Term
| Glacier - a thick mass of |
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Definition
| ice that forms over land from the compaction and recrystallization of snow and shows evidence of past or present flow |
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Term
| You see evidence of glacial ice in |
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Definition
| the Alps, Cape Cod, Yosemite Valley, the Great Lakes and in many areas around the world |
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Term
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Definition
Valley, or alpine glaciers
Ice sheets, or continental glaciers
Ice caps and piedmont glaciers |
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Term
| Valley, or alpine glaciers |
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Definition
form in mountainous areas
Generally the width’s of alpine glaciers are small compared to their length |
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Term
| Ice sheets, or continental glaciers |
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Definition
Large scale
Flow in all directions from one or more centers
e.g., Over Greenland and Antarctica
Combined areas represent almost 10% of the Earth’s land area
Ice sheets represent 80% of the world’s ice and nearly two-thirds of the Earth’s fresh water
If ice sheets melted sea level would rise 60-70 m (200-300 ft) and many coastal areas would be inundated |
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Term
| Ice caps and piedmont glaciers |
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Definition
Ice caps cover uplands and plateaus
Iceland and several large islands in the Artic Ocean
Piedmont glaciers occur as broad lowlands at the bases of steep mountains where one or more valley glaciers emerge from the confining walls of mountain valleys |
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Term
| Types of glacial movements |
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Definition
Plastic flow
Slipping along the ground
Glaciers move by basal sliding and internal plastic flow |
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Term
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Definition
the area where a glacier forms
Addition of new snow promotes movement |
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Term
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Definition
| – the area where there is a net loss due to melting |
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Term
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Definition
Calving is where large pieces of ice break off the front of a glacier
Icebergs are glaciers that reach the sea |
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Term
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Definition
| the balance or lack of balance between accumulation at the upper end of a glacier and loss at the lower end |
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Term
| If ice accumulation exceeds ablation |
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Definition
glacial front advances until the two factors balance
At this point the glacier becomes stationary |
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Term
| If warming trend increases ablation and/or if a drop in snowfall decreases accumulation |
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Definition
| , the ice front will decrease |
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Term
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Definition
Plucking – lifting of rock blocks
Abrasion |
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Term
| Plucking – lifting of rock blocks |
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Definition
Occurs when melt water penetrates the cracks and joints along the rock floor of the glacier and freezes
Water freezes and exerts pressure and pries rocks loose |
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Term
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Definition
Rock flour (pulverized rock)
Striations (grooves in the bedrock)
Linear scratches on the bedrock surface provides clues to the direction of glacial movement |
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Term
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Definition
Largely controlled rate of glacial movement
Thickness of the ice
Shape, abundance and hardness of the rock fragments contained in the ice at the base of the glacier
How the surface beneath the glacier erodes |
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Term
| Landforms created by glacial erosion |
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Definition
Glacial trough
V-shaped valleys-widened,deepened,straightened--formed into a U-shaped valley
Hanging valley
main glacier cuts deeper than smaller tributary glaciers
Cirque
Bowl-shaped depression at head of a glacier valley
Arête
Sinuous, sharp-edged ridges
Horn
Sharp pyramid-like peaks
Fiord
Deep, steep-sided inlets of the sea--like Lochness Lake |
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Term
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Definition
| All sediments of glacial origin |
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Term
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Definition
Till – material that is deposited directly by ice Deposited as unsorted mixture of particle sizes
Stratified drift - sediment deposited by meltwater Sorted according to the size and weight of the fragments |
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Term
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Definition
| Moraines – layers or ridges of till |
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Term
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Definition
Lateral
Glacial material left behind after melting that forms ridges along the sides of the valleys
Medial
Are formed when two valley glaciers coalesce to form a single ice stream
End
Gently rolling layer of till deposited as the ice front receeds
Ground
A ridge of till that forms the terminus of a glacier
Forms when the ice is melting near the end of a glacier at a rate equal to the forward advance |
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Term
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Definition
Moraines
Outwash plain or valley train
Kettle
Drumlins
Eskers
Kames |
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Term
| Outwash plain, or valley train |
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Definition
Outwash is melt water emerging from ice loses velocity and much of the bed load is dropped
A stratified drift is built adjacent to the downstream edge of most end moraines
Called outwash plain when associated with an ice sheet
When it is confined to a mountain valley it is usually referred to as a valley train |
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Term
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Definition
Basins or depressions in end moraines, outwash plains and valley plains
Form when blocks of stagnant ice becomes buried in drift and eventually melt, leaving pits in the glacial sediment |
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Term
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Definition
Streamlined, asymmetrical hills composed of till
Believed that drumlins originate when glaciers advance over previously deposited drift and reshape the material |
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Term
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Definition
| Deposits made by streams flowing in tunnels beneath the ice, near the terminus of a glacier |
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Term
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Definition
Steep-sided hills that, like eskers, are composed of sand and gravel
Originate when glacial meltwater washes sediment into openings and depressions in the stagnant washing terminus of a glacier |
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Term
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Definition
Began 2 to 3 million years ago
Division of geological time is called the Pleistocene epoch
Ice covered 30% of Earth's land area |
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Term
| Indirect effects of Ice Age glaciers |
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Definition
Migration of animals and plants
Led to stresses that some organisms could not tolerate
Rebounding upward of the crust
Added weight of 2 mile thick mass of ice caused down warping of Earth’s crust
Worldwide change in sea level
When sea level fell the shoreline shifted seaward
Climatic changes
Temperatures were lower
Precipitation was moderate
Cooler, wetter climate resulted in pluvial lakes
Example – Great Salt Lake |
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Term
Causes of glaciation – not completely understood
Successful theory must account for
Cooling of Earth, as well as
Short-term climatic changes |
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Definition
Proposed possible causes
Plate tectonics |
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Term
