Home > Flashcards > Geology > TEST 1

Details Title: TEST 1 Description: StudyCardsFromPowerPoint Total Flash Cards: 59 Created: 02/14/2007 14:03:57	To study from this set of flash cards, or to create your own your own study flash cards, register HERE. If you are already a registered user, CLICK HERE.
Cards Term Glacier - a thick mass of Definition ice that forms over land from the compaction and recrystallization of snow and shows evidence of past or present flow Term You see evidence of glacial ice in Definition the Alps, Cape Cod, Yosemite Valley, the Great Lakes and in many areas around the world Term Types of glaciers Definition Valley, or alpine glaciers Ice sheets, or continental glaciers Ice caps and piedmont glaciers Term Valley, or alpine glaciers Definition form in mountainous areas Generally the width’s of alpine glaciers are small compared to their length Term Ice sheets, or continental glaciers 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 Term Ice caps and piedmont glaciers 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 Term Types of glacial movements Definition Plastic flow Slipping along the ground Glaciers move by basal sliding and internal plastic flow Term Zone of accumulation Definition the area where a glacier forms Addition of new snow promotes movement Term Zone of wastage Definition – the area where there is a net loss due to melting Term Wasting Definition Calving is where large pieces of ice break off the front of a glacier Icebergs are glaciers that reach the sea Term Glacial budget is Definition the balance or lack of balance between accumulation at the upper end of a glacier and loss at the lower end Term If ice accumulation exceeds ablation Definition glacial front advances until the two factors balance At this point the glacier becomes stationary Term If warming trend increases ablation and/or if a drop in snowfall decreases accumulation Definition , the ice front will decrease Term Glaciers erode by Definition Plucking – lifting of rock blocks Abrasion Term Plucking – lifting of rock blocks 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 Term Abrasion Definition Rock flour (pulverized rock) Striations (grooves in the bedrock) Linear scratches on the bedrock surface provides clues to the direction of glacial movement Term Rates of erosion 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 Term Landforms created by glacial erosion 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 Aręte Sinuous, sharp-edged ridges Horn Sharp pyramid-like peaks Fiord Deep, steep-sided inlets of the sea--like Lochness Lake Term Glacial drift Definition All sediments of glacial origin Term Types of glacial drift 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 Term Depositional features Definition Moraines – layers or ridges of till Term Types of moraines 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 Term Depositional features Definition Moraines Outwash plain or valley train Kettle Drumlins Eskers Kames Term Outwash plain, or valley train 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 Term Kettles 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 Term Drumlins Definition Streamlined, asymmetrical hills composed of till Believed that drumlins originate when glaciers advance over previously deposited drift and reshape the material Term Eskers Definition Deposits made by streams flowing in tunnels beneath the ice, near the terminus of a glacier Term Kames 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 Term Ice Age 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 Term Indirect effects of Ice Age glaciers 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 Term Causes of glaciation – not completely understood Successful theory must account for Cooling of Earth, as well as Short-term climatic changes Definition Proposed possible causes Plate tectonics Term Causes of glaciation Definition Proposed possible causes Plate tectonics Varitions in Earth's Orbit Variations in the chemical composition of the atmosphere Ocean circulation Term Causes of glaciation 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 Term Causes of glaciation Proposed possible causes 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 Term Variations in the chemical composition of the atmosphere 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 Term Ocean circulation 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 Term Geologic processes in arid climates Definition Weathering Role of water in arid climates Term Weathering 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 Term Role of water in arid climates 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 Term Role of water in arid climates 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 Term Basin and Range: the evolution of a desert landscape 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 Term Playas and playa lakes 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 Term Basin and Range: the evolution of a desert landscape 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 Term Transportation of sediment by wind differs from that of running water in two significant ways 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 Term Wind erosion Definition Relatively insignificant erosional agent when compared to running water and glaciers Term Deflation 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 Term Abrasion 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 Term Wind erosion 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 Term Types of wind deposits – two distinctive types Definition Loess Term Types of wind deposits – two distinctive types Definition Loess Sand Dunes Term Loess 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 Term Sand dunes 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 Term Sand dunes Several factors influence the form and size that dunes ultimately assume Definition Wind direction Availability of sand That amount of vegetation present Term Types of sand dunes Definition Barchan dunes Traverse dunes Longitudinal dunes Parabolic dunes Star dunes Term Barchan dunes 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 Term Transverse dunes 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 Term Longitudinal dunes 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) Term Parabolic dunes Definition Form when vegetation partially covers the sand Resemble barchans except that their tips point into the wind rather than downwind Term Star dunes 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