GC100 Exam 4

Geography
eruption
ejection of magma to surface
may be explosive or quiet (effusive)
vent
small pipe leading from magma to surface
bombs
large (up to several tons)
cinders
fraction of inch to about 2 inches
ash
smaller, falls like snow within few miles
dust
may remain in atmosphere for years
cinder cone
explosive
formed by pieces of solidifies lava thrown from central vent
very rapid growth to large central crater with one side higher than the other
cones usually occur in groups, often along a fault
fragments resemble furnace clinker
Composite (strato-) volcano
explosive
alternating layers of cinder/ash and lava flows
heights can reach several thous. feet
crater may change form rapidly, even develop secondary cones
Lava Dome
somewhat effusive/ highly explosive
lava is viscous, sets up quickly (thus producing explosions)
Shield Volcano
effusive
highly fluid lava, spreads before set-up
therefore, gently rising
wide, steep-sided central depression
Lava Plateau
effusive
non-viscous lava flows from fissures
forms horizontal strata, or flows down slope
successive flows may produce deposits thousands of feet thick.
Mineral
natturally occuring inorganic substance
composed of elements forming a crystalline solid
this solid has definite chemical composition and distinctive physical properties
rock
made up of different combinations of minerals
magma
molten rock within the lithosphere which cools to become a solid
lava
molten rock that has reached the surface
crystal characteristics
determined by:
magma chemistry
cooling rate
size of the intrusion
Petrology
the study of rocks
Igneous rocks
formed by the cooling of molten rock
Extrusive Igneous rocks
volcanic rocks which reach the surface
i.e. lava
Intrusive Igneous Rocks
formed by magma which doesn’t reach the surface, but is intruded into crustal rock where it cools
Extrusive Landforms
volcanos and lava flows
Neck
intrusive landform
remnant of solidified lava in the vent of a volcano
dike
intrusive landform
lava “wall” which originally filled a fracture
sill
a horizontal structure, parallel to and interbedded in pre-existing rock
batholith
large body of igneous rock
laccolith
smaller body of igneous rock
Sedimentary rocks
rocks undergo weathering
the particles which are transported and deposited are sediments
the agents of transportation are water, ice, and wind
lithification
the process whereby sediments become sedimentary rocks
detrital
sedimentary rock derived from the remains of preexisting rocks that have been eroded
all are clastic (made up of elements)
Chemical
the result of precipitation of material dissolved in water
folding
the irreversible deformation which rock undergoes due to tectonic stress
folds
resemble wraps of wrinkles in rock
occur in every shape, size

monocline, anticline, syncline, overturned

Metamorphic rocks
either igneous or sedimentary rocks can change in appearance and/or composition. Caused by intense heat or pressure changes in earths crust
contact metamorphism
affects a narrow band of rock surrounding an igneous intrusion
regional metamorphism
causes widespread changes in buried rocks
Weathering
combined action of all processes where rock is decomposed and or disintegrated at or near the earth surface
mass weathering
combined effect of gravity and the forces of weathering
granular disintegration
rock falls apart grain by grain
exfoliation
surface peeling of rock layers
the effect of mechanical and/or chemical weathering or unloading
joint-block seperation
breakage along fractures and bedding joints already there from cooling of magma, crustal movement, and sedimentary processes
shattering
disintegration along new surfaces of breakage in otherwise massive, strong rock
forms very angular pieves with sharp corners and edges
Chemical weathering
hydration
carbonation
oxidation
physical weathering
freeze-thaw heaving
unloading
salt crystals
biological weathering
plants
lichens
animals
Fall
Mass weathering
includes rock fall and debris fall
gravity vs cliff
forms a talus slope
slump
shearing of material along an arced line of slippage
the slump block has a rotational movement and often remains intact
slide
often caused by water entering the rock/soil structure, resulting in a loss of surface tension and added weight
flow
the matter in a slope becomes saturated and results in slope falure.
debris flow and mud flow
creep
due to freeze that activity in the soil

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