GEOG 2030 Quiz 2

drivers of glacial movements

(1) deformation at the glacier bed 2 deformation at the ice-front (bull-dozing) producing folds, thrusts, and nappes (ice-thrust ridges and push-moraines) 3 Dead-ice tectonics associated with collapse, till debris flow, and crevasse infilling (so-called dead-ice morainal plateaux and other features.

ephermal stream

:a stream that flows only briefly during and following a period of rainfall in the immediate locality.

slipface

:the lee side of a dune where the slope approximates the angle of rest of loose sand that is generally about 33 degrees.

accumlation zone

Is the area of the glacier that is building up, has three major layers. The top layer is seasonal snow that thickens further up glacier. The next layer is the "firn", or a transitional form between the snow and solid ice below. The bottom layer is ice.

turbidity currents

a rapid, downhill flow of water caused by increased density due to high amounts of sediment. Can be set into motion when mud and sand on the continental shelf are loosened by earthquakes, collapsing slopes, and other geological disturbances.

torrent

a strong and fast-moving stream of water or other liquid.

throughflow

a subcomponent of interflow, is the lateral unsaturated flow of water in the soil zone, where a highly permeable geologic unit overlays a less permeable geologic unit, and which returns to the surface, as return flow, prior to entering a stream or groundwate

Sheetwash

a thin, mobile sheet of water flows over the surface of a hill-slope and may transport the surface regolith. It is important in semi-arid regions, and may also be significant in temperate zones if the vegetation cover has been removed.

craig and tail forms

a type of drumlin that forms behind a projecting rock knob

Jokhulaups

a type of glacial outburst flood.

terminal moraine

a type of moraine that forms at the snout (edge) of a glacier, marking its maximum advance. At this point, debris that has accumulated by plucking and abrasion, and has been pushed by the front edge of the ice, is driven no further and instead is dumped in a heap. Because the glacier acts very much like a conveyor belt, the longer it stays in one place, the greater the amount of material that will be deposited. The moraine is left as the marking point of the terminal extent of the ice

hanging valley

a valley that is cut across by a deeper valley or a cliff

Glacial lake Agassiz

a very large glacial lake located in the middle of the northern part of North America. Fed by glacial meltwater at the end of the last glacial period, its area was larger than all of the modern Great Lakes combined[1] though its mean depth was not as great as that of many major lakes today.

hypsithermal

a warm period during roughly the interval 9,000 to 5,000 years BP. It is a very major dry period, dune activity, and absence of buffalo in some of the drier regions of the prairies, and thus no artifacts.

Gulleys

a water-worn ravine.

tranverse dune

abundant and steady build-up of sand supply, so fairly uniform winds

tunnel valleys

are very large channels cut into bedrock (Nye channels) and may contain eskers, have undulating longitudinal profiles and may have lake basins along their floor. They often become completely filled with sediment later on. They are often oriented obliquely to the modern drainage system, telling us that they were formed from waters that were under pressure (hydrostatic head in ice body).

Hallet

argues that ice thickness does not have a bearing on stresses differences at the abrasive bed contact area, but is the product of viscous drag induced by ice flow towards the bed, aided by basal melting and longitudinal extension of the ice

Lyell and Dawson

believed that marine submergence and icebergs were responsible features suchs as erractics and roche moutonees

absent of permafrost

beneath glaciers, icecaps, lakes, and rivers, deltas. This makes river crossing particularly difficult for pipeline engineering in northern latitudes. -On Baffin Island and Ellesmere Islands, as well as Islands off the Yukon and MacKenzie Delta, it may be as much as 1000 meters deep—again suggesting fewer or no major Pleistocene ice-sheets covered those areas.

Medieval warm period

, brief climatic interval that is hypothesized to have occurred from approximately 900 ce to 1300 (roughly coinciding with the Middle Ages in Europe), in which relatively warm conditions are said to have prevailed in various parts of the world, though predominantly in the Northern Hemisphere from Greenland eastward through Europe and parts of Asia.

