This site is 100% ad supported. Please add an exception to adblock for this site.

Geology- Lecture 2

Terms

undefined, object
copy deck
What happens when rocks fold closer to the surface? deeper in the earth?
surface: brittle (they fault) deeper: they're hotter so they fold
Define: Anticlines
a fold that looks like an A
Define: Syncline
a fold that looks like a U
Define: Symmetrical folds
the dips are the same
Define: Asymmetrical fold
dips are different
Define: overturned fold
the top of the layer is facing the bottom
Define: recumbent fold
extreme overturn, when the fold is on its side
Define: plunging anticlines and syncline
when they get tilted, the strike is pointing into the ground
What are two ways a rock can break?
Joints (fractures with no displacement) Faults (fractures with displacement)
Define: Joints
fractures with no displacement. Lots of pressure, then pressure is released. The rock fractures a simple crack in the rock
Define: Faults
fractures with displacement. rocks slip up and down
Define: dip-slip fault
the direction of movement is along the fault
What are some causes for rocks to respond to stress differently?
-type -magnitude of stress -pressure and temp -amount of fluid
Define: stress field
all the stress is placed on a rock
Define: Confining Pressure
a rock experiences pressure equally from all sides (normally at depths)
Define: Differential Stress
when one direction of stress is greater in one direction (additional stress comes from outside sources like tectonics)
Define: Fluid Pressure
reduces the outside pressure
How does Continental Crust act at: Shallow levels Increasing depth great depth
shallow: rocks fracture middle: rocks begin to deform deep: temp is more powerful than pressure so they begin to melt
What are the three types of stress?
Compressional (convergent forces) Tensional (divergent) Shear (transform)
Define: Compression
push together. shallow: fracture and slip deep: forms an anticline
Define: Tension
push away shallow: minerals get caught and make a vein deep: not as common, but still causes veins
Define: Shear
sidewise shallow: fault deep: creates a wavy looking rock
Define: Dip
if you pored water on the rock, where the water rolls off thats where the dip is
Define: Strike
if water floods the area, where the water line makes a horizontal line with the rock, the angle underneath is the strike
Define: Strike-Slip Fault
One rock moves left or right relative to the other rock
Define: Oblique Slip Fault
One rock moves left/right and up/down to the other rock
What are the three types of faults
Normal fault (hanging wall moves down) Reverse Fault (hanging wall moves up) Strike Slip Fault (rock moves side to side)
Define: Normal Fault
hanging wall moves down relative to footwall rocks are pulled apart and lengthened
Define: Reverse Fault
when the hanging wall moves up relative to the footwall rocks are compressed and shorten rock unit
Define: Thrust fault
a reverse fault that has a gentle dip
Define: Strike Slip Fault
when the rocks move side to side
Define: Monocline
nearly flat layers dip in one direction and then flatten
Define: hinge/fold axis
the most sharply curved part
Define: Plunge
the direction and amount that the fold points downward
Define: Axial Surface
an imaginary plane that cuts through the rock at the hinge. It can either be upright or at an incline
Define: Asymmetric fold
when the axial surface is at an incline
Define: Overturned
When the left/right limb has been rotated more than 90 degrees
What are the steps in an earthquake?
original position --> Deformation --> Rupture and release of energy --> Rocks rebound to original undeformed shape
Define: Elastic Rebound
earthquakes build up a lot of stress, then with an earthquake the stress is relieved
define: liquefaction
solid material behaves like an liquid (pouring sand)
Define: Hypocenter
the place where the earthquake is generated (usually at some depth within the earth)
Define: Epicenter
the point on earth's surface directly above where the earthquake occurs (can be the same place as the hypocenter)
What causes most earthquakes
plate boundaries
What are most of the major causes of earthquakes (5)
-plate boundaries -a volcanic eruption -land slide -nuclear bomb test -meteorite impact
Where do small earthquakes occur
at mid ocean rides they are shallow and relatively small
Where do large earthquakes occur?
along the entire contact between the subducting plate and the overriding plate
What kinds of seismic waves do earthquakes generate?
Body Waves (P and S) and Surface waves
Define: P waves
Primary, comes first, can travel through both solid and liquids. Fastest
Define: S waves
secondary, can't travel through liquids
Which wave causes the most damage?
Surface waves because of the up/down and side/side motion
How do you determine how far away the earthquake was?
measure the distance between the P and S wave
How do we measure the size of an earthquake?
the max S wave measured on a Richter Scale (Log10 scale)
Define: Modified Mercalli Intensity Scale
Based on touch feely science. "are animals acting funny, did you feel it, was there damage"
What were some major North American Earthquakes?
-San Francisco 1906 (most of the city destroyed. This is when the US started looking into earthquakes) -Alaska 1964. Magnitude 9.2 (largest earthquake in US history)
What were some major world earthquakes
Chile 1960 (mag magnitude 9.5. largest in the world) Turkey 1999 (mag 7.4 killed 17,000 because of poorly built homes) -Sumatra 2004 (mag 9. Tsunami kills 250,000)

Deck Info

55

mimino15

permalink