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Geology Exam 4
Terms in this set (45)
What is a contour line?
a line on a map joining points of equal height above or below sea level.
What are the two differences between INDEX contour lines and "regular" contour lines?
index contour lines-Index contours have their elevation on them. They are found at equal intervals and help you to determine contour interval and elevation. They occur every four or five lines
What type of landform is represented by hachure markson contour lines?
A contour line with hachure marks indicates a topographic high. Close contour lines indicate a steeper slope.
What is the difference between a BENCH MARK and a SPOT ELEVATION?
bench mark- a standard or point of reference against which things may be compared or assessed.
spot elevation- spot elevations are used principally to indicate points higher than their surroundings.
What is the maximum possible elevation rule? What is the minimum possible elevation rule?
max possible elevation- highest part of elevation on a map minus one. ex:(10)(20)(30)=highest so add 10 more =40 minus 1=39!
min possible elevation- lowest part of elevation on a map add 1 ex:(20)(30)(40)= lowest=20 minus 10=10+1=11!
In the context of topography, what is the definition of the term RELIEF?
We could for example use relief to describe the elevation, direction, and angle of slope of a mountain range.
What does the representative fraction tell you about the map?
A representative fraction indicates ratio between the number of units on the map to the number of units on the ground. ... An RF of 1:24,000 means one inch on the map equals 24,000
What does the size of the denominator (the number to the right of the colon in the RF) tell you about the size of the area covered by the map?
1:24,000 means one inch on the map equals 24,000 inches on the ground and one centimeter on the map equals 24,000 centimeters on the ground.
What does the spacing of contour lines tell you about the nature of the slope?
we can state that where the contours are closer together, the slope is steeper.
What is a glacier? What force causes them to move?
A glacier is a large, perennial accumulation of crystalline ice, snow, rock, sediment, and often liquid water that originates on land and moves down slope under the influence of its own weight and gravity
they move by internal deformation of the ice, and by sliding over the rocks and sediments at the base.
What are the two types of glaciers, and how are they different?
Two kinds of glaciers are continental glaciers and valley glaciers.
They are differentbecause a continental glacier covers much of a continent and a valley glacier forms in a mountain valley.
Which type afflicted Michigan during the "Ice Age"?
Continental glacier afflicted michigan during the most recent ice age.
On what landmasses do the two largest glaciers in the world today sit upon
What happens to the glacier in the "Zone of Accumulation"?
The region where snowfall adds ice to the glacier. It occurs where the temperature remains cold enough year-round so that winter snow does not melt or sublimate away entirely during the summer.
What percentage of Michigan was covered by glacial ice during the "Ice Age"?
What happens to the glacier in the "Zone of Wastage"?
The lower part of the glacier is the zone of wastage. The lower edge of the glacier is the terminus. (the end of the glacier.)
By what two methods do glaciers advance?
What is the difference between them?
1) deformation of the ice itself and (2) motion at the glacier base. At the bottom of the glacier, ice can slide over bedrock or shear subglacial sediments.
This means a glacier can flow up hills beneath the ice as long as the ice surface is still sloping downward.
How do glaciers weather the rock over which they flow?
Erosional work of Glacier
Frost Wedging and Impaction.
What two features, found in bedrock, does the ice produce as it moves along?
Glacial Striations and Glacial Polish
How it is deposited,
what it consists of, what it looks like...
Glacial drift composed of an unconsolidated heterogenous mixture of clay, sand, pebbles, cobbles, and boulders.
Describe the 3 different types of moraines: their size, shape, and the type of budget under which eachmoraine forms
Terminal End Moraine-Marks furthest advancing of ice
-Ridged Shaped mass-50 to 200 feet tall
- Half mile to several miles long
Ground Moraine- - Sheet like a body
- Form When Glacier Recedes
Recessional End Moraine- Forms after glacier recedes but then stabilizes
- Ridged shaped body of till
- Roughly same size as Terminal End Moraine
What is an erratic?
What is a drumlin?
Under which glacial budget does a drumlin form?
