Glaciated Landscapes Flashcards

Question

What are basal sliding and internal deformation affected by and what are the different zones of the glacier?

Answer 1

Move due to gravity but influenced by: Gradient - steeper gradient = more movement Ice thickness - affects basal temperature and pressure melting point Balance - positive balance causes advance Upper zone - ice is rigid and brittle so breaks to form crevasses Lower zone - ice deforms due to pressure Top and middle move more rapidly than the sides and base due to frozen areas and friction

Answer 2

Warm based glaciers Slippage - circular motion that can cause ice to move away from back wall/hallows Creep - slow downwards movement of loose rock and soil down a gentle slope Bed deformation - movement of soft sediment beneath ice. More effective in temperate areas as underlying material is water saturated

Answer 3

Cold based glaciers Intergranular flow - individual ice crystals move relative to each other Laminar flow - individual ice crystals move along layers within the glacier

Answer 4

A variety of interconnected climate and geomorphic processes

Answer 5

Freeze thaw - water enters cracks, freezes and expands 10% - pressure causes split Frost shattering - low temperatures water in pores freezes and expands - disintegration Pressure release - weight of overlying ice falls due to melting - rock expands and fractures

Answer 6

Oxidation - some minerals will react with oxygen from air or water Carbonation - rainwater dissolves CO2 from atmosphere to produce carbonic acid which reacts with calcium carbonate Solution - mineral dissolves in water Hydrolysis - chemical reaction between rock minerals and water Hydration - water molecules added to rock minerals to create new larger minerals

Answer 7

Tree roots - grow into cracks/joints and exert outwards pressure Organic acids - produced during plant decomposition and animal litter cause soil water to become more acidic and react with minerals - chelation

Answer 8

The movement of above ground material (regolith) down a slope Rockfall - slopes of 40 degrees or more - material falls to base of of the slope by gravity Slides - may be linear with movement along a fault or bedding plane, or rotational with movement along a curved or slip plane

Answer 9

Dependent on: slope angle, particle size, temperature, saturation

Answer 10

Abrasion - material embedded in the glacier rubs away at the valley sides and floor. Striations left behind. Fine debris is called rock flour Plucking - glacier freezes on and into rock. As ice moves it pulls away the rock. Mainly happens at the base where jointed rocks have been weakened by freeze-thaw action - jagged left Nivation operates under patches of snow - freeze-thaw and chemical weathering loosen rock with meltwater removing debris. This repeated melting/freezing forms nivation hollows

Answer 11

presence of basal debris, debris size and shape, hardness of particles, ice thickness, basal water pressure, sliding of basal ice, movement of debris at the base, removal of fine debris

Answer 12

Carry large amounts of debris which can come from wide range of sources such as rock falls, avalanches, debris flow, aeolian deposits, eruptions, plucking and abrasion Supra-glacial - movement on the surface En-glacial - movement within the ice Sub-glacial - movement at the base of the glacier

Answer 13

Where ice melts at the snout, material is deposited Drift →till or outwash →till becomes lodgement till (pressed into floor in advance) or ablation till (left behind during retreat) Till - angular, unsorted, unstratified vs outwash - smooth, sorted, stratified

Answer 14

Armchair shaped rock basins with rock lip that occur on north/east slopes due to less insolation and greater accumulation 1. Nivation on mountains creates a small hollow, this collects snow and enlarges annually. At a critical depth the ice rotates 2. Plucking steepens the back wall and adds debris - retreats due to freeze-thaw weathering 3. Abrasion occurs at the base as it flows forward and down - deeper depression 4. Meltwater and debris from freeze-thaw weathering above the corrie glacier drop down a deep crevasse that opens up between the glacier and back wall - causes movement as lubricates base causing more abrasion 5. Glacier rotates and more erosion deepens basin, at the outlet, ice moves upwards so less erosion forms a lip erosional

Answer 15

Sharp ridge formed where two corries erode back-to-back or alongside each other erosional

Answer 16

Back walls of three or more corries erode a hill or mountain top, the back walls meet to create a sharp central mass erosional

Answer 17

Troughs are formed when glaciers flow down pre-existing river valleys. Deepen and change the v-shape to a u-shape. Straight, wide-based, steep-sided erosional

Answer 18

result of the valley of a tributary being eroded at a slower rate than main river erosional

Answer 19

Ice, meltwater and sub-glacial debris combined have huge erosive power forming: Areas protruding from the river valley sides (spurs) removed forming truncated spurs Areas of resistant rock on the valley floor are not completely removed and left as RMs, smooth up-valley side created by abrasion and jagged down-side due to plucking. erosional

Answer 20

Scratches or grooves made by debris embedded in the base of the glacier Indicate the direction of ice flow erosional

Answer 21

Formed by an ice sheet Huge erosional depressions in the landscape created by the erosive action of ice sheets such as the Laurentide Ice Sheet erosional

