EAS 225 Permafrost and Fluvial

What is permafrost?

Ground that remains at or below 0 degrees for at least two consecutive years.

Define pariglacial

conditions, processes and landforms associated with cold, non glacial environments

Define arctic amplification

processes by which small temperature changes cause large impacts in northern areas

What is the active layer?

The layer above permafrost that thaws in summer and refreezes in winter

What are the three soil water states?

gravitational, capillary, hygroscopic

Differentiate between the three soil water states.

G drains freely under gravity, C is held in soil pores by surface tension, H is tightly bound to soil particles

What is freezing point depression in soils?

lowering of freezing temperature below 0 degrees

What kind of soils have more unfrozen water at subzero temperatures?

Fine grained soils

How much does water expand after freezing?

about 9%

Why is vegetation important in permafrost?

it plays a critical role in insulating the ground form the atmosphere

Where is the presence of vegetation most influential?

at the forest tundra transition where the thickness of snow is largely controlled by the presence or absence of vegetation.

What are the 3 soil properties that influence ground temperatures?

thermal conductivity (high moisture, high mineral, high thermal conductivity), heat capacity (varies with composition and water content), albedo and surface cover

What are the three zones water can exist in?

suprapermafrost, intra-permafrost, sub-permafrost

What is a talik?

unfozen ground with permafrost zone

What is a peat plateue?

areas of raised peatland that are ice-cored (typically 0.5-1.5m above water table)

What is a fen?

area of water transport through peat/peatland in permafrot areas (generally thawed throughout)

What are icecored landforms?

landforms created by growth and maintenance of ground ice, usually raised above the surroundings by ice growth.

Define Ground ice

a generic term for all types of ice that exists in premafrost

What are cyrostructures?

patterns formed by ice inclusions in frozen ground

What is ice segregation?

insitu growth of ice lenses as a result of water movement to a freezing front within permafrost

What conditions must be met for ice segregation to occur?

water needs to be supercooled with some dissolved ions/brines

What is ice injection?

ice that forms due to pressuried water either at the base of permafrost, within, or withi the active layer

Define excess ice

ice that exceeds the pore space of the host sediments

What is the relationship between excess ice and thaw sensitivity?

As you have more excess ice your thaw sensitivity will rise

Define frost shattering

mechanical breakdown of rock caused by the pressure of water freezing and expanding i crocks and pores

What are scree slopes?

frost wedging/shattering and low ice flux

Define frost heaving

growth of ice insitu in the near surface

What is frost creep?

Where the movement of soil down slope heave and settle down the slope

Define soilifluction and give the more general name

gelifluction. The creation of lobes from repeated frost creep over time (10s to What fors ice wedge100s years)

What forms ice wedges and what do they look like form a birds eye view?

Forms due to thermal contraction cracking. It looks like a pattern of polygons from above

What is another name for closed system pingos?

mackenzie valley type

Where are closed system pings found?

in continuous permafrost zone

how do closed system pingos form?

form in drained lake basins through growth of segregated intrusive ice

Where are open system pingos found?

discontinuous permafrost zones

How are open system pingos formed?

formed through the growth of intrusive ice either from subpermafrost groundwater or intra-permafrost ground water

Define seasonal frost mounds

like a small pingo except forms in active layer

What are bogs?

ambotrophic (fed by rainwater) areas with organic rich acidic (4-7) soil that may be frozen or unfrozen

What are fens?

areas of movign water potentially interacting withmineral soil through peatland. They are ground water and surface water fed. Basic (6-8)

What are palsa and peat plateaus?

ice cored peatland landforms formed through the lifting of peat above surface water through growth of segregated ice.

What does thermokarst mean?

terrain effects of permafrost landscapes due t loss of ground ice

What are the two kinds of permafrost landslides?

Thaw slumps (retrogressive thaw flow slides) and active layer detachment slides

What is a thaw slump?

A deeper landslide associated with loss of abundant ground ice from headwall driven by gravity/slope processes

What are the characteristics of active layer detachment slides?

A shallow landslide associated with the seperation of active layer from the top of permafrost. Usually following dsturbace (fire, rainfall event). Typically occurs in fall when active layer is at its maximum

What are the three main strategies for constructing on permafrost?

insulating through coarse gravel embankments, insulating my raising infrastructure, and artificially cooling the ground

What are the pipes on stilts above the ground?

ultiidore

What are those things on the pipeline?

thermosyphons that use convection heat control

Define fluvial

processes related to streams and rivers (adj)

define alluvial

synonymous with fluvial

define alluvium

refers to products transported by rivers/streams (noun)

What is fluvial geomorphology?

The study of the effects of running water of the land surface

WHat is needed for fluvial geomorphology?

sediment transport

What is the order scheme for rivers and streams called?

