Flashcards in Lecture #8 -Volcanoes Deck (46):
Where are most volcanoes occur?
Located near plate boundaries
What is Magma?
liquid rock found deep within the crust and upper mantle
What is Lava?
Liquid rock found drown for and erupting volcano (basically magma the reaches earths surface)
What are the most abundant elements in magma?
Silica and Oxygen
-together they form silica
What is the order of rocks from lowest to highest
What does a higher silica content produce?
a bigger explosion
What determines the shapes of volcanoes?
Chemistry and viscosity of magma
What are characteristics of magma with a high silica content?
What are characteristics of magma with a low silica content?
not as explosive
What are the 4 types of Volcanoes?
3. Volcanic Domes
Characteristics of Sheild Volcanoes
Form from lava(erupts, cools hardens)
Not really explosive
What is Tephra?
A general term for fragmented material ejected during an explosion
Characteristic of Shield Volcanoes?
Form from lava flow and pyroclastic deposits
Andesitic or Dacitic
Eruptions more explosive but less frequent
Characteristics of Volcanic Domes?
Highly viscous rhyolitic magma
Steep sided mounts that form around vents
Characteristics of Cinder Cone volcanoes
smaller volcanoes made from small pieces of tephra
Round--> oval Shape
Contain a crater at the top of the volcanoe
What is a Maars?
Circular volcanic craters produced by an explosive eruption and fill with water
What Causes Maars?
When groundwater comes into contact with magma which creates an explosion
What are Ice Volcanoes?
When volcanoes erupt beneath or against glaciers
What do Ice volcanoes produce?
-when magma melts large quantities of ice and produce floods
What is a crater?
Depression formed by the explosion or collapse of a volcano top.
-up to 2km in diamerter
What is a volcanic vent?
An opening on the surface through which lava and pyroclastic debris erupt.
Does lava always erupt out of the top?
No, can erupt from fissures in the side
what is a Caldera
Circular to oval depression formed during the collapse of a volcano.
-Up to 25km in diameter
How do calderas form?
The collapse of a magma chamber below a composite volcano during an explosive eruption. The chamber become empty and pressures decreases so it doesn't have the support and therefore collapses
What is a hot spring?
Heated groundwater that discharges at the surface
What is a geyser?
ground water that boils in an underground chamber and periodically produce a release of steam or water
When does Old faithful erupt?
Found in Yellowstone National Park
Erupts for 2-3 mins
every 70 mins
what are Super eruptions
Are the products of super volcanoes and are hella rare
-occur when a high volume of magma rises and is unable to break though the crust until enough pressure builds up
Subduction Zone volcanoe characteristics
Composite volcanoes found here
Mid ocean ridge volcano characteristics
Characteristics of volcanoes at hot spots beneath the ocean
Chains of Shield Volcanoes
Characteristics of volcanoes at hotspots beneath continental crust
Commonly forms Claderas
Why arent death tolls higher for volcanoes?
They occur in high mountain ranges and not a lot of people live there
What are some primary effects of volcanoes
What are some secondary effects of volcanoes?
What is Pahoehoe lava?
When hardened has a smooth texture
What is AA lava?
When hardened has a blocky texture
What is a Pyroclastic Flow?
Avalanches of ash, gas and rock fragments that travel down the slope of a volcano during an explosive eruption
- more people have actually died form these than an actual explosion
What is an Ash fall?
particles of ash can be carried downwind hindered of km form the eruption site
What is a Sector Collapse?
Flank of volcanoes can collapse at any time
-as magma travels up the channel, it can inflate and its slopes can be oversteepened
What is a Lahar?
Large amount of material that become saturated with water and moves downslope
Characteristics of Mt St Helen?
-small explosions were evident due to ground water contacting magma
-Bulge began to grown on the flank of the mountain
-M 5.1 quake caused the bulge to break off
-Lateral blast occurred
-57 people died mainly because of pyroclastic flows
-left behind a barren landscape
What other hazards can volcanoes cause?
-Lava can catch things on fire
What are natural service functions of volcanoes?
Provided gases that sustain the atmosphere
Geothermal energy and heat
Attract tourism and recreation
Creates new land
How do we minimize Volcanic hazards?
1. Monitoring seismic activity
2. Thermal and hydraulic monitoring
3. Land Surface monitoring
4. Monitoring volcanic gas emissions
5. understanding local and geologic history