Ch. 13 - Tectonics, Earthquakes, Volcanism Flashcards
What kind of faults happen as a result of Tension deformation of crust?
Normal Faults (One side drops in respect to the other)
What kind of faults/formations can happen from Compression?
Reverse Faults, Folding
What kind of faults/formations occur as a result of Shear force (sliding past one another)?
Horizontal Bending, Strike-Slip Faults
What is an Anticline?
Upfolded rock strata in which layers slope downward from the axis of the fold, or central ridge
What is a Syncline?
A trough in folded strata, with beds that slope toward the axis of the downfold
What are the four ways that Crustal Formation can happen?
- Divergent – Oceanic/Oceanic, Continental/Continental
- Hot Spots
- Convergent – Oceanic/Oceanic, Oceanic/Continental
- Cratons + Terrane
What are the two causes of Earthquakes? How do they happen?
Elastic Rebound + Asperities (The small areas that are sticking points along a fault are points of high strain. When these sticking points break, they release the sides of the fault)
Foreshocks (A quake that precedes the main shock)
What is a Terrane?
A migrating piece of Earth’s crust, dragged about by processes of mantle convection and plate tectonics. Displaced terranes are distinct in their history, composition, and structure from the continents that accept them
What is a Craton?
A large stable block of the earth’s crust forming the nucleus of a continent.
What is the instrument used to measure earthquakes?
Seismometer
What kind of waves are created from Earthquakes releasing energy?
Seismic Waves
What are the two types of Seismic Waves?
Body Wave
Surface Waves
What are the characteristics of Body Waves?
Radiate out at the same time
- P wave (Primary) This wave will be recorded first/travels faster/ more direct
- S wave (Secondary) Same origin, but not as direct due to up and down motion
What are the characteristics of Surface Waves?
They travel along the earth’s surface, but have the same origin. They move slower than Body Waves
What is the “Focus” of an earthquake?
The focus is the point within the earth where seismic waves originate; it is centered on the part of the fault that has the greatest movement
What is the “Epicenter” of an earthquake?
Is the point on the earth’s surface directly above the Focus of the earthquake
What are the three methods of measuring earthquakes?
Richter Scale
Modified Mercalli Scale
Moment Magnitude Scale
How does a Richter Scale work?
Oldest method; done by looking at amplitude on a seismometer.
Each number increase is a tenfold increase in wave amplitude
How does a Moment Magnitude Scale work?
Involves Rock Rigidity + Fault Area + Slip Distance
How does a Modified Mercalli Scale work?
Measures the intensity of an earthquake.
Measured by the damage of infrastructure, and effect on human beings
Usually on a scale of 1 to 12
What are the main effects of earthquakes?
- Ground motion (doesn’t necessarily harm people)
- Falling objects/debris (this is the aspect that actually harms people)
- Fire/Gas leaks
- Landslides
- Liquefaction
- Tsunamis
What is a Megathrust Earthquake?
An earthquake with a magnitude above 9.0. These are said to happen roughly once every 500 years in the PNW region of North America.
The last Megathrust happened January 26th 1700
What are the three types of magma?
Rhyolitic (Highest silica content, has high viscosity)
Andesitic (hardens quickly when it reaches the surface)
Basaltic (least amount of Silica; magma is very liquidy and flowy)
What are the two main types of Lava?
Pahoehoe
Aa
