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Exam 2
sed and meta rocks, geo history and petroleum
63
Geology
Undergraduate 2
11/05/2008

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Term
sedimentary rock cycle
Definition
rock-weather down-transport sediment-deposit-lithify-sedimentary rock
Term
mechanical weathering
Definition
physically breaking down rock, produces smaller pieces, and rocks and mineral fragments(clasts)
Term
physical weathering
Definition
rain, streams, wind, thermal stress(expanding and contracting), glaciers, gravity, freeze-thaw cycles
Term
chemical weathering
Definition
involves chemical weathering ex: K-feldspar added to kaolinite clay breaks the rock down
Term
Rock changes as they transport further
Definition
reduction in grain size, increase in sorting, increase in rounding, fine particles travel farther down stream
Term
deposition environments
Definition
continental(valley,edge of glacier,stream, lake, desert), transitional(delta, beach, tidal flats), marine(shallow continental shelf, deep ocean)
Term
clastic rocks
Definition
rocks that form from clasts or rock fragments getting pressed together
Term
chemical sedimentary rocks
Definition
usually form at or near their place of deposition usually from seawater
Term
biological sediments
Definition
form at or near their place of deposition but are the result of mineral precipitation within organisms as they grow. ex: shells or corals
Term
cross bedding
Definition
bedded material deposited by wind or water at angles usually on steep downslopes
Term
mud forms____, sand forms_____, gravel forms _____
Definition
shale, sandstone, conglomerate
Term
carbonate sedimentary rocks
Definition
ex: limestone form in marine environments w/ calcium carbonate(shells). lights helps to foster the growth of carbonate deposits
Term
conglomerate
Definition
forms in river or continental environments where pebbles are gravel are deposited
Term
sandstone
Definition
forms in transitional environments where finer particles settle out once the current slows and cannot suspend sediments anymore
Term
siltstone, shale, mudstone
Definition
usually forms in marine environments or on the edges of the transitional environments where the current ceases to suspend even the finest particles
Term
metamorphic processes that change rocks
Definition
solid state changes that result in rearrangements of atoms (heat, pressure, fluid activity)
Term
heat
Definition
comes from the mantle and the core(leftover heat from the formation of earth) and from radioactive decay
Term
geothermal gradient
Definition
for every km of depth the temperature increases 25-30 deg C
Term
confining pressure
Definition
equal pressure in all directions from layers of rock
Term
differential pressure
Definition
unequal pressure coming more from one direction that from others ex: tectonic pressure
Term
fluid activity
Definition
speeds up metamorphic process, can help atoms throughout the lattice framework of a rock easier to cause rearrangement and metamorphism happen easier
Term
time
Definition
not a process but a major factor in the metamorphism of rocks
Term
contact metamorphism
Definition
comes from a magma pluton metamorphosing the surrounding country rock, may come from hot water convection current
Term
regional metamorphism
Definition
a large area subjected to higher than normal heat/pressure. Usually involves tectonic activity and differential pressure. produces foliated rocks. most common form of metamorphism
Term
grade of metamorphism
Definition
low grade-muscovite, medium grade-biotite,garnet, high grade-partial melt
Term
principles of correlation
Definition
sedimentary layers usually start out horizontally, younger layers always overlie older layers, cross-cutting layers are younger than the affected layers, inclusions are always older than the enclosing rock body
Term
relative dating
Definition
we can date things in relation to each other but not an exact age. use the principles of correlation
Term
absolute dating
Definition
finding the exact numerical age of a rock or fossil by using isotopic dating which uses naturally occurring radioactive elements
Term
half-life
Definition
time required for half of the original atom to decay into the daughter(other type)of atom. doesn't change with temperature, pressure, chemistry or anything else, complications-lose isotopes through weathering or fluids, or metamorphism can reset isotopic composition to younger age
Term
catastrophism
Definition
earth's surface formed in a great cataclysim. sudden violent events, unknowable cause by events not now operating
Term
uniformitarianism
Definition
earth's surface is a product of processes still happening today. processes in the past were the same as today, observed rates of change are slow so earth must be very old
Term
actualism
Definition
uniformity of processes but rates of processes have varied with time. linear history, consequences of long geologic time periods-slow processes have large effect, rare catastrophic events will occur, earth is affected by gradual and catastrophic processes, all changes are a result of natural processes
Term
geologic time
Definition
eon, era, period, epoch
Term
deep time
Definition
geologic time is so long that even rare events have occurred repeatedly
Term
strike
Definition
the compass direction that a rock layer points
Term
dip
Definition
the amount of tilt that the rock layer has from horizontal
Term
dip-slip fault
Definition
movement of the blocks up or down
Term
strike-slip fault
Definition
the movement of the blocks occurs horizontally
Term
normal fault
Definition
a dip-slip fault that occurs from tensional forces that pull rocks apart
Term
reverse fault
Definition
dip-slip fault that occurs from compressive forces that push rocks together
Term
left-lateral fault
Definition
the body on the left moves down
Term
right-lateral fault
Definition
the body on the right moves down
Term
anticlines
Definition
the arches or peaks that occur
Term
synclines
Definition
the troughs or valleys
Term
asymmetrical folds
Definition
when the folds are not perpendicular to the ground
Term
overturned folds
Definition
when the folds are tilted beyond vertical
Term
tensional tectonics
Definition
brittle crusts pull apart and create valleys or depressions like the Rhine River Valley or the Red Sea rift
Term
compressive tectonics
Definition
plates colliding that either produce megafaults(huge earthquakes or tidal waves), or large mountain ranges like the Himalaya
Term
shearing tectonics
Definition
bodies move past each other horizontally, not much internal damage to rocks, San Andreas Fault
Term
petroleum
Definition
mixture of different kinds of hydrocarbons (hydrogen and carbon)
Term
formation of petroleum
Definition
dead marine algae and plankton sinks to bottom, buried, organic rich rock (black shale) pressure and heat (oil-90-160C) forms oil. usually for oil 4-6 km and gas up to 9 km
Term
finding oil deposits
Definition
need a source rock(organic rich shale), reservoir (rock layer that is permeable with space between pores so that fluid can flow through ex: sandstone), trap (tight impermeable rock layer so oil can accumulate)
Term
finding petroleum
Definition
usually accumulates in the anticlines, use seismic exploration to find discontinuity
Term
reserves
Definition
definite supplies, we found them, know they exist
Term
resources
Definition
projected supplies, we hope they are there
Term
peak oil
Definition
rate of oil production will peak and then decline in a symmetrical bell shaped curve developed by Hubbard
Term
problems with breaking with oil
Definition
cheap easy form of energy, most concentrated form of energy we have in abundance and easy access to
Term
demand and price of oil
Definition
tied to supplies, as supplies get tighter, prices becomes more volatile and in general prices go up
Term
coal
Definition
50% of US electricity, cheap and it is very abundant main problem is the environmental impact of coal
Term
formation of coal
Definition
forms from dead plant life (twigs,leaves, etc) in a marshy environment. the higher the temps for formation, the higher the carbon content of coal
Term
mining techniques for coal
Definition
open pit mining- large open holes, coal is removed and then rocks are replaced. contour mining- go around the mountain and strip the coal from the sides of a landscape. mountain top removal- the top of a mountain is removed and put in a valley to get at the coal within the mountain
Term
negative impacts of coal on the environment
Definition
contributor of CO2, acid rain, mercury contamination, and metal contamination. large amounts of ash and sulfer
Term
alternative energy resources
Definition
positives: less of an environmental impact, more sustainable no shortage
negatives: expensive to develop, oil is profitable and quashes other energy sources, disposal and safety (nuclear)
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