Little ice age

, climate interval that occurred from the early 14th century through the mid-19th century, when mountain glaciers expanded at several locations, including the European Alps, New Zealand, Alaska, and the southern Andes, and mean annual temperatures across the Northern Hemisphere declined by 0.6 °C (1.1 °F) relative to the average temperature between 1000 and 2000 ce

Atterburg limits

a basic measure of the critical water contents of a fine-grained soil: its shrinkage limit, plastic limit, and liquid limit. As a dry, clayey soil takes on increasing amounts of water, it undergoes distinct changes in behavior and consistency.

whaleback

a bedrock knoll smoothed and rounded on all sides by a glacier

Erg desert

a broad, flat area of desert covered with wind-swept sand with little or no vegetative cover.The term takes its name from the Arabic word ʿarq , meaning "dune field".Strictly speaking, an erg is defined as a desert area that contains more than 125 km2 (48 sq mi) of aeolian or wind-blown sand[3] and where sand covers more than 20% of the surface.

quick clays

a clay where the undisturbed shear strength of the soil is at least 30 times greater than the remolded (or disturbed) shear strength.

desert varnish

a dark coating, typically iron or magnesium, or silca that may have become attached to a pebble when clay became attached to the pebble during a storm that was accompanyed by some moisture,. In other cases the secondary oxides result from the weathering (sweating) of the pebble itself.

crevasse

a deep open crack, especially one in a glacie

Reg desert

a desert surface covered with closely packed, interlocking angular or rounded rock fragments of pebble and cobble size. They typically top alluvial fans

Lahar

a destructive mudflow on the slopes of a volcano.

Rills

a small stream.

hummocky moraine

formed by stagnant ice, often with abundant lake.(undrained depressions some of which may be ice-walled) ice block depressions may occur..Often associated with melt-water channels someof which may be ice walled, markedby changes in depressions

dirt layers

formed during summer ablation, or denser ice layers formed during summer melting, can be used to count annual accumulations in an ice sheet.

rat-tail forms

glacial erosion features that form underneath a glacier by vast, fast flowing rivers of glacial meltwater actually eroding the rocks and forming these streamlined features. The dominant bedrock in the area is a soft marble that contains xenoliths of hard Grenville gneiss. The gneiss acts as a barrier to the meltwater forcing it to flow around it. This protects the marble directly behind the xenolith and forms it

driving forces of glaciers

Glaciers flow because of gravitationally induced stresses setup within the ice. Compressive stress results because of the weight of overlying ice and can be divided into hydrostatic pressure (weight of overlying ice) exerted in all directions, and shear stress which results from weight of ice on a sloping surface. Ice crystals deform under stress and slide along crystal planes. They are polycrystalline (composed of many sizes and shapes of crystals), so it takes considerable stress for this to take place. -A plastic body (such as ice) does not deform until it has reached the "yield stress", after which it deforms in almost limitless fashion and does not recover to any original shape after the stress is removed. It is the continuous deformation that allows glaciers to creep or flow under their own weight. The strain rates in ice are effected by temperature, crystal orientation, impurities in the ice, confining pressure, and rock debris carried within the ice. Small increases in any of these can quickly change the stress field in the ice. -If only low stress is applied to ice it behaves as an elastic and rebounds to the original shape when stressed is removed. These two descriptions of how ice behaves are overly simplistic but will suffice for now

ice streams

Greenland, and Antarctica, (and the Laurentide ice sheets of the past) contain zones of much faster flowing ice (10's km wide and 100's kms long) that can be fed by very long up ice tributaries. Because they involve very large quantities of ice they critically control mass balance and stability of ice sheets. Ongoing research on paleo ice streams of the Laurentide suggest that they occurred in topographic lows (Thelon basin, James Bay and Hudson Bay areas) and in areas of deformable sediments (the western Arctic lowlands , Canadian Prairies). Essentially any cascading system might trigger ice stream development.

stakes

are used to measure lowering of surface of ice by ablation, and rate of movement forward (using GPS and total station measurements, or satellite measurements for coarser measurements over larger areas.

supraglacial stream

(flowing on the ice) can be very large, and water may move turbulently (forming meanders) or as sheets of water. But before long these streams disappear into crevasses or holes (moulins) in the ice and this accounts for season or permanent water tables within the ice. The water descends to the base over relatively short span of time and space. Conduits in ice do not last long and are therefore not very dendritic (branching). Water emerges from the snout of the glacier, in cavernous tunnels, and discharge has a strong diurnal variability.