Boulder size rock plucked from 1 type of bed rock, moved by ice, and deposited on another kind of bed rock
Elongated hill of till formed as the ice overrides previously formed moraines and reshapes the till into drumlins
Describe Outwash: How it is deposited, what is consists of, what it looks like...
Debris carried over away from ice by melting glaciers, mostly sand and gravel. It's carried by rivers but can be all sizes.
What is an Esker? How does one form?
What is a Kame? How does one form?
Worm like ridge of out wash, forms when river deposits out wash within a tunnel under glacier
Mound of outwash. It forms when rivers flow into the moulin carrying outwash, the moulin fills up with the outwash. Ice recedes and leaves the outwash as a pile on the landscape.
How do Kettles and a Kettle Lakes form?
Kettle- Receding glacier leaves behind large blocks of "dead ice". Outwash pours off the glacier and surrounds and buries the dead ice blocks. Ice blocks melt and leave a depression on the outwash surface called Kettle Holes.
Kettle Lakes - If the kettle hole collects water, it becomes a lake.
On what glacial depositional feature (of the 8 you learned about) are kettle lakes found?
Michigan has over 10,500 inland lakes. What kind of lakes are most of these?
If you live in Macomb County, what feature, essentially, are you living upon?
The floor of a now vanished pro-glacial lake
Glacial lake plain
What features help geologists determine the size of ancient pro-glacial lakes?
By mapping the beaches, geologist can determine the size.
covered by ice during the most recent "Ice Age"?
33 percent About 1/3
How did the Great Lakes form?
Formed by weak bedrock eroding and wearing away then filling with water.
Define Mass Wasting
What are the 6 controls on Mass Wasting?
The downslope movement of debris in response to gravity
Thickness of Debris
Orientation Plains of Weakness
How does each of these 6 controls affect Mass Wasting?
1) If steeper, stuff more likely to move
2) If greater, material picks up the speed
3) If thicker=heavier=more likely to move
4) If these are orientated downslope, slabs can slide more easily
5) Excess moisture can saturate debris=weaker/heavier
6) Anchoring effect of plant roots
What drives Mass Wasting?
What roles do the normal force and the shear force play in determining whether or not mass wasting occurs?
Eternal battle=whichever is stronger wins & determines the outcome
What is shear strength?
What factors play a role in determining shear strength?
the gnesiveness of the debris. friction between particles, the plant roots boost the shear strength.
How does the presence of water affect mass wasting?
Water acts like a glue and binds the sediments together.
Describe Creep. What features would you look for to determine if creep has occurred?
Very slow downslope movement of soil, till, outwash.
some water in the debris and living somewhere where there is daily cycle of freeze/thaw. Tilted phone posts/gravestones, shifted railroads
Define Earthflow. What factors play a role in whether or not Earthflow occurs?
downslope movement of the viscous fluid. consist of thick clay, soil, outwash, till
water saturation and thick accumulation of debris.
What features characterize an earthflow?
scarp, hummocky toe, flowing debris, stationary debris,rotated block
Describe the conditions under which Mudflow is most likely to occur.
channelized mix of flowing debris that occupy river valleys
volcanic ash that mixes with water forming a mud.
What is a Debris Avalanche?
What roles do slope angle and relief play in Debris Avalanche?
turbulent mass of rock, soil, ice, trees and anything that gets in the way. the most rapidly moving mass wasting event
steep slop- strong force of gravityhigh relief- enables the debris to build up speed.
Under what conditions is Rockfall most likely to occur?
frost wedging and undercutting
What type of control dominates in Rockslides?
inclined plane of weakness; downslope orientation of planes of weakness in bedrock
In what 6 ways can a mass wasting event be prevented?
How do these methods work?
1)Drain away the excess H20=prevents saturation.
2)Remove the offending materials.
3)Stitch the bedrock-insert steel rods thru the unstable layers into stable layers that are deeper in the mountain.
4) Screen the bedrock=heavy duty fencing covering the unstable areas.
5)Build a sea wall=prevent undercutting of coastal cliffs.
6)Vegetate the area-works well on the loose debris (till, outwash, sand, soil)
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