This provides the force to propel molten

rock.

Non-explosive Eruptions Fluid lava (basalt) magma allows for

expanding gases to be released with ease. Release huge amount of lava Most common type of volcanic eruption The northwest U.S. region, the Hawaiian

Islands and the mid-ocean-ridge are all examples of non-explosive eruptions.

Explosive Eruptions Highly viscous magmas explosively expel

jets of hot ash, gases, and other debris. Instead of producing lava flows, explosive

eruptions cause molten rock to be blown into tiny particles (thousands of fragments of glass)

Examples of explosive eruptions: Mt. St. Helen’s, Mt Pinatubo in the Philippines

Effects of Volcanic Eruptions Volcanic ash and gases spread throughout

the atmosphere. They can block out enough sunlight to

cause global temperatures to drop.

Effects of the Mount Tambora eruption (1815) on humanity: Ash blanketed the skies of Indonesia and caused 3 days of

total darkness. Estimated that 12,000 people died directly from the blast. 80,000 people died from the resulting hunger and disease. caused global temperature to drop affected the global climate a year later affected temperatures enough to cause food shortages in

N.America and Europe The summer was called the Summer of Starvation.

Volcano Types Plumes Shield Cinder cone Composite or Stratovolcano

Plumes stationary hot spots erupt as volcanoes Magma comes from deep within the mantle. As crust moves, the volcano will move off hot

spot and become extinct. A new volcano will form. example: Hawaiian Island Chain

Hot Spots Volcanically active places on Earth’s surface that

are far from plate boundaries OR Another theory is that hot spots are magma

plumes along cracks in the plates. Hot spots always form long chains of islands. What theory is true??? Yellowstone is a hot spot. It is unusual to have a

hot spot under a continent.

Shield Volcano Built of layers of lava released from

repeated non-explosive eruptions Lava is runny and spreads out over a wide

area. Layers of lava create a volcano with gently

sloping sides Although they are not steep, they are

enormous in size.

Shield Volcano

Cinder Cone Volcano Made of pyroclastic material usually produced

from moderately explosive eruptions Usually small and erupt for only a short period of

time. Forms steep slopes. Usually occurs in clusters, commonly on the sides

of other volcanoes Erode quickly due to loose pyroclastic material

Cinder Cones

Composite Volcano aka Stratovolcano Most common, nearly symmetrical structure Composed of alternating lava follows ad

pyroclastic material Produced from relatively viscous lavas, may

extrude lava for a long period, or suddenly erupt violently.

Broad bases and steep sides Examples: Western region of the U.S. includes

Mt. Hood, Mt. Rainier, Mt Shasta, and Mt St. Helen.

Composite Volcano

Sea Vents

A sea vent is a fracture or crack in the ocean floor where pressure is constantly being released.Interesting life forms live there.No sunlight, only chemicals to survive onThis is the only place on Earth where organisms don’t rely on the sun.

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