firn

(snow that has survived one summer) is composed of randomly oriented ice crystals. After several more years,it is metamorphosed to ice through recrystalization (many cycles of melting and refreezing) under stress (weight of snow acting on a sloping surface), and results in slow elimination of gases. Can happen in a few years in temperate climates under just a few metres of snow. But in very cold climates may take several thousand years and hundreds of metres of snow accumulation (Greenland and Antarctica).

thaw-flow slides

(thawing of ice-rich sediments) are very common in the Canadian north. They leave a bowl-shaped depression at the head of the flow and have gently sloping terminal tonques or lobes. They resemble earthflows of temperate climates.

rock drumlins

A feature similar to roches moutonnées, they are bedrock knobs or hills completely streamlined, usually with steep stoss sides and gently sloping lee sides. Both roches moutonnées and rock drumlins range in length from several metres to several kilometres and in height from tens of centimetres to hundreds of metres. They are typical of both valley and continental glaciers. The larger ones, however, are restricted to areas of continental glaciation.

esker

A long narrow ridge, often sinuous, composed of stratified sediment and marking the former location of a glacial tunnel.

moraine plateaux

A relatively flat area within a hummocky moraine, generally at the same elevation as, or a little higher than, the summits of surrounding knobs.

Ancient Ice ages

Abundant evidence of ancient glaciations in Canada, Southern Africa, and South America. The Neoproterzoic (850-800 Ma) glaciation may have covered all of earth (Snowball Earth Hypothesis).

Late cenozoic glaciations

Antarctica first with initial buildup around 38 Ma and was completely covered by 25-20 Ma; southern Greenland and Alaska Coastal Mtns were next during Miocene around 10-6 Ma; then Northern Greenland around 3.5-3.0 Ma. Patagonian Cordillera around 3.5 Ma and Yukon and Alaska around 3.0-2.6 Ma. First buildup of major continental ice masses in Canada and Europe were between 2.6-1.0 Ma. With western Canada and most of Europe first receiving a major ice cover around 800 ka.

cold-based glacier

Are frozen to the bedrock all year round as the temperature of the ice stays at zero degrees constantly Tend to move via internal deformation as there is no water for basal sliding to occur Move slowly- causing less erosion to occur Found at high latitudes Examples of cold-based glaciers are the Antarctic and Greenland ice sheets

warm-based glacier

Are not frozen to the bedrock all year round The temperature of these glaciers is not constantly below freezing so water exists within the ice The water acts as a lubricant so basal sliding can occur As basal sliding can occur, warm based glaciers have a faster rate of movement than cold based glaciers and so carry out more erosion They tend to be found at lower latitudes Examples include glaciers found in mountain ranges such as the Alps

percolation zone

Below any dry snow zone (if there is one at all) is one of these (superimposed ice) where daytime melting occurs, and latent heat is released with refreezing at night. Melting can proceed to the base of the annual snow layer (soaked zone) and so this percolation zone is composed of layers of ice, and snow. Lower down most of the annual snowfall melts and refreezes, and merges with the continuous ice mass of the glacier (all this above the E.L.).

Heinrich events

Periods of ice rafting

humid temperature slopes

Slopes are usually convexo-concave and are dominated by soil creep and landslides,have an upper convexity, straight slope lower concavity

semi arid slopes

Slopes that often consist of a small upper convexity and long basal concavity sometimes with an intervening cliff and debris slope. Rainsplash and slopewash are dominant on sparesely vegetated slopes and rockfall mechanisms on cliff faces.

skin-flows

rapid movement of thawed moisture saturated soil and vegetation over frozen ground, often in ribbon like flows. periglacial areas

equilibrium line

The boundary between the accumulation and ablation zones

calving

The breakup of glacial ice into smaller fragments

hydrostatic pressure

The pressure exerted by a fluid at equilibrium at a given point within the fluid, due to the force of gravity

roche mountonnes

These structures are bedrock knobs or hills that have a gently inclined, glacially abraded, and streamlined stoss side (i.e., one that faces the direction from which the overriding glacier impinged) and a steep, glacially plucked lee side. They are generally found where jointing or fracturing in the bedrock allows the glacier to pluck the lee side of the obstacle. In plan view, their long axes are often, but not always, aligned with the general direction of ice movement.

