Volcanoes and Earthquakes

Question 1

How often do earthquakes and volcanoes occur at plate boundaries?

Answer 1

Most earthquakes/volcanoes occur along plate boundaries
90% major earthquakes
94% active volcanoes

Question 2

Define Earthquake

Answer 2

A sudden slipping or movement of a portion of the earth’s crust resulting from release of accumulated stress, accompanied by a series of vibrations

Question 3

Define Epicenter

Answer 3

The area at the surface directly above the focus of the earthquake

Question 4

What is the likelihood of an earthquake at different boundaries?

Answer 4

Convergent: highest likelihood of severe earthquake
Transform (Strike-Slip): lower likelihood of severe earthquake
Normal: lowest likelihood of severe earthquake

Question 5

What is the name for molten material at the earth’s surface?

Answer 5

Lava

Question 6

Define Volcano

Answer 6

Vent in the earth’s surface where molten material and gasses are released with a cone formed around the vent

Question 7

What kinds of faulting can result in an earthquake?

Answer 7

Any faulting can result in an earthquake

Question 8

What is a fault scarp and where is it found?

Answer 8

A fault scarp is a verticle feature (can be about 20 feet difference in height from original altitude and can stretch on for miles)

• Substantial offset, as one piece drops down from the other piece
• Located at a Normal Fault

Question 9

What is a Reverse Fault?

Answer 9

Compressional forces pushing one piece over the other piece

Question 10

The San Andreas Fault is an example of what kind of fault?

Answer 10

Strike/Slip Fault (Orogeny at Convergent)

-folding, deformation along fault due to catching as pieces slide against one another

Question 11

What is an Oblique-Slip Fault?

Answer 11

A fault with both horizontal and vertical offset (picture of scene where fence line used to be straight)

Question 12

How does amount of energy effect an earthquake?

Answer 12

The amount of energy is directly related to the intensity of the outcome

Question 13

What effect of an earthquake generally don’t kill you?

Answer 13

• Ground surface rupture
• Fissures and cracks
• Ground displacement (subsidence, uplift)
• Landslide
• Liquefaction
• Tsunami
• Flood

Question 14

What secondary effect from an earthquake are more likely to kill you?

Answer 14

-Building/infrastructure collapse
-Utility failure
-Fire
-Dam failure
-Hazardous material spills
(ie- manmade stuff)

Question 15

What influences the type of volcano seen?

Answer 15

Viscosity of the material (temperature and type- felsic or mafic)

Question 16

What are the 2 eruption types?

Answer 16

Explosive and Effusive

Question 17

Define an Explosive volcano

Answer 17

Volcanic activity along subduction zones = Composite (most dangerous kind)

Question 18

Describe Effusive Eruptions

Answer 18

• Mafic material (lower viscosity, hotter, flows more easily, gasses in material are released easily)
• much gentler
• may flow out of central vent fissures
• Can occur at Hot Spot
• Divergent Plate Boundaries

Question 19

Describe a Shield Volcano

Answer 19

• Effusive
• Wider than it is tall
• Wide, thin layers of lava that slowly form the shield shape (built by multiple effusive eruptions)
• no steep sides
• Rainshadow possible

Question 20

Describe a Plateau (Flood) Basalt

Answer 20

• Effusive
• Mafic flow from elongated fissures
• “flood” of basalts
• “Devil’s Post Pile”
• cools through time, contracts and breaks into octagonal patterns that are naturally-occuring

Question 21

Describe Explosive Eruptions

Answer 21

• Felsic material
• more likely at Subduction Zones
• Viscous material, cooler, tends to plug up vents that cause a build up of pressure until sudden, violent release (explosion)
• Powerful, violent

Question 22

Give details about the 1815 Tambura Eruption

Answer 22

• Explosive
• Largest eruption in recorded history
• Radius of explosion 3.7 miles
• Ash reflected the sunlight causing insolation, “no summer” in 1816 caused famine in Europe and North America
• Estimated 92,000 deaths worldwide

Question 23

What are Cinder Cones?

Answer 23

Accumulation of tephra and scoria (cindery rock full of air bubbles) around and downward as molten material solidifies from vent

• cone formed around vent
• usually quickly warn away
• can occur at both types of volcanoes

Question 24

What is a Composite Volcano?

Answer 24

Classic cone-shaped volcano

• Explosive
• Repeated eruptions over time
• Layers of solidified tephra and lava flow
• ie “Strata Volcanoes”

Question 25

Describe a Crater

Answer 25

Bowl-shaped feature left by a volcanic explosion (old material tossed away by a volcano)

Question 26

Describe a Caldera

Answer 26

Basin-shaped depression left when a magma chamber collapses

-Collapsed feature with steep sided walls (may fill in later with water)

Question 27

How can a volcano kill you?

Answer 27

• Poisonous gasses (“quiet death”) like sudden CO2 release
• Ash and other ejecta (tephra)
• Pyroclastic flow
• Lava flow
• Lahars: glaciers melt on top of a volcano and slide down mixed with volcanic material
• Landslides

Question 28

What is found at Covergent boundaries?

Answer 28

Explosive Volcanoes

Reverse Faults

Question 29

What is found at Divergent boundaries?

Answer 29

Effusive Volcanoes

Normal Faults

Question 30

What is found at Transform boundaries?

Answer 30

Strike-Slip Faults

Question 31

What is found at Hot Spots?

Answer 31

Effusive Volcanoes