Volcanoes and Earthquakes Flashcards
(31 cards)
How often do earthquakes and volcanoes occur at plate boundaries?
Most earthquakes/volcanoes occur along plate boundaries
90% major earthquakes
94% active volcanoes
Define Earthquake
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
Define Epicenter
The area at the surface directly above the focus of the earthquake
What is the likelihood of an earthquake at different boundaries?
Convergent: highest likelihood of severe earthquake
Transform (Strike-Slip): lower likelihood of severe earthquake
Normal: lowest likelihood of severe earthquake
What is the name for molten material at the earth’s surface?
Lava
Define Volcano
Vent in the earth’s surface where molten material and gasses are released with a cone formed around the vent
What kinds of faulting can result in an earthquake?
Any faulting can result in an earthquake
What is a fault scarp and where is it found?
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
What is a Reverse Fault?
Compressional forces pushing one piece over the other piece
The San Andreas Fault is an example of what kind of fault?
Strike/Slip Fault (Orogeny at Convergent)
-folding, deformation along fault due to catching as pieces slide against one another
What is an Oblique-Slip Fault?
A fault with both horizontal and vertical offset (picture of scene where fence line used to be straight)
How does amount of energy effect an earthquake?
The amount of energy is directly related to the intensity of the outcome
What effect of an earthquake generally don’t kill you?
- Ground surface rupture
- Fissures and cracks
- Ground displacement (subsidence, uplift)
- Landslide
- Liquefaction
- Tsunami
- Flood
What secondary effect from an earthquake are more likely to kill you?
-Building/infrastructure collapse
-Utility failure
-Fire
-Dam failure
-Hazardous material spills
(ie- manmade stuff)
What influences the type of volcano seen?
Viscosity of the material (temperature and type- felsic or mafic)
What are the 2 eruption types?
Explosive and Effusive
Define an Explosive volcano
Volcanic activity along subduction zones = Composite (most dangerous kind)
Describe Effusive Eruptions
- 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
Describe a Shield Volcano
- 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
Describe a Plateau (Flood) Basalt
- 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
Describe Explosive Eruptions
- 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
Give details about the 1815 Tambura Eruption
- 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
What are Cinder Cones?
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
What is a Composite Volcano?
Classic cone-shaped volcano
- Explosive
- Repeated eruptions over time
- Layers of solidified tephra and lava flow
- ie “Strata Volcanoes”