Younger Dryas event

a climatic event from c. 12,900 to c. 11,700 calendar years ago (BP). It is named after an indicator genus, the alpine-tundra wildflower Dryas octopetala, as its leaves are occasionally abundant in the Late Glacial, often minerogenic-rich, like the lake sediments of Scandinavian lakes. itsaw a sharp decline in temperature over most of the Northern Hemisphere, at the end of the Pleistocene epoch, immediately before the current, warmer Holocene. The eventwas the most recent and longest of several interruptions to the gradual warming of the Earth's climate since the severe Last Glacial Maximum, c. 27,000 to 24,000 calendar years BP. The change was relatively sudden, taking place in decades, and it resulted in a decline of 2 to 6 degrees Celsius and advances of glaciers and drier conditions, over much of the temperate northern hemisphere. It is thought to have been caused by a decline in the strength of the Atlantic meridional overturning circulation, which transports warm water from the Equator towards the North Pole, in turn thought to have been caused by an influx of fresh cold water from North America to the Atlantic.

translational slides

a down-slope movement of material that occurs along a distinctive surface of weakness such as a fault, joint or bedding plane. If the slip surface is straight

Earthflow

a downslope viscous flow of fine-grained materials that have been saturated with water and moves under the pull of gravity. It is an intermediate type of mass wasting that is between downhill creep and mudflow.

kame terrace

a flat-topped mound or hill composed of sorted sand and gravel deposited by meltwater in a former glacial lake.

slumps

a form of mass wasting that occurs when a coherent mass of loosely consolidated materials or rock layers moves a short distance down a slope. Movement is characterized by sliding along a concave-upward or planar surface.

thermokarst

a form of periglacial topography resembling karst, with hollows produced by the selective melting of permafrost.

kame

a hill or hummock composed of stratified sand and gravel laid down by glacial meltwater

cordilleran ice sheet

a major ice sheet that periodically covered large parts of North America during glacial periods over the last ~2.6 million years

arete

a narrow ridge of rock which separates two valleys. It is typically formed when two glaciers erode parallel U-shaped valleys.

katabatic winds

adiabatic heating of descending air (down east slopes of mountains

Ordovician glaciation

affected a large area of the old super continent (Gondwana) when it sat much farther south; and the Permo-Carboniferous (360-250 Ma) once Gondwana had started moving northward. So the greatest records of ancient glaciations are in southern Africa.

Glacial mass balance

an accounting of gains and losses of snow and ice for the glacier as a whole, or at a specific point on the glacier. There is a zone of net accumulation above the E.L. and zone of net ablation below the E.L.

varve

an annual layer of sediment or sedimentary rock.

sandurs

an outwash plain formed by meltwater from glaciers.

crescentic gouges

an upstream concave that is made by the removal of a piece of rock.

frost creep

an upwards swelling of soil during freezing conditions caused by an increasing presence of ice as it grows towards the surface, upwards from the depth in the soil where freezing temperatures have penetrated into the soil

badlands

are a unique manifestation of rapid weathering, lack of vegetation cover, rilling and gulleying, and rapid loss of sediment and slope retreat. Can occur in arid and semi-arid environments as well as along coastal or riverine cliff exposures

ice thrust ridges

are another type of moraine found in the Canadian Arctic, in which frozen sediment is pushed and thrust upwards in faulted blocks by the advancing ice sheet. These ice thrust ridges are quite common in the interior plains and the western Arctic.

Fjords

are cut by glaciers going out to sea, cutting deep channels, up to the point where the ice starts to float-common in eastern Canada.

nye channels

are cut into the underlying bedrock below the glacier.

yardang

are deep, long furrows produced by high abrasion rates(sand-blasting) of a sandy or soft rock surface

Pingoes

are ice-cored hills especially in river channels or floodplains (can be part of open or closed hydrologic systems-see Fig 9.8). The water is forced to the core area under pressure. The ice -core is usually composed of ice wedges, or lenses of segregated ice and sediments, often highly deformed. If the ice-core melts, the Pingo will have a collapsed central structure.

