geog exam 4

chemical weathering

decomposition of minerals in the rock (Ie. the chemical composition change), it requires water, and occurs faster in hot humid climates

examples of chemical weathering

hydrolysis & hydration and dissolution of carbonates

denudation

refers to the lowering of continents to sea level

physical weathering

reduces the size of rock masses without altering the chemical composition (disintegration). converts masses of rock into numerous smaller pieces that can be more readily removed by erosion

the main physical weathering processes include

frost action, salt weathering, pressure-release jointing, vegetation/organism

definition of geomorphology

balance of uplift and reduction

shear strength

holds the material in place

shear stress

pulls material downslope

factor of safety =

shear strength/ shear stress

discontinuous creep

Ratchet-like movement due to soil expansion and contraction.

needle ice creep

Driven by wetting and drying, freezing and thew. they are typically few mm/yr

slow mass movements

solifluction and gelifluction

solifluction

combination of frost creep and gelifluction. rate 1-5cm/year

gelifluction

the slow movement downslope of saturated soil over frozen ground during the spring and summer

quick clay flow

House-shoe-shaped forms. Slumping around their headwalls and mudflow in their floors. develop within Leda clay marine salts are leached out reducing soil strength

slushflow

Incorporates loose debris. Most often in mountain environments and often occur down existing river channels. non-sorted debris that piles up randomly.

mudflows

most fluid, fastest flow(80km), ,most dangerous. at least 50% fine material and >30% water. long narrow track, expanded depositional area

debris flow

Similar form to mudflows but contains large particles and usually moves a little more slowly. most often caused by heavy precipitation

slides

movements long one or more discrete failure surface

slump

failure surface is deep and curved

rock slide

Failure along a flat plane parallel to the ground. occur where bedding planes and slopes dip in the same direction. and occurs 5 times a century in the Canadian cordillera (turtle mountain )

debris slides

failure of non-consolidation materials along a plane parallel to the ground

glaciers definition

A glacier is a mass of ice originating on land by recrystallization of snow or other forms of solid precipitation and showing evidence of past and present movement

how much fresh water is on earth

2.78%

eustatic sea level change

change in volume of water

isostatic sea level change

change in land position

formation of glaciers leads to

eustatic sea level fall

continued growth of glaciers leads to

isostatic sea level rise due to ground depression from weight of ice

glaciers begin to melt leads to

eustatic sea level rise

further decline of glaciers leads to

isostatic sea level fall as land rebounds from the weight if glaciers being removed

formation of glacial ice

fresh snow compacts and undergoes freeze-thaw to become more dense firn (600-700kg/m) and it continues to freeze-thaw and compact to glacial ice

continental ice sheets

Large areas, conflicted flow due to gravity, ex. Greenland, Antarctica, Laurentide ice sheet

ice caps

not constrained smaller than ice sheets, dome-like surfaces, polar and subpolar regions

ice shelves

Glaciers that float out onto the ocean, sensitive climate change indicators, ex. Antarctica, Ellesmere island

ice fields

Not dome-like, topograhic restraint, many outlet glaciers, ex. Columbia ice fields, St Elias icefield Yukon

valley glaciers

contained in a valley, may be fed by an ice field steep, flow due to gravity

accumulation zone

positive net balance, more snow accumulation than melt

ablation zone

negative net balance, more melt than snow accumulation

equilibrium line altitude

Highest elevation that the snowline reaches at the end of the summer, separates accumulation and ablation.

deep in the glacier ice behaves in what manner

plastic

near the top ice behaves in what manner

brittle

Glacier flow can be lubricated by

water below the glaciers

these combine with stress from movement to create

crevasse (cracks at the surfaces)

periglacial

Areas where cold climates and processes dominate often close to ice sheets in polar environments that do not have ice cover but can be influenced by permafrost and often have ground ice

permafrost

Earth materials (rock, soil, or organic) that remains at or below 0C for 2 or more consecutive years

active layer

This is the soil and rock layer of varying thickness that thaws each summer above permafrost

continuous permafrost

90-100% coverage

extensive discontinuous

50-90% coverage

sporadic discontinuous

10-50% covearge

isolated

<10% coverage

alpine

present at high elevation, absent at adjacent low elevations

subsea

relict from times when sea levels were lower

taliks

unfrozen ground within the permafrost, usually under water bodies (e.g. Mackenzie delta)

palsa

Low frost mounds with a core of inter-layered ice and peat. less snow accumulation results in frost heave. snow drifts away from the topographic high point in future years

patterned ground

Frost action processes result in the rearranging of particles due to expansion of water during freezing.

ice wedges

Freezing opens cracks in the ground that then can fill with water.

As the water freezes it heaves and pushes soil resulting in further cracking.

Process keeps repeating itself over a long time

closed pingo

occurs in areas of continuous permafrost

usually form in flat areas as a result of lake drainage.

rock glacier

Transition between glacier and periglacial. Accumulation of rock debris with an ice core. it has a glacier shape

thermokarst

Melting of ground ice allows the development of irregular features. can be problematic for infrastructure

denudation examples

weathering, mass movements, erosion

exfoliation/ pressure-release jointing

expansion of rock from removal/erosion of overlying rock

if FoS is great then 1 (>1)

Slope is stable because shear strength is greater than shear stress

if FoS is less then 1 (<1)

Slope is unstable because shear stress is greater than our shear strength

glaciers contribute to

change in sea level