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Definition
Proposed possible causes
Plate tectonics
Varitions in Earth's Orbit
Variations in the chemical composition of the atmosphere
Ocean circulation |
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Term
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Definition
Proposed possible causes
Plate tectonics
Continents were arranged differently
Changes in oceanic circulation
Alters the transport of heat and moisture and consequently the climate
Climate change caused by plate movement is extremely gradual and occurs over millions of years
Explains widely space and non periodic onset of glacial conditions |
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Term
Causes of glaciation
Proposed possible causes |
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Definition
Variations in Earth's orbit
Milankovitch hypothesis
Shape (eccentricity) of Earth's orbit varies
Angle of Earth's axis (obliquity) changes
Axis wobbles (precession)
Changes in climate over the past several hundred thousand years are closely associated with variations in Earth's orbit |
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Term
| Variations in the chemical composition of the atmosphere |
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Definition
Ice age atmosphere contained less carbon dioxide and methane than post ice age atmosphere
When the amount of carbon dioxide and methane in the atmosphere increases, the global temperature rises |
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Term
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Definition
Change during an ice age
Warm currents that transfer heat from the tropics towards higher latitudes in the North Atlantic was significantly weaker during the ice age |
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Term
| Geologic processes in arid climates |
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Definition
Weathering
Role of water in arid climates |
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Term
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Definition
Not as effective as in humid regions
Mechanical weathering forms unaltered rock and mineral fragments
Some chemical weathering does occur
Clay forms over long spans of time
Thin soil forms |
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Term
| Role of water in arid climates |
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Definition
Streams are dry most of the time
Desert streams are said to be ephemeral
Flow only during periods of rainfall
Might flow only a few days or few hours during the year
Different names are used for desert streams including wash, arroyo, wadi, donga, and nullah |
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Term
| Role of water in arid climates |
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Definition
Desert rainfall
Rain often occurs as heavy showers
Causes flash floods
Lack of vegetation is key
Poorly integrated drainage
Permanent streams originate outside the desert
Example – the Nile river in Africa
Most erosional work in a desert is done by running water
Different than wind erosion whose main role is transportation and deposition |
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Term
| Basin and Range: the evolution of a desert landscape |
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Definition
Uplifted crustal blocks
Running water begins carving the elevated mass and depositing large quantities of debris in the basin
Interior drainage into basins produces
Alluvial fans and bajadas
Bajadas are an apron of sediment along a mountain front
Playas and playa lakes |
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Term
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Definition
Created by rare abundant rainfall or snow melt from mountains
Flows to the center of the basin
Playa lakes last only a few days or weeks before evaporation and infiltration remove the water
Dry flat lakebed that remains is called a “playa |
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Term
| Basin and Range: the evolution of a desert landscape |
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Definition
Erosion of mountain mass causes local relief to continually diminish
Eventually mountains are reduced to a few large bedrock knobs called inselbergs projecting above a sediment filled basin |
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Term
| Transportation of sediment by wind differs from that of running water in two significant ways |
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Definition
The winds lower density compared to water and renders it less capable of picking up and transporting coarse materials
Because wind is not confined to channels, it can spread sediment over large areas as well as high into the atmosphere |
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Term
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Definition
| Relatively insignificant erosional agent when compared to running water and glaciers |
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Term
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Definition
Lifting of loose material
Because competence of moving air is low it can suspend only find sediment, such as clay and silt
Produces
Blowouts
Desert pavement |
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Term
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Definition
Windblown sand can cut and polish exposed rock surfaces
Limited in vertical extent because sand seldom travels more than 1 m above the surface |
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Term
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Definition
Produces
Blowouts
Shallow depressions
Desert pavement
A stony veneer characterized by a layer of coarse pebbles and cobbles that are too large to be moved by the wind |
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Term
| Types of wind deposits – two distinctive types |
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Definition
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Term
| Types of wind deposits – two distinctive types |
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Definition
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Term
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Definition
Deposits of windblown silt
Extensive blanket deposits
Primary sources are deserts and glacial stratified drift
Most extensive deposits in western and northern China
The fine, buff-colored sediment that gives the Yellow River (Hwang Ho) it’s name
Deposits of loess are significant in South Dakota, Nebraska, Iowa, Missouri, and Illinois |
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Term
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Definition
Mounds and ridges of sand formed from the wind's bed load
If there is a steady significant supply of sand and the wind blows steadily long enough, the mound of sand grows into a dune
Characteristic features
Slip face – the leeward slope of the dune
Cross beds – sloping layers of sand in the dune |
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Term
Sand dunes
Several factors influence the form and size that dunes ultimately assume |
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Definition
Wind direction
Availability of sand
That amount of vegetation present |
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Term
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Definition
Barchan dunes
Traverse dunes
Longitudinal dunes
Parabolic dunes
Star dunes |
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Term
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Definition
Shaped like crescents and with their tips pointing downwind
Form where supplies of sand are limited
Surface is relatively flat, hard, and lacking vegetation
Crescents are symmetrical when the wind direction is nearly constant |
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Term
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Definition
Form in regions where the prevailing winds are steady, sand is plentiful, and vegetation is sparse or absent
Typically are a common coastal dune |
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Term
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Definition
Long ridges of sand that form more or less parallel to the prevailing wind and where sand supplies are moderate
In portions of North Africa, Arabia, and central Australia
These dunes may reach 100m and extend for distances of more than 100 km (62 miles) |
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Term
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Definition
Form when vegetation partially covers the sand
Resemble barchans except that their tips point into the wind rather than downwind |
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Term
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Definition
Confined largely to parts of the Sahara and Arabian deserts
Isolated hills of sand that exhibit a complex form
Form suggests star dunes develop where wind directions are variable |
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