Palsas

are low mounds of peat usually forming as islands rising out of bogs, and like a Pingo, contain a frozen core. They form from accumulating peat layers and frost heave associated with wicking of water through peat.

flutings

are narrow, elongated, straight, parallel ridges generally consisting of till, but sometimes composed of sand or silt/clay. Flutes typically reach a height of only a few meters or less, but some may reach heights of 10 meters (~30 ft.), and may extend up to several kilometers in length. Flutes are oriented parallel to the direction of ice movement, and are formed when boulders become lodged on the subglacial floor by basal melting, and can no longer be moved by the passing glacial ice. The glacial ice must then flow around these boulders, creating elongated cavities in the ice parallel to the ice flow. These cavities in the ice are then filled with water-soaked till, which is squeezed up into the cavities as a result of high confining pressures on the glacier bed from the overlying glacial ice. As a glacier recedes, it exposes these long, low ridges of till. These glacial processes give the topography a "fluted" appearance, giving rise to the name flutes. Flutes can often be traced back to single large boulders embedded in the glacial till.

recessional moraine

are often observed as a series of transverse ridges running across a valley behind a terminal moraine. They form perpendicular to the lateral moraines that they reside between and are composed of unconsolidated debris deposited by the glacier. They are created during temporary halts in a glacier's retreat.

Glacial spillway

are produced from high-discharge outflows, or overflows, and are usually steep walled and flat floored valleys (ie our western Canadian coulees). When cut in rock (ie. Columbia flood basalts of central Washington, then these channels contain impressive potholes, grooves, boulder fields, giant current ripples, etc

ogives

are surface bands which curve down glacier (because ice moves faster near the centre) and are thought to have formed from ice coming out of icefalls. They are spaced about 50-200 m apart, which is roughly the amount the surface ice moves forward in 1 year. They are often composed of alternating white bubbly winter ice, and darker blue summer ice. Others are thought to be related to avalanching onto the upslope areas of the glacier surface

bahada

broad slope of debris spread along the lower slopes of mountains by descending streams, usually found in arid or semiarid climates; the term was adopted because of its use in the U.S. Southwest. It is often formed by the coalescing of several alluvial fans

Avalanches

can be composed of rock, snow, ice, or all of these. South-facing snow masses often avalanche to lower elevations than north-facing avalanches (in Rockies) and is probably due to more rapid melting on south-facing slopes.

ice wedges

can develop in one of three ways: 1. In pre-existing sediments (called epigenetic ice-wedges) 2. Grow syngenetically in aggrading deposits 3. Grow downwards as hillsopes are eroded. They are thought to develop in cracks that form when ground ice (near surface) freezes to below minus 15-20 oC. Moisture flows into these cracks during the thawing and refreezing seasons, preventing the cracks from closing. If there is not much moisture then the cracks may be filled with sand or silt instead. In eother situation, they often form polygonal patterns.

Flows

can exhibit large lateral spreads, and even the underlying bedrock, if it is somewhat plastic (Cretaceous shales), can be stretched (ie. seen in rotational slumps in meltwater channels of Canadian prairies. -Materials which flow behave similar to a viscous liquid, and velocity declines with depth, and usually terminate at rivers or at the foot of a slope.

heat distribution of permafrost

coldest near the surface and warms with depth

longitudinal crevasses

compressing flow produces crevasses which curve upsteam

tranverse crevasses

crevasse that commonly opens across a glacier where the slope of its floor abruptly steepens

periglacial

current frost weathering conditions, as well as those which existed in the past around Pleistocene ice margins

rothlisberger channels

cut into the ice, and generally flowing parallel to the ice slope, but may move upslope for short distances under hydrostatic pressures.

chevron crevasses

develop due to drag between ice and the valley walls. They open up at right angles to the maximum tensional stress, running about 45 degrees downstream to the valley sides.

foliation

develops from folding and progressive attenuation of pre-existing layers (former crevasses) and are produced at depth, and later become exposed farther down ice, due to ablation.

rock glaciers

distinctive geomorphological landforms, consisting either of angular rock debris frozen in interstitial ice, former "true" glaciers overlain by a layer of talus, or something in between. They may extend outward and downslope from talus cones, glaciers or terminal moraines of glaciers.

