Shared Flashcard Set

Details

Geology: The Physical Earth
Plate Tectonics, Streams, Glaciers
84
Geology
Undergraduate 1
05/14/2011

Additional Geology Flashcards

 


 

Cards

Term
Geosynclinal theory
Definition
a big hole fills with sediments and would finall shoot up after pressure was released. Places where mountains are now used to be big holes (geosynclines)
Term
Who proposed Pagaea?
Definition
Alfred Wegner
Term
Give 4 reasons/evidence for continental drift theory.
Definition
1. Africa's and South America's continental shelves fit well geographically
2.continuation of structural trends between continents now separated by ocean basins
3. identical fossils are found on continents that are no longer near eachother
4.paleoclimactic similarities between continents now fair apart (glacial deposits)
Term
What two technological improvements/more comprehensive data collection led to plate tectonic theory?
Definition
1. detailed maps of the sea floor (mid ocean ridges, trenches, fracture zones) result of sonar invention
2. comprehensive sea floor and continental magnetometer surveys.
Term
At what temperature must iron bearing rocks cool below to lock in the ambient magnetic field?
Definition
580 degrees C
Term
What does a magnetometer measure?
Definition
measures strength and polarity of magentic fields. Can find landimines.
Term
What is apparent polar wander and how does it help prove plate tectonics?
Definition
Rocks don't point in the same directions for poles, rocks couldn't have moved. Apparent polar wander is the change in the apparent north pole according to the rocks in various places. shows polar wander and polar wander does not match in rocks until the US and Europe are fit back together.
Term
What did the Ocean Drilling Project conclude about deep ocean floors?
Definition
1. 100% basalt
2. age increases w/ distance from mid-ocean ridges
3. sediment thickness increases with distance from ridges
4. age of oldest sediment increases with distance from mid ocean ridges
Term
What do the magnetometer readings of the ocean floor near MOR's show?
Definition
Some show a magnetic field less than the one we experience today while others show a magnetic field greater than the one we experience today. These are formed into bands parallel to MORs.
Term
Who is responsible for the sea floor spreading theory, what exactly did they propose?
Definition
Vine and Matthews. Sea floor is created at MORs and spreads. Hot asthenosphere rises beneath MORs, decompresses while cooling, splits apart and spreads.
Term
What is the oldest oceanic crust?
Definition
200 million years old
Term
What are guyots? Where do they form?
Definition
a fully submerged former island that formed over a hot spot. It rides on the piece of oceanic crust it formed on and it rides that piece of oceanic crust deeper and deeper, as the sea floor slopes away from MORs. Eventually it is submerged and no longer above the hot spot.
Term
What drives plate tectonics?
Definition
convection resulting from a loss of heat from the interior of the earth that originates from radioactive decay
Term
What is "trench pull"
Definition
the fastest moving tectonic plates are those with trenches
Term
What does the wilson cycle describe?
Definition
Presented by J. Tuzo Wilson, it describes the life cccle of supercontinents and ocean basins. Beginning with one supercontinent 3 prong rift systems break out above hot spots that build up. These begin pumping out basalt pushing the continents apart, resulting in cracks that begin to link up the 3 prong rift systems. Some rifts die and others turn into spreading ridges driving the pieces of the supercontinent apart. They eventually run into eachother again and build up.
Term
Why does the wilson cycle use "3 prong rift systems"?
Definition
Because basalt cools hexagonally
Term
Why are mountains high?
Definition
Due to isostasy. Elevations on earth are a result of the variation of desity and layer thickness of the lithosphere floating on the asthenosphere.
Term
What is pratt isostasy and what is airy isostasy?
Definition
figure it out. . .
Term
What is mass wasting?
Definition
the downward slope movement of rock due to GRAVITY. GRAVITY IS INVOLVED. ALWAYS.
Term
What is the angle of repose?
Definition
the maximum angle a slope is stable it (where mass wasting will stop occurring). gravity, slope and friction govern it
Term
What are 3 ways to initiate slope failure?
Definition
make the angle steeper, earthquake, add water(heavier and a lubricant)
Term
How is mass wasting classified?
Definition
by type of material and type of motion
Term
What are 4 types of material involved in mass wasting?
Definition
rock, mud, debris, earth
Term
What are 4 types of motion involved in mass wasting?
Definition
slide(moves as a coherent block), avalanche(particles suspended in air behaving like fluid due to great deal of energy), flow(moves as a vicous fluid), fall (free fall)
Term
Is a rock slide possible?
Definition
yes a block of rock can slide down an incline plane (mt. st. helens)
Term
Is a mudslide possible?
Definition
Mud cannot move as a "coherent block". it flows. . .
Term
Is a mud avalanche possible?
Definition
No, mud cannot become a free flowing fluid, instead it will always be a viscous fluid.
Term
What type of mass wasting has the lowest rate of motion?
Definition
creep
Term
What is slump?
Definition
the downward sliding of rock or unconsolidated material along a curved plane of failure
Term
What occurs with permafrost in the summer time?
Definition
The top layer becomes liquidy and warm and slides down the frozen lower layer.
Term
What governs the velocity of streams?
Definition
the gradient(vertical drop over a fixed distance), channel shape/size, the amount of water (discharge)
Term
What is discharge defined by?
Definition
cubic meters/second
Term
What is base level?
Definition
the lowest elevation a stream can erode its channel. There are local base levels and ultimate base level (sea level)
Term
What does raising base level for a stream promote?
Definition
deposition
Term
What is a graded stream?
Definition
