STRATIGRAPHY AND SEDIMENTATION (GLACIER) Flashcards
How much of Earth’s and surface is coverd by glacier?
10%
Thick ice mass formed over hundreds or thousands of years
Glacier
Processes in Glacier formation
Accumulation
Compaction
Recyrstallization
Small glaciers which occupy lofty mountains bounded by precipitous rock walls and is a stream of ice that flows downvalley from a snow accumulation center near its head
Valley Glacier
A longer than wide type of valley glacier
alpine Glacier
An example of Valley Glacier in Alaska
Hubbard Glacier,
Yukon Territory
Larger than valley glaciers, enrmous masses flow out in all directions from one or more snow accumulation centers and completely obscure all but the highest areas of the underlying terrain
Ice Sheet
Ice sheet in the northern hemisphere
Greenland
Ice sheet in the southern hemisphere
Antarctica
The date in history that glacial ice covered large portions of N America, Europe and Siberia some 18000 years ago
Last Glacial Maximum
Is Arctic Ocean covered by glacier?
No, it is coverd by Sea Ice which is much thinner than Glaciers
Do glaciers form on water?
No they form on land
Largest Island on Earth sitauted between 60-80 deg N Lat
Greenland
How much of Greenland is covered by ice sheet?
80% or 1.7M sq.KM
What is the thickness of Glacier in Greenlan
1500 m
What is the max thickenss of Antarctic Ice Sheet
4300 m
How much are is covered by Antarctic Ice Sheet
13.9 M sq.km. / 5460000 sq miles
How much area is covered by Ice Shelves in Antarctic
1.4 M sq km / 546000 sq.miles
What is the proper term for Greenland and Antarctic
Continental Ice Sheets
Large, relatively flat masses of floating ice that extend seaward from the coast but remain attached to the land
Ice Shelves
Largest Ice shelves on Earth
Ross and Ronne-Filcher
Type of glacier covering uplans and plateaus which completely bury the underlying landscape but are smaller than conitental-scale feature
Ice caps
Type of glaciers that occupy Broad lowlands at the bases of a steep mountain and form when one ot more valley glaciers emerge from the confining walls of mountain valleys
Piedmont Glacier
Largest piedmont Glacier in Alaska
Malaspina Glacier
Toungues of ice which are valley glaciers which are avenues for ice movement from an ice cap or ice sheet through mountainous terrain to the sea extending outward from the margins of these larger ice masses
Outlet Glacier
Forms of Ice Movement
1) Plastic Flow
2) Basal Slip
At which depth does Ice begin to behave plastically
50 m or 165 feet
This happens when the entire mass of ice slips along the ground
Basal Slip
which portion of the glaciers move slower due to frictional drag?
Lower portion
The uppermost 50 meters portion of a glacier
Zone of Fracture
Gaping cracks in the uppermost part of glaciers caused by tension when glaciers move along irregular terrain
Crevasses
In which part of the glacier is flow the greatest?
at the center
Glacier in Switzerland in which movement of ice has been studied
Rhone Glacier
extreme rapid advance of glaciers
surges
What is the ranking of antarctica based on the size of continents?
5th
The Coldest, Windiest and Highest average elevation
Antarctica
Latitude of Antarctic Circle
66.5 S Lat
Type of climate in which the ave temp of the warmest month is 0 deg celsius or 32 F
Ice Cap Climate
Land formation which separates East from West Antarctica
Transantarctic Mountains
Highest peak in Antarctica
Vinsons Massif
The raw material from which glacial ice originates
Snow
The zone where snow accumulates and ice forms which thickens the glacier and promotes movement
Zone of Accumulation
Outer limits of zone accumulation which is sea level in polar regions and 5000m in places near the equator
Snowline
Zone where there is a net loss to the glacier as snow from the previous winter melts as well as some glacial ice
Zone of Wastage
The process of breaking large pieces of the glacier on its front part which creates Iceberg especially in places where glacier has reached the sea or lake
Calving
how much of icebergs’ mass are submerged in water
more than 80%
The balance or lack of balance between the accumulation at the upper end of the glaicer and loss at the lower part of the glacier
Glacial Budget
When does a glacier is said to be receding?
When forward movement is so slow to offset the rate of wastage
What is plucking?
Meltwater goes into cracks and joints of the rock floor of glaciers and freezes. As it expands, it exerts tremendous presure and breaks the rock
What is Abrasion?
Processes of smoothening the bedrock when the ice loaded with rock fragments slide over it.
The pulverized rock produced by glacial gristmill
Rock Flour
Long scratches and grooves embedded into the bedrock due to abrasion which can denote glacial movement
Glacial Striations
When do glacier produce striations?