Longitudinal dunes

elongate parallel to the prevailing wind, possibly caused by a larger dune having its smaller sides blown away

permaforst ground temperatures

remain below 0oC for 2 years or more

felsenmeer

exposed rock surfaces that have been quickly broken up by frost action so that much rock is buried under a cover of angular shattered boulders. These mantles principally occur in Arctic regions and high mountain areas. Their continuity and depth varies with climate, vegetation, and rock type, but they may be as much as 4 metres (12 feet) deep. They are especially well developed on basalts and are consequently numerous on the Icelandic plateaus; they also develop quickly on sedimentary rocks and are widespread in the Canadian Arctic, extending to sea level.

saussure, hutton and playfair

first to suggest that earth was affected by ice based evidence from deposits

playa

flat-bottom depression found in interior desert basins and adjacent to coasts within arid and semiarid regions, periodically covered by water that slowly filtrates into the ground water system or evaporates into the atmosphere, causing the deposition of salt, sand, and mud along the bottom and around the edges of the depression.

glacial stairway

form as a result of glacial erosion. The term refers to the longitudinal profile of a glaciated valley that has several consecutive hanging valleys.

star dunes

have multiple arms and are formed by winds that blow from several directions throughout the year.

Thermokarst

hummocky terrain caused by melting of ice-rich permafrost, causing subsidence of the ground,and interconnections may develop between lakes, and stream erosion may occur.

snowball earth

hypothesis proposes that Earth's surface became entirely or nearly entirely frozen at least once, sometime earlier than 650 Mya (million years ago).

ice velocity thickness

increase from the head of glacier down to the E.L., and then decrease down to the terminus. Ice velocity is generally greatest near the surface and least near the base, but where the ice behaves as a rigid mass, velocity is similar throughout. Transverse velocities are highest near the central axis of the glacier, and are slowest at the valley edges (due to friction between thinner ice there, and rock wall/debris).

Milancovitch Cycles

irst suggested by Scottish Geologist James Croll in 1875. These were refined by the Serbian Mathematician Milutin Milankovitch who calculated the earth's orbital variations through time. The amount of solar radiation reaching the upper atmosphere varies according to: (a) Precession (wobbling of earth's axis) over peiods of 19 and23 ka; (b) obliquity (tilt of earth's axis of rotation within the plane of the orbit, occurring over a period of 41 ka; and eccentricity (changes in the shape of earth's orbit) occurring over periods of 95-136 ka and 413 ka. These cycles affect the seasonal and geographic distribution of solar radiation.

Facies

is a body of rock with specified characteristics,which can be any observable attribute of rocks such as their overall appearance, composition, or condition of formation, and the changes that may occur in those attributes over a geographic area. It is the sum total characteristics of a rock including its chemical, physical, and biological features that distinguishes it from adjacent rock.

meltout till

is a deposit made from stagnant or very slow moving debris rich till. The debris is slowly released from ice that is melting from above and below, esp. common near ice-margins, and usually deposited on top of lodgment till. It also generally has a fabric with long-axes of pebbles parallel to ice movement, but generally not as strongly preserved as in lodgement till, and may have some transverse fabric where compressive stress conditions were very strong.

kame delta

is a glacial landform formed by a stream of melt water flowing through or around a glacier and depositing material, known as kame (stratified sequence of sediments) deposits

glacial plucking

is a glacial phenomenon that is responsible for the erosion and transportation of individual pieces of bedrock, especially large "joint blocks". This occurs in a type of glacier called a "valley glacier". As a glacier moves down a valley, friction causes the basal ice of the glacier to melt and infiltrate joints (cracks) in the bedrock. The freezing and thawing action of the ice enlarges, widens, or causes further cracks in the bedrock as it changes volume across the ice/water phase transition (a form of hydraulic wedging), gradually loosening the rock between the joints. This produces large pieces of rock called joint blocks. Eventually these joint blocks come loose and become trapped in the glacier.

truncated spurs

is a ridge that descends towards a valley floor or coastline from a higher elevation, that ends in an inverted-V face and was produced by the erosional truncation of the spur by the action of either streams, waves, or glaciers. They can be found within mountains, along the walls of river valleys, or along coastlines.

barchan dune

is a type of transverse ridge with a crescentic shape because winds are stronger around the outside edges, so horns (wings) are oriented downwind. May start out with a meagre sand supply, but as sand accumlulates may transform into a barchanoid ridge, and with even more accumulation of sand, into a longitudinal dune.

cirque

is an amphitheatre-like valley formed by glacial erosion.

ablation zone

is composed entirely of ice. During the winter, the ice of this zone is covered with snow, which entirely melts away in summer.

