Tectonic Activities Flashcards
(27 cards)
What produces an earthquake?
The breaking of rock
What is the cause of earthquakes?
Plate movement
What is the Elastic Limit? How does it pertain to earthquakes?
The elastic limit is the point of no return. The elastic limit is exceeded when an earthquake is caused.
What is a fault?
A fracture in the Earth’s crust
What are the three main fault types?
Normal, reverse, and strike-slip
Where does each of the main fault types occur (boundary type)?
Normal:divergent
Reverse:convergent
Strike-slip:transform
What type of force is generated at each fault type?
Normal:tension
Reverse:compression
Strike-slip:shear
What is a seismic wave and how are they formed?
Seismic wave:energy waves
How:released when rock breaks
What is the focus and how does it differ from the epicenter?
Focus:point below ground where the rock is breaking
Epicenter is the ground directly above the focus
What are the three types of seismic waves?
P-wave, s-wave, surface wave
Where does each type of wave originate?
P-wave and S-wave:from the focus
Surface wave:from epicenter
How do the movements of seismic waves compare?
P-wave:particles move back and forth in the direction of the wave
S-wave:particles move at right angles to the direction of the wave
Surface:particles move in an elliptical pattern
How does the speed of seismic waves compare?
P-wave:fastest
S-wave:second fastest
Surface:slowest
Which seismic wave causes the most damage and why?
Surface wave, because it takes the most time to move and elliptical pattern is the most destructive and it’s above the ground.
How is distance determined to an epicenter?
Uses the difference in time of primary and secondary waves
Why is it necessary to have at least three stations for triangulation of an epicenter? Why won’t a single station work?
The earthquake could be anywhere on the radius of the circle, until you see three or more circles meet up in the same spot.
How have seismic waves been used to map the Earth’s interior?
Waves speed up and slow down in different parts of the interior, generally move faster through materials that are more dense and slower in materials that are less dense.
What is the Shadow Zone?
An area on the opposite side of the Earth from the earthquake focus
S-waves disappear from 105-180 degrees because they can’t pass through liquid
P-waves disappear from 105-142 degrees because they are deflected when they pass through liquid outer core
What are the two factors that determine the type of eruption?
- Amount of water vapor and other gases that are trapped in the magma
- Type of magma-basaltic or granitic
What are the main trapped gases?
Water vapor and carbon dioxide
Why are gases trapped in magma?
Because of surrounding pressure and the type of magma
Why is there so much water vapor associated with subduction zones?
Because an ocean plate goes under another which causes water vapor, because of the heat
What are the two types of magma?
Basaltic and granitic
How do the magma characteristics vary and how does this affect the type of eruption?
Basaltic:contains less silica and causes non-violent eruptions
Granitic:contains high amounts of silica, very thick, causes violent eruptions
