Second Test Flashcards
Thicker Crust ______ .
Rises
What happens to subduction zones in continental collisions?
The continent eventually clogs up the subduction zone. It is not dense enough to sink into the mantle. This results in a double thickness of the crust.
Warmer crust is ______ which means it rises.
Less dense
Rift valleys centers are made of ______ and hot crust, while the edges of the valley are _______ and hot
thin ; thick
What does stretching do?
Creates a series of crustal blocks separated by normal faults.
Brittle rock does water?
Fractures in the cool upper crust.
What does ductile rock do?
Flows in the warm lower crust.
What is a joint?
A simple crack that is slightly open- small amount of stress.
What is a fault?
Crack along which two bodies have moved. Larger amount of stress.
Are joints parallel or perpendicular to tension?
Perpendicular
Rock is parallel or perpendicular to pressure?
perpendicular to smallest pressure direction and parallel to greater pressure direction
Tension produces ____ fault motion.
normal
Compression produces _____ fault motion.
Reverse
Strike slip faults are produced by _______ stress at transform fault boudaries.
shear
Sedimentary rock layers often _____ when compressed.
Fold
What is an upward folded layer of rock called
anticline
what is a downward folding layer of rock called
syncline
Fold and thrust belts are common during what
continental collision (compression)
what process creates a metamorphic rock
pressure cooking
Metamorphic rocks formed under _______ develop new fabrics.
uneven stress
Define cleavage
a set of weak plains developed perpindicular to weak compression
define foliation
an alignment of parallel grains developed at higher levels of shear and compression
define lineation
growth of elongated mineral crystals
low pressure, high temperature rock process
contact metamorphicism
blue crystals grow in this type of metamorphism
blueschist metamorphism
what are 3 types of weathering processes
temperature change (expand and contract) oxygen (breaks apart during oxidation) , water (disolves away minerals)
physical weathering
anything that breaks rock into pieces (pressure, exfoliation, tree roots)
rock and soil are pushed down a slope (component)
shear
pushing against the slope by gravity (component)
normal
Define friction
opposes movement along a slope
Causes of landslides
rain, earthquakes, excavation, deforestation
three types of rock movements in a landslide
flow, slide, fall
rock/debris fall
free fall from a cliff, steep slopes
pile of broken rock
talus slope
rock/debris slide
slide along a plane of weakness
rock/debris slump
movement along a curved plane in a hillslope
creep
very slow landslide
rock and debris flows
water saturated masses flowing down a hillside
rock and debris avalanches
high speed flows down mountainsides
chemical weathering
rock materials react with water and oxygen
what is the main mover of sediment
water
three types of sediment loads
bed load, dissolved load, suspended load
bed load
largest pieces bounce and roll across bottom
suspended load
smaller pieces float in current
dissolved load
chemicals dissolved by water during weathering
morraines
sediment deposits carried by glacier movement/melting
what is discharge
volume of water moving past a point on a river
graph displaying discharge over time
hydrograph
drainage divide
high grounds that separate drainage basins
drainage basin
the land area where drainage flows into one river or stream
flash flood
rapidly rising and falling flood event
what creates a waterfall
sharp changes in elevation and rock hardness
alluvial fans
form in desserts at the mouth of canyons
slope of a river
gradient
braided rivers
formed by fast moving water and sediment from spring snowmelt. As water level drops off rivers become choked off from sediment and break into crisscrossing channels (moderately steep gradient, fast water flow)
meandering rivers
occur in flat, lowland areas away from mountains, single looping channel, light colored areas equal fresh sediment
describe channel migration
meandering rivers erode sediment from the outide of a loop (cutback) and deposit sediment on the inside of a loop (pointbar). over time this causes the channel to migrate across the floodplain, leaving an abandoned channel called an oxbow lake
what is a levee
low mounds of sediment next to a river channel, formed during flooding. coarse sediment piles up next to a channel while fine sediment spreads out on a floodplane
delta
formed when rivers deposit sediment upon entering the ocean. multiple channels in deltas called distributaries are then formed
describe how sediment changes as it goes downstream
river valleys are steepest at headwaters- this is where most erosion occurs. as sediment pieces are carried downstream they are gradually weathered and broken down
discharge
width X depth X water speed