A stream has eroded to near its base levl. No erosion and no deposition is occuring in the stream. It becomes a sediment conveyor.
Term
What are the 3 ways a stream erodes?
Definition
Abrasion-suspended particles hit sides of channel
Lifting-unconsolidated particles are lifted from the bottom
Solution-dissolves ions into solution
Term
What effects the settling out of carried particles?
Definition
chemical composition change may force material out os solution
a lowering of velocity allows particles to settle out according to settling velocity
Term
What is point boar?
Definition
deposition occurring on inside of bends in stream where the current is slower
Term
Give 5 characteristics of youthful streams
Definition
actively cutting downward
few meanders
narrow, constricted valley, V-shaped
energy is directed downward
found in mountains and include rapids and waterfalls
Term
Give 3 characteristics of mature streams.
Definition
a flood plain has developed
meander belt is same size as flood plain and is actively widening
energy is directed side to side, results in meanders
Term
Give 4 characteristics of old age streams.
Definition
nearing base level-->no deposition/erosion
flood plain is several times wider than meander belt
little directional energy
reworks and moves sediments
Term
How can streams be rejuvenated?
Definition
by raising ground or lowering base level
---results in down cutting and entrenched meanders
Term
Where do you find braiding streams and what characterizes them?
Definition
They have crisscrossed channels as the sediment supply exceeds carrying capacity of the stream. found near glaciers or in the desert
Term
What is occurring in new orleans that will result in it sinking lower and lower?
Definition
It is cut off from receiving the deposits from flooding and the entire area is sinking into the ocean so it is falling beneath sea level
Term
What is an alluvial fan?
Definition
As a stream leaves the mountains it fans out and slows down, deposition sediment in the valley.
Term
What is a delta?
Definition
As a stream enters base level, ex. the ocean, it looses velocity and deposits a great deal of sediment blocking it over and over resulting it fanning out quite a bit.
Term
What is a dentritic network characteristic of?
Definition
unifrom errodability of the bedrock
Term
What is a trellis drainage characteristic of?
Definition
fold belts
Term
What is rectangular drainage controlled by?
Definition
jointing and water flowing through joints.
Term
What melted resulting in the Missoula Floods?
Definition
Cordilleron Ice Sheet.
Term
What is an antecedent stream?
Definition
A stream that flowed before topography was created. Results in downcutting as the topography goes up and creates a water gap. (wallula gap)
Term
What is a wind gap?
Definition
A result of an anticline rising faster than a stream could downcut and eventually diverting the stream.
Term
What do you call a stream that has a dentritic drainage network over folded strata?
Definition
a superposed stream
Term
What kind of stream network do folded strata usually encourage?
Definition
a trellis network
Term
What is a glacier?
Definition
a thick ice mass that originates on land from an accumulation, compaction and recrystallization of snow and shows evidence of past or present movement
Term
What happens when snowfall in the winter exceeds summer melting?
Definition
glacial ice is formed!
Term
What is the zone of accumulation on a glacier?
Definition
where the snow falls and is snowy. moves around during the year
Term
Where is the zone of oblation on a glacier?
Definition
where it is melting and the glacier is bare ice
Term
What is the Firn line?
Definition
Separates the 2 zones.
Term
Where does ice form on glaciers?
Definition
In the zone of accumulation
Term
What is base level for glaciers?
Definition
Below sea level! Unique to each glacier
Term
What are fjords?
Definition
valleys where a glacier had previously met the ocean and melted in its entirety
Term
Valley glacier
Definition
sterams of ice borderd by moutains
Term
Ice sheets
Definition
flow out in all directs from center of accumulation and bury all but the highest mountains. HUGE
Term
Ice shelf
Definition
floating extension of an ice sheet
Term
Ice caps
Definition
small scale ice sheets found in high latitude mountains
Term
Outlet glaciers
Definition
valley glaciers that drain ice caps and sheets
Term
Piedmont glaciers
Definition
tributary valley glaciers that form into one at the foot of mountains
Term
glacial erosion
Definition
fundamentally limits mountain heights with its great erosive power
Term
what controlls the rate of erosion of a glacier?
Definition
thickness of ice
rate of movement
shape, size and abundance of rock fragments
erodability of the substrate
Term
What two mechanisms do glaciers use to erode?
Definition
Plucking-incorporation rock into ice via frost wedging
Abrasion- ice with embedded rock grinds over the bedrock creating rock flour
Term
Which type of glacier subdues the landscape?
Definition
ice sheets and caps
Term
which type of glacier accentuates the landscape?
Definition
valley glaciers
Term
Hanging valleys
Definition
created by the main glacier downcuting faster than tributary glaciers
Term
glacial valley
Definition
U shaped, broad deep and straight
Term
Pater Noster Lakes
Definition
cyclopean steps between lakes, lakes like beads on a string that step down a level with each one
Term
Cirque
Definition
bowl shpaed valley at the head of a glacier trough
Term
Cirque headwall
Definition
back wall of cirque. formed by plucking
Term
Tarn
Definition
lake on the floor of a cirque
Term
arĂȘte
Definition
a high ridge separated glaciers
Term
col
Definition
lo spot on an arĂȘte, a high pass where 2 cirques meet
Term
horn
Definition
an isolated peak produced by the enlargement of cirques
Term
rouche moutanee
Definition
(back of a sheep) bedrock outcrops having polished gently-sloping sides that face up the glacier with steep sides facing down
Term
What is the ocean floor made of?
Definition
From top to bottom: pillow basalts, sheet dikes, gabros and below moho ultramafic rocks
Supporting users have an ad free experience!