Answer 22

Landforms created when debris carried by glacier is deposited Lateral - from frost-shattering of valley sides, carried at the edge of the glacier, when melting happens a side embankment is formed Terminal - high mound extending across the valley to mark the maximum advance Recessional - mark an interruption in the retreat of the ice depositional

Answer 23

Individual pieces of rock picked up and carried by ice over kms to be deposited in areas with different geology. Pebble → boulder depositional

Answer 24

Smooth, elongated mounds of unsorted till (rock, clay, sand). Long axis runs parallel to ice flow and often found in swarms Only theoretical theories but could include Logement of subglacial debris, reshaping of previously deposited material by ice, material accumulating around an obstruction, deposition of material as ice thins Depositional

Answer 25

Huge, wide, flat areas where there is a covering of till (sand/gravel). Composition varies and depends on nature of rock the ice has moved over Created by ice sheets depositional

Answer 26

Glacio-fluvial landforms exist as a result of climate change - produced by meltwater during deglaciation - high velocity flow - loss of energy due to decrease in discharge causes deposition

Answer 27

When global temperatures rise, glacial periods end and interglacial periods begin 10,000-15,000 years. Rivers deposit outwash: Small pieces of material carried by meltwater streams which have less energy than ice Smooth and rounded particles Sorted - larger material further up valley Stratified vertically with distinct seasonal and annual layers Sudden melting can cause high discharge - large amounts of sediment deposited (jokulhlaup)

Answer 28

Depositional

Answer 29

Undulating, winding mounds of unevenly deposited sand and gravel that follow ice movement Delta - englacial streams emerge at snout - lose energy and deposit. Supra-glacial streams flow to the edges of glaciers and flow into lakes at ice margin. Stream loses energy as it meets static water and deposits Kame terraces - supra-glacial streams on the edge of a glacier pick up and carry lateral moraine material, gets deposited when glacier retreats (rounded and sorted)

Answer 30

Long, narrow ridges of sorted and stratified course sand and gravel Form when water in subglacial tunnels deposits what it is carrying when glacier melts and retreats Deltaic deposits left when meltwater flows into a lake trapped by moraine deposits

Answer 31

Large flat areas which contain deposits from pro-glacial streams and meltwater streams running out from the snout of the glacier - course material - found near to end of glacier and finer clay - carried across the plain and deposited Meltwater streams that cross the plan are braided (divide as the channels become clogged) - kettle holes formed when blocks of ice that have been washed onto the plain melt and leave a gap in the sediments

Answer 32

Repeated retreat and advance of ice Geomorphological processes such as weathering and erosion Colonisation of vegetation in post-glacial times e.g. mosses/grasses Rising temperatures lead to more melting and further expanses of outwash

Answer 33

a result of climate change Areas with - permafrost (permanently frozen soil and regolith) discontinuos/sporadic, seasonal temperature variations with a brief ‘summer’ above 0, freeze-thaw cycles as dominant process Found in high latitudes and altitudes

Answer 34

Below the surface and leads to vertical sorting of material in the active layer Stones in active layer heat up and cool down faster than surroundings Water beneath the stones freeze and expand pushing stones to the surface

Answer 35

During summer melting, water percolates down to subsurface geology During winter months this freezes and expands 10% pushing ground surface up

Answer 36

Frost heave pushes larger stones to surface Ground is domed so stones roll down to edges due to gravity - pattern of a network of stone polygons, on angled slopes polygons becomes stretched and enlarged into garlands

Answer 37

Dome shaped hill with core of ice two types

Answer 38

Found in areas of continuous permafrost develop beneath lake beds ice core growth is hydrostatic Deep lakes over 2m may remain unfrozen in winter Permafrost layer at lake bed insulated from cold and thaws Area of unfrozen waterlogged ground now sandwiched between lake and permafrost Lake drains - bed no longer insulated so waterlogged bed freezes Localised differences in pressure between the lake, freezing lake bed and permafrost causes newly freezing water together forming an ice lens that expands, pushing the lake-bed sediments above it in a dome shape Ice lens continues to grow as long as there is still unfrozen ground in the lake based as a source of pressurised water to add to the core

Answer 39

Areas of discontinued permafrost Found in valley bottoms Growth of ice core is hydraulic Water seeps into upper layers of ground and flows from higher surroundings areas under artesian pressure Water accumulates in flat, low-lying areas between the upper areas of permafrost or soil and frozen ground beneath the water and freezes Freezing ice core expands doming the overlying layers Grow as pressurised water continues to flow in from surroundings

Answer 40

Slow flow of saturated regolith down a gradient Summer melt of water in upper layers of permafrost leads to large amounts of water which can’t drain due to permafrost. Lubrication means soil is moved on slopes Mass movement (soil creep) makes frost heave domes less obvious

Answer 41

Rise in temperature causes colonisation by vegetation Pingos thaw and collapse, creating circular depressions called ognips

Glaciated Landscapes Flashcards

(65 cards)