When the rock fragments carried by the ice are large
Factors that affect differential erosion by ice
- Rate of Movement
- Thickness of ice
- Qualities of rock containe at the base of the ice
- Erodability of the bedrock
U-shaped valleys formed as glacier widens and deepends them
Glacial Trough
Valleys left by tributary glaciers that are left standing above the trunk glacier or glacier trough
Hanging Valleys
Bowl-shaped valley which have precipitous walls on three sides but are open on the downvalley side and is the focal point of the glacier’s growth because it is situated within the zone of accumulation
Cirque
A lake that usually occupies the cirque basin after the glacier melt away
Tarn
Sinuous sharp-edged ridges formed by glaciers
Aretes
Sharp, pyramidlike peaks formed by glaciers
Horns
Famous Horn in Switzerland
Matterhorn
Deep, often spectacular, steep side inlets of the sea that exists in many high-latitude areas of the world where mountains are adjacent to the ocean forme when the ice melts an the remnant glacial trough was submerged due to sea level rise
Fjords
An all embracing term for sediments of glacial origin no matter how, where, or ,in what form they were deposited
Glacial Drift
A type of glacial drift deposited directly by glacier deposited as ice melts and drops its load of rock debris; Poorly sorted
till
A type of glacial drift deposited by the glacial meltwater that are well sorted according to size and weight
Stratified Drift
Boulders found in the till or lying free on the surface that are unrelated to the bedrock
Glacial erratics
Simply layers or ridges of Till
Moraines
Ridges along the sides of the valley left from the large quantities of debris of valley walls formed by erosion of valley glacier
Lateral moraines
Formed when two valley glaciers coalesce to form a single ice stream thus the till that was formerly on the edges now form a single dark stripe of debri in te middle of the newly enlarged glacier
Medial moraine
a ridge of till that forms at the terminus of a glacier an is formed when a state of equilibrium is attained between wastage and ice accumulation - in a state of quilibrium
End Moraine
Forms when gently rolling layer of till is deposited as the ice front recedes and has leveling effect which usually fills low spots and clogging old stream channels
Ground Moraine
The very first end moraine to form which marks the farthers advance of the glacier
Terminal End Moraine
The end moraines that forms as the ice front occasionally stabilizes during retreat
Recessional End Moraine
A ramplike accumulation of stratified drift found adjacent to the downstream edge of most end moraines and is formed in ice sheets when metlwater loses velocity and drop much of its bedload
Outwash Plain
A ramplike accumulation of stratified drift found adjacent to the downstream edge of most end moraines and is confined in mountain valley when metlwater loses velocity and drop much of its bedload
Valley Train
A pockmarked basins or depressions on end moraines, outwash plains, and valley trains that is formed when a block of stagnant ice was buried in dirft and eventually melt leaving pits with glacial sediment. Usually does not exceed km in diameter
Kettles
Streamlined assymetrical hills compose of till with height range of 15-60m and length of 0.4-0.8 km formed in the zone of flow within an active glacier
Drumlins
clusters of drumlins
Drumlin Field
What directions is denoted by the steep side of the hill?
The direction from which the ice came from
What direction is denoted by the gentle side of the hill?
The diection to which the ice moved
Sinouos ridge of sand and gravel landforms found in places the were once occupied by glaciers an is formed by deposition of stream flowing in tunnels beneath the ice near the terminus of glacier - Stratified Drift
Eskers
Steep-sided hills form when meltwater washes away sediments into openings or depression of stagnatn wasting terminus of a glacier thus when ice melts, the stratified drift is left as mounds or hills
Kames
Other effects of glaciers?
1) Extinction of Ogranisms
2. Crust subsidence and rebound
3. Sea Level Change
4. Change of Drainage Patterns
A bay in canada currently experiencing crustal rebound
Hudson Bay
The largest proglacial lake to form during the Ice Age in North America
Lake Agassiz
Lakes that are relatively small and short lived which are formed as ice sheets and alpine glaciers act as dams trapping glacial meltwater and trapping the flow of rivers. Situated between the ice sheet and sloping land on the other side.
Proglacial Lakes
Whats the implication to sea level when ice sheets increase in size?
Sea Level falls and shoreline moves seawards
Lakes in semi arid and arid environment which were formed due to lower evaporation rates and moderate precipitation rates caused by the presence of glaciers
Pluvial Lakes
This is a pluvial lake formed in North America
Lake Bonneville
Remnant of Lake Bonneville un Utah
Great Salt Lake
This is a complex period characterized by a number of glacial ice advance and withdrawal
Ice Age
Rate of glacial or interglacial cycles
100,000 years
Age of Antarctic Ice Sheet
30 Million Years
Sedimentary rock formed when glacial till becomes lithified
Tillite
how many precambria glacial episodes are there?
2 (2Ga and 600Ma)
Causes of Ice Ages?
1) Plate Tectonics
How does plate tectonics contribute to ice age?
1) The position of the continents
2) Climate Change due to changing positions of continents
What explains the alternation between glacial and interglacial climates?
Milankovitch Hypothesis
Who formulated Milankovitch Cycles?
Milutin Milankovitch
Whats the main premise of Milankovitch Hypthesis?
Earth’s climate is principally controlled by variation in incoming solar radiation
Variations in the shapes of Earths Orbit around the sun
Eccentricity
Change in the angle of Earth’s Axis
Obliquity
Wobbling of Earth’s Axis
Precession
Cycle of change in exccentricity
100,000 years
Cycle of change in obliquity
41,000 years
Current axis of rotation of earth
23.5 degrees
Maximum tilt?
24.5 degrees
Minimum Tilt?
22 degrees
Cycle of Earth’s wobble
26,000 years
current star where the axis points at
North Star
The alternate star in terms of precession
Vega
What is the indication of the increase in CO2 and Methane in the atmosphere
Increase in termperature
Why is sunlight unable to warm the planet during ice age?
Because surface are mostly covered with ice and sunlight or energy is relected back to space
other factors that enable ice age?
1) Decrease in Greenhouse gases
2. Reflectivity of Earth’s Surface
3. Ocean Circulation