deformation till

is formed when subglacial material is transported under deforming (and obviously warm-based) conditions at the base of the ice. It is often composed of weak rock or unconsolidated sediment that has been detached from its source by the glacier and this has often distorted the original sedimentary structure, and foreign material from higher up in the ice has been incorporated. These at the snout of the ice can have strong flow and squeeze characteristics, with material flowing or squeezing into crevasses, or subglacial channels

lodgement till

is plastered onto the bed when frictional drag is greater than the shear stress imposed by the advancing (or retreating) warm based glacier.

stemflow

is the flow of intercepted water down the trunk or stem of a plant

interflow

is the lateral movement of water in the unsaturated zone, or vadose zone, that first returns to the surface or enters a stream prior to becoming groundwater.

plastic limit

is the minimum moisture content that still allows a soil to be moulded (increases with clay content

liquid limit

is the moisture content at which a soil begins to flow

till

is the name given to unsorted, unstratified sediment laid down directly by glacial ice.

interlobate moraine

mark the final stages of glaciation where ice is separated into lobes occupying topographical depressions and debris is deposited between these lobes

extensional flow

may also occur where the bed steepens, then thins and becomes crevassed, and where velocity increases because of sliding. Crevasses curve downwards to the ice bed in a downglacier direction. Here the ice entrains debris and carries it along near the base of the ice

splaying crevasses

meet the valley side at an angle of less than 45 degrees.

stratification

results from annual layering of clean white winter ice, alternated with bluish sediment laden (and refrozen) ice of summer periods.

entrainment

meltwater is driven from areas of thicker ice in the interior of glaciers where it is usually has an unfrozen and porous substrate, to areas near the margins of glacier where colder ice is passing over frozen and impermeable terrain. -high pore-water pressures may freeze rock debris or till up (higher) into moving ice. -debris is usually carried in discontinuous and closely spaced layers near the base of ice, and is overlain by a layer of ice which contains more dispersed and finer debris. These layers range in thickness and homogeneity depending on the amount of lateral and vertical mixing within the ice. -much debris can also be incorporated at the surface of the glacier by entrainment along the valley margin and by rock falls (avalanches, dust, volcanoes, etc.). In the accumulation (extending) ice zone the material works its way down into the ice, whereas any debris entrained or added to the ablation (compressional) zone of the glacier stays near the surface and is added to the debris which is being sheared up in this zone.

location of periglacial climate

northern Eurasia and North America, and are composed of both Tundra and Boreal Forest, where permafrost can be discontinuous. -it does occur on high mountains, even on the equator, where it usually occurs above the treeline.

striae

ny of the parallel scratches or grooves on the surface of a rock caused by abrasion resulting from the passage of a glacier, motion on a fault surface, etc.

drumlin

occur singly of in schools and look like inverted spoons and usually formed parallel to ice movement and may be related to progressive slowing and thinning of ice as it travels to the terminus as some have built in layers around pre-existing material

compressional flow

occurs where the bed becomes concave or flattens, ice thickens, or velocity decreases. and where valleys narrow, at the foot of icefalls, or at the glacier terminus crevasses curve up to the ice surface in a downglacial direction, facilitating the evacuation of debris from the base of the ice, and facilitating erosion of the bedrock. Delivering debris to the surface of the ice, and to the snout.

ice flow

occurs within ice crystals (hydrogen atoms sliding on their basal planes) and between ice crystals, as crystals move relative to each other and as crystal growth and re-crystallization and migration of crystal boundaries takes place. Again, small increases in ice thickness cause much greater increases in the rate of creep.

flow rate of a glacier

of a glacier increases with ice temperature and water content

rythmites

of layers of sediment or sedimentary rock which are laid down with an obvious periodicity and regularity. They may be created by annual processes such as seasonally varying deposits reflecting variations in the runoff cycle, by shorter term processes such as tides, or by longer term processes such as periodic floods.

Rogen moraine

often associated with with drumlin,are formed by stagnant ice and deformation of sediment beneath ice. May have been formed by retreating ice in a shallow lake.Shaw sees these as ripple forms

dead ice moraine

often contain linear and curvilinear forms deposited in open crevasses exhibit thrust planes and lines of weakness within the ice

falls/topples

often triggered by frost, water, root wedging, earthquakes, rapid erosion causing voerhangs in mountainous terrains. Melting of ice-rich sediments in the north (Arctic) transfers large amounts of sediments to the oceans-mostly through these

pater-nostre lake

one of a series of glacial lakes connected by a single stream or a braided stream system. The name comes from the word Paternoster, another name for the Lord's Prayer derived from the Latin words for the prayer's opening words, "Our Father"; They are so called because of their resemblance to rosary beads, with alternating prayer beads connected by a string or fine chain.

