Lecture 03-06-2017

Question 1

Where are the majority of volcanoes found?

Answer 1

Overtop of intercontinental plate boundaries.

Question 2

Lava vs. magma

Answer 2

1. Lava is extrusive

2. Magma is intrusive

Question 3

Describe the process of magma to igneous rock.

Answer 3

Magma rises to earth’s surface, it intrudes into shallower rocks, minerals of different chemical compositions crystallize and solidify producing different igneous rocks.

Question 4

Plutonic intrusion vs. Hypabyssal intrusion

Answer 4

1. Plutonic intrusion are deep lying igneous rocks w/ big crystals
2. Hypabyssal intrusion are shallower than plutonic igneous rocks w/ small crystals.

Question 5

What are the 3 types of lavas?

Answer 5

1. Aa (pronounced “ah-ah”) OR Blocky Lava - reduced gas content, lava breaks up into a series of blocks at the surface
2. Pahoehoe (pronounced ‘paw-hoey-hoey”) OR Ropy Lava - retains gas, remains mobile for a long time, flows great distances, Ridges parallel to the flow direction
3. Pillow Lava - as a flow of lava advances downslope in a submarine location, the sea water chills the outer edge of the flow and creates a thin skin that under pressure from the molten lava beneath cracks that create pillows.

Question 6

1. Aa (pronounced “ah-ah”) OR Blocky Lava.

Answer 6

1. Reduced gas content

2. lava breaks up into a series of blocks at the surface

Question 7

2. Pahoehoe (pronounced ‘paw-hoey-hoey”) OR Ropy Lava

Answer 7

1. Retains gas
2. Flows great distances
3. Ridges parallel to the flow direction

Question 8

3. Pillow Lava

Answer 8

As a flow of lava advances downslope in a submarine location, the sea water chills the outer edge of the flow and creates a thin skin that under pressure from the molten lava beneath cracks that create pillows.

Question 9

Why can volcanic ash be blown and deposited so far away from the source of a volcanic eruption?

Answer 9

1. Ash is composed of very fine silt which is easily blown

2. It’s projected with tremendous force

Question 10

T or F: Bombing has been used as a method of redirecting lava flows to divert them away from from towns and cities.

Answer 10

True; Etna, Italy, 1992 (http://bigthink.com/eruptions/why-would-you-ever-bomb-a-volcano)

Question 11

What’s the goal of draining volcanic crater lakes?

Answer 11

To avert a violent eruption.

Question 12

What are some of the positive outcomes associated with Volcanic Eruptions?

Answer 12

1. Renewed mineral content in local soils
2. New real estate can be created (e.g., waterfront property)
3. Building aggregates (e.g., Scotland, volcanic basalt used as a local building material)
4. Industrial chemical applications (e.g., Borax cleaner comes from volcanic products).

Question 13

What is a Tiltmeter and what does it do?

Answer 13

A measuring device which uses the tilt of volcanic slopes to calculate the probability of eruption.

Question 14

How are geophysical measures used to calculate the probability of a volcanic eruption?

Answer 14

Heat; changes used to predict likelihood of eruption.

Question 15

T or F: The noise from volcanos can be used to help determine the probability that an eruption will occur.

Answer 15

T; Hawaii

Question 16

Where is the closest area with a heightened frequency of earthquakes?

Answer 16

St. Lawrence River Valley fault line - the vault trace IS the valley.

Question 17

1. Why are higher frequencies of earthquakes present in and around salt deposits?
2. Where does this occur in Canada?

Answer 17

1. Ground water intrudes and dissolves salt creating areas of instability
2. Faults going northeast and northwest in Alberta and Sask. are situated around margins where salt occurs.