Strahler stream order

What are 6 factors that effect run-off vs infiltration?

vegetation, permeability, temperature, saturation, slope/aspect, amount and intensity of precipitation

What equation would you use to measure discharge?

Q=w*d*v use (riemman sum)

What does this equation represent?

the Q at a particular stage (water surface elevation)

How would you calculate the recurrence interval?

RI=(number-1)/rank

How would you find the probability form this?

1/RI

What does RI assume?

Assumes that the drainage basin is the same, constant data quality and does not ccount for climate change

Defibe weathering

breaking down of rocks/sediments by chemical or physical processes

Define erosion

transportaion of material/ removal of weathering products

What are the two factors effecting stream velocity (drivining forces)

gradient and discharge

What are the 3 resisting forces?

channel shape, channel roughness, internal viscosity of water and turbulence

What are the two channel shapes?

proximal (wide & shallow) with high width:depth ratio and Distal (smaller wetted perimeter) and lower width:depth ratio

How does channel roughness change as grain size changes?

decreases as grain size decreases

What equation can you use to express velocity taking roughness into account?

v=(R²/³*S¹/²)/n where R is the wetted perimeter, S is th eslope of the water, and n is the manning number

What does Reynold´s number represent?

A measure of turbulence

What equation can you use to measure turbulence?

R_e=(v*u*p_fl)/mu where v=velocity, u=wetted perimeter, p_fl=fluid density, and mu=viscosity of fluid

Based off of Reynold´s number, what is considered turbulent?

R_e>500

How does turbulence influence instantaneouss velocities?

higher turbulence leads to higher instantaneous velocties

What are the axises on Hjulstrom curve and what does it demonstrate?

x=particle size and y=mean velocity. Represents sediment entrainment

What does the swoosh on the Hjulstrom curve represent?

critical sheer stress (shear stress needed for sediment entrainment)

What is the relationship for sand and larger grain sizes?

postive

what is the relationship for very fin grain sizes?

negative

how do fain grain sizes behave if velocity drops below critical sheer stress after it has been reached?

they stay in motion

What are the axises for Sheild´s curve

x=grain diamter/laminar sublayer and y=sheild´s number

What is taken into account in Sheild´s curve?

sheild´s number, critical sheer stress, gravity, sediment particle density, fluid density, diameter of grain, laminar sublayer

What are the three compenents for sediment transport?

bedload, suspened load, and dissolved/chemical load

What are the 6 photointerpetive elements?

Tone/colour, shape, relative size, texture, pattern, association/sight

Who originated the ice age theroy?

Louis Agassiz

What was a specultaive casue for ice ages?

Astronomical theory aka Milankovitch theory

What are the 3 importat variables in the Milonkavitch theory?

Eccentricity (shape of orbit), Obliquity (titlt), and precession (wobble)

What combination of these variables promotes ice formation?

elliptical, low obliquity, and axis when away from the sun in summer

Who is Cesare Emiliani?

Designed experiments to test temperature dependence on isotope composition of forams.

What is glacial startigraphy?

stacked sequences of alternating glacial and non-glacial sediments providing evidence for mutiple glaciations

What are some factors that effect the distribution of glaciers?

ablation, temp+precipitation

What is mass balance?

net difference between accumulation and ablation overtime (typically winter summer cycle)

What are two traits of cold based ice?

frozen to its bed and no subglacial water, and only motion is due to internal deformation

What are 3 traits of warm based ice?

basal ice is at its pressure melting point, there is liquid present in the subglacial environment, promotes sliding of ice over the bed

What is a polythermal glacier?

goes back and forth between cold and warm-based (spatially or temporally)

What size are ice sheets vs ice caps?

Ice sheets>50,000km² >ice caps

What is an ice field?

glaciers fills an elevated basin, commonly with radiating outlet valley glaciers

What is a cirque glacier?

occupies a small basin on a mountain slope

What are piedmant glaciers?

lobe-shaped glaciers formed when steeper ice spills out into a broud lowland

What is a calving margin?

floating tongue of glacier ice with chunks of ice falling off

What are ice shelves?

the portion of an ice sheet or ice cap that flows out onto the ocean as a floating/moving ice mass

What are tidewater glaciers?

glaciers that terminate at sea level into the ocean

What are the three kinds of glacier motion?

internal deformation, basal sliding, subglacial deformation

What is Glen´s flow law?

strain rate e=Aτⁿ

What does Glen´s flow law relate?

ice deformation to sheer stress and ice properties which is controlled by ice thickness and surface slope

What is a surging glacier?

a transient episode of rapid movement 10-100x the normal”velocity of the glacier (internally drive not related to climate changes)