Erratics

piece of rock that differs from the size and type of rock native to the area in which it rests.

shrinking limit

point at which volume is no longer reduced with continued drying

periglacial flow

presence of frozen ground beneath surface can lubricate overlying thawed sediment and cause it to flow. Alternating freezing and thawing can facilitate such flows

Venetz

proposed that Switzerland had been glaciated,

physical movement of glaciers

ranges from 10-300 meters/yr for temperate mid-latitude areas, and for ice streams and outlet glaciers can occasionally range up to several kms/yr. Generally cold-based glaciers move very slowly.

gibber

rock- and pebble-littered area of arid or semi-arid country in Australia. The rocks are generally angular fragments formed from broken up duricrust, usually silcrete, a hardened crust of soil cemented by silica (SiO2). The gravel cover may be only one rock fragment deep, or it may consist of several layers buried in fine-grained material that is thought to have been blown in. It is generally considered a result of mechanical weathering because silica is almost inert to chemical weathering

distal sediments

sediments tend to be finer while bedload is deposited near the shore (delta).

Creep

slow downslope movement of particles that occurs on every slope covered with loose, weathered material. Even soil covered with close-knit sod creeps downslope, as indicated by slow but persistent tilting of trees, poles, gravestones, and other objects set into the ground on hillsides.

de charpantier

studied modern glaciers in Switzerland, and concluded that the country had been extensively covered by such glaciers in the past.

surging

sudden advance of ice (from 150 m to 6 km/yr) causes rapid advance of the terminus, may produce looped medial moraines, intense folding , and dense surface crevassing

Bolton

suggested that as ice thickens, the abrasives at the base of the ice move more and more slowly, until they can not move any longer, and they are then deposited as lodgement till.

soilfluction

the gradual movement of wet soil or other material down a slope, especially where frozen subsoil acts as a barrier to the percolation of water.

col

the lowest point on a mountain ridge between two peaks

cryoturbation

the mixing of materials from various horizons of the soil down to the bedrock due to freezing and thawing

saltation

the movement of hard particles such as sand over an uneven surface in a turbulent flow of air or water.

Dansgaard-oechesher events

the periodic cold spells preceding the rapid warming events

talus

the pile of rocks that accumulates at the base of a cliff, chute, or slope.

cryostatic pressure

the pressure exerted on the rock/soil by existing ice body such as glaciers, ice sheets,

isostatic rebound

the rise of land masses that were depressed by the huge weight of ice sheets during the last glacial period, through a process known as isostatic depression.

Mass balance gradient

the slope of line produced by plotting mass balances along length of a glacier against elevation

active layer

the zone which thaws during the summer and very much impacts the local hydrology, soil formation, vegetation cover, and biogeochemical processes.

badland

type of dry terrain where softer sedimentary rocks and clay-rich soils have been extensively eroded by wind and water.[1] They are characterized by steep slopes, minimal vegetation, lack of a substantial regolith, and high drainage density.

Talik

unfrozen areas within permafrost and can be oriented vertically or horizontally

paraboic dunes

usually found on coasts, have arms (wings, horns) pointing upwind, because vegetation has anchored the edges of the dunes

subsistence

vertical downward movement or sinking of surface depoists or rock. May involve quite large areas. Usually due to mining, coastal erosion, piping, subsurface solution, melting of ground ice, volcanic activity, loading, deglaciation, etc

gelifluction

very similar to solifluction, is the seasonal freeze-thaw action upon waterlogging topsoils which induces downslope movement. It is prominent in periglacial regions where snow falls during six to eight months of the year.

dustbowl era

was a period of severe dust storms that greatly damaged the ecology and agriculture of the American and Canadian prairies during the 1930s; severe drought and a failure to apply dryland farming methods to prevent wind erosion (the Aeolian processes) caused the phenomenon.

dry snow zone

where there is little or no melting (only in severe cold climates of Antarctica and Greenland, and in highest mountains of Alaska and Yukon) .