Lecture #8 -Volcanoes

Question 1

Where are most volcanoes occur?

Answer 1

Located near plate boundaries

Question 2

What is Magma?

Answer 2

liquid rock found deep within the crust and upper mantle

Question 3

What is Lava?

Answer 3

Liquid rock found drown for and erupting volcano (basically magma the reaches earths surface)

Question 4

What are the most abundant elements in magma?

Answer 4

Silica and Oxygen

-together they form silica

Question 5

What is the order of rocks from lowest to highest

Answer 5

Basalt
Andesite
Dacite
Rhyolite

Question 6

What does a higher silica content produce?

Answer 6

a bigger explosion

Question 7

What determines the shapes of volcanoes?

Answer 7

Chemistry and viscosity of magma

Question 8

What are characteristics of magma with a high silica content?

Answer 8

Cooler
More viscous
More gases
explosive eruption

Question 9

What are characteristics of magma with a low silica content?

Answer 9

Hotter
less viscous
Fewer gases
not as explosive

Question 10

What are the 4 types of Volcanoes?

Answer 10

1. Shield
2. Composite
3. Volcanic Domes
4. Cinder Cones

Question 11

Characteristics of Sheild Volcanoes

Answer 11

Form from lava(erupts, cools hardens)
basaltic magma
Not really explosive

Question 12

What is Tephra?

Answer 12

A general term for fragmented material ejected during an explosion

Question 13

Characteristic of Shield Volcanoes?

Answer 13

Form from lava flow and pyroclastic deposits
Andesitic or Dacitic
Eruptions more explosive but less frequent

Question 14

Characteristics of Volcanic Domes?

Answer 14

Highly viscous rhyolitic magma

Steep sided mounts that form around vents

Question 15

Characteristics of Cinder Cone volcanoes

Answer 15

smaller volcanoes made from small pieces of tephra
Round–> oval Shape
Contain a crater at the top of the volcanoe

Question 16

What is a Maars?

Answer 16

Circular volcanic craters produced by an explosive eruption and fill with water

Question 17

What Causes Maars?

Answer 17

When groundwater comes into contact with magma which creates an explosion

Question 18

What are Ice Volcanoes?

Answer 18

When volcanoes erupt beneath or against glaciers

Question 19

What do Ice volcanoes produce?

Answer 19

jökuhloups

-when magma melts large quantities of ice and produce floods

Question 20

What is a crater?

Answer 20

Depression formed by the explosion or collapse of a volcano top.
-up to 2km in diamerter

Question 21

What is a volcanic vent?

Answer 21

An opening on the surface through which lava and pyroclastic debris erupt.

Question 22

Does lava always erupt out of the top?

Answer 22

No, can erupt from fissures in the side

Question 23

what is a Caldera

Answer 23

Circular to oval depression formed during the collapse of a volcano.
-Up to 25km in diameter

Question 24

How do calderas form?

Answer 24

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

Question 25

What is a hot spring?

Answer 25

Heated groundwater that discharges at the surface

Question 26

What is a geyser?

Answer 26

ground water that boils in an underground chamber and periodically produce a release of steam or water

Question 27

When does Old faithful erupt?

Answer 27

Found in Yellowstone National Park Erupts for 2-3 mins every 70 mins 50m high

Question 28

what are Super eruptions

Answer 28

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

Question 29

Subduction Zone volcanoe characteristics

Answer 29

Andesite | Composite volcanoes found here

Question 30

Mid ocean ridge volcano characteristics

Answer 30

Basaltic | Shield volcanoes

Question 31

Characteristics of volcanoes at hot spots beneath the ocean

Answer 31

Basaltic Chains of Shield Volcanoes -Islands

Question 32

Characteristics of volcanoes at hotspots beneath continental crust

Answer 32

Rhyolitic Explosive eruptions Commonly forms Claderas Ex: Yellowstone

Question 33

Why arent death tolls higher for volcanoes?

Answer 33

They occur in high mountain ranges and not a lot of people live there

Question 34

What are some primary effects of volcanoes

Answer 34

Lava flows pyroclastic flow Ash falls lateral blasts

Question 35

What are some secondary effects of volcanoes?

Answer 35

``` Landslides Floods Fires Tsunamis Lahars ```

Question 36

What is Pahoehoe lava?

Answer 36

low viscosity Really hot When hardened has a smooth texture

Question 37

What is AA lava?

Answer 37

High viscosity lower temperatures When hardened has a blocky texture

Question 38

What is a Pyroclastic Flow?

Answer 38

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

Question 39

What is an Ash fall?

Answer 39

particles of ash can be carried downwind hindered of km form the eruption site

Question 40

What is a Sector Collapse?

Answer 40

Flank of volcanoes can collapse at any time | -as magma travels up the channel, it can inflate and its slopes can be oversteepened

Question 41

What is a Lahar?

Answer 41

Large amount of material that become saturated with water and moves downslope

Question 42

Characteristics of Mt St Helen?

Answer 42

March 1980 - 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

Question 43

What other hazards can volcanoes cause?

Answer 43

- Lava can catch things on fire - Earthquakes - Landslide - Jökulhaups

Question 44

What are natural service functions of volcanoes?

Answer 44

Provided gases that sustain the atmosphere Geothermal energy and heat Attract tourism and recreation Creates new land

Question 45

How do we minimize Volcanic hazards?

Answer 45

1. Monitoring seismic activity 2. Thermal and hydraulic monitoring 3. Land Surface monitoring 4. Monitoring volcanic gas emissions 5. understanding local and geologic history

Question 46

What are the 3 methods in attempting to divert lava flows?

Answer 46

1. Bombing- forcing channel to an alternate rout 2. Hydraulic Chilling- water used to chill and cool lava 3. wall Construction- Wall redirecting