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Transcript of Volcanoes
Intro to Volcanoes
What they are in a nutshell
Geographic Regions at Risk for Volcanoes
Volcanoes mostly occur along the "Ring of fire" which is the Pacific ocean basin. However places outside this area can experience volcanoes they are located on portions of the mid-ocean ridge. [ Hawai'i, Iceland]
Effects of Volcanoes
Linkages between Volcanoes and Other Natural Hazards
Volcanoes are directly linked to fires, earthquakes, landslides, and climate change
1.) Molten rock that is produced through the interaction of lithospheric plates with other earth material.
What magma is considered when it erupts onto the earth's surface
1. Shield Volcanoes
Craters: Depressions that are found at the top of volcanoes.
Mid - ocean ridges: produces basaltic magma coming directly from the asthenosphere.
The result of magma reaching the surface and overflowing the central crater.
refers to the explosive volcanism in which tephra is physically blown from a volcanic vent into the atmosphere.
There are many kinds of gases emitted during volcanic activity.
Debris Flows, Mudflows, and Other Mass Movements
These are all secondary effects of volcanic activity.
Mount St. Helens
In 1980, the cascade volcano awoke from dormancy due to small explosions caused by the boiling of the ground water.
By May, there was a prominent bulge on the northern flank of the mountain.
Weeks later an earthquake below the volcano triggered a landslide/debris avalanche.
Then The Mount erupted with a lateral blast which led to the large vertical cloud and pyroclastic flow. There was also much more devastation.
Minimizing the Volcanic Hazard
2.) composed of silicate minerals and dissolved gases. (SiO2)
3.) 3 major types of magma: basaltic, andesitic, rhyoltic
4.) they differ by the silica content in each rock. (basaltic having the lowest of the three)
5.) viscosity and gas content:
- the greater the silica, the more difficult magma flows
- the higher the gas content, the more likely for an explosive eruption.
the largest volcanoes in the world
2. Composite Volcanoes
are more viscous than shield volcanoes and are also known as stratovolcanoes.
3. Volcanic Domes
characterized by highly viscous magma
4. Cinder cones
relatively small volcanoes composed of nut to fist sized pieces of red or black lava.
Subduction zones: composite volcanoes are associated with this zone, so it is commonly found around the pacific rim.
Hot spots beneath the oceans: Shield volcanoes are formed above hot spots in the oceanic lithosphere.
Hot spots beneath continents: Caldera- forming eruptions occur here. Meaning they can be extremely violent and explosive, generally associated with rhyolitic magma.
Calderas: They are depressions formed during explosive ejection of magma and relating collapse of the upper cone.
Vents: Any opening that can allow lava and pyroclastic debris to go through during eruption.
Hot spring: Also known as a thermal spring is the contact of groundwater with hot rock.
Geyser: Less common and it is the release of steam and hot water at the surface.
Caldera Eruptions: They are the type of eruptions that produce calderas.
Earthquakes: commonly accompany or precede volcanic eruptions as magma rises through Earth's crust
Fires: lava pours down the sides of a volcano and plants of human-built structures catch fire
Landslides: most common side effect
Climate Change: eruption can create global clouds of sulfuric acid droplets; the cloud can then cause regional cooling
Natural Service Functions of Volcanoes
It is believed that billions of yrs ago gases and water vapor that were released from volcanoes began to form our atmosphere & hydrologic systems allowing life to evolve
Lava flow can be quite fluid or move slowly depends on the type of lava.
source of power
Nutrients are produced by weathering of volcanic rocks which allows crops to thrive in volcanic soils
-coffee, sugar cane, and grapes as well as many more
However, these rich soils encourage people to live nearby volcanic activity which makes it difficult to safely use the resource.
Internal heat may be used to create power for nearby urban areas
Ex: This is done in parts of Hawaii and California
This geothermal power is a renewable resource. It can be used at a rate that it does not outpace replenishment
types of activity:
- Ash fall
- lateral blasts
- pyroclastic flows
Volcanic rocks are the host for many mineral resources
-metals: gold, silver, platinum, copper, nickel, lead, and zinc
-nonmetallic: pumice, tuff, perlite, scoria, baslat, and volcanic clays
*Most of these metallic mineral resources are found in much older Precambrian rocks
Many health spas and hot springs are developed in volcanic areas.
They also provide opportunities for hiking, snow sports, and education.
Creation of New Land
Volcanoes are responsible for creating much of the land we inhabit.
Volcanic processes are the major force that builds continents as well as oceanic islands such as Hawaii and Iceland.
gases like water vapor
Hydrogen Sulfide (H2s)
Debris flows: are the flood meltwater that erodes the slope of the volcano and creates the debris flow.
Human Interaction with Volcanoes
There does not appear to be any human activity that affects volcanoes.
There is little we can do to affect timing and severity of their eruptions.
Mudflows: large amounts of loose volcanic ash that is saturated with water becomes unstable and moves downslope.
Landslides: maybe triggered by events other than eruption
1. What is the difference between magma and lava?
2.What other natural hazards are linked to volcanoes?
3. What are two benefits of volcanoes?
4. What are two ways to control lava flow?
5. What are the major gases emitted in a volcanic eruption?
6. What are the primary effects of volcanoes?
7. What are the secondary effects of volcanoes?
8. What are the major types of volcanoes and their eruption styles?
9. What is viscosity and what determines it?
10. Explain the relationship between plate tectonics and volcanoes.
monitoring seismic activity
monitoring thermal, magnetic, and hydrological conditions
monitoring the land surface to detect tilting or swelling of the volcano
monitoring volcanic gas emissions
studying the geological history of a particular volcano or volcanic center
Volcanic Alert or Warning
normal - typical background, non-eruptive state
advisory - elevated unrest above known background level
watch - eruption underway with limited hazards; for aviation-no or minor volcanic ash emissions
warning - hazardous eruption imminent, underway, or suspected,; for aviation-significant emission of volcanic ash into atmosphere
Perception of and Adjustment to the Volcanic Hazard
Adjustments to Volcanic Hazards
the best way to avoid a volcanic hazard is to evacuate the area and follow directions from officials
Attempts to Control Lava Flows
hydraulic chilling and wall construction help to keep lava flows away from populated areas
Amanda,Morgan and Michelle