exam #4 Flashcards
Define denudation. What are the elements of denudation
lowering of continental surfaces. Weathering, mass wasting, erosion
explain physical and chemical weathering
physical: reduces size of rock masses without altering chemical composition
chemical: decomposition of minerals in the rock -> chemical composition of rock changes
what are the processes of physical weathering
frost action: freeze/thaw cycles
salt weathering: crystallization breaks up rocks
pressure-release jointing: slab-like layers/sheets break loose
biological forces: plants and organisms
explain the chemical weathering processes
1) hydrolysis: granular disintegration
2) hydration:
3) dissolution of carbonates: how weathering of limestone occurs
what is karst topography
solution of carbonate rocks (limestone) can result in the landscape being pitted, bumpy surface topography with underground channels and caverns
Which climates do physical and chemical weathering dominate in?
physical: drier, cooler climates
chemical: moister, wetter climates
define mass movement
process of a body of material is moved downslope under the influence of gravity
the gravity/forces on a slope diagram ***
define Fp and Ff
define angle of repose and angle of sliding friction
angle of repose: steepest angle that can be attained by loose material without moving downslope (typically 33 to 37 degrees). i.e., angle at which sliding ceases
angle of sliding friction: angle at which dry, unconsolidated material fails. i.e., angle at which sliding commences
what does the coulomb equation represent? what is the equation? what are the variables?
shear strength = shear stress = normal stress * tan(angle of internal friction) plus cohesion
how does water affect soil cohesion
shear strength = shear stress when there is no movement. soil cohesion is low when very dry, low when saturated and high when pores are partly full and under suction
what’s the coulomb equation with water?
water affects the normal stress
shear strength = shear stress = (normal stress - porewater pressure) * tan(angle of internal friction) plus cohesion
what’s the factor of safety? is the slope stable are unstable when FoS is > or < than 1
FoS = shear strength / shear stress
FoS > 1 = slope stable
FoS < 1 = slope unstable
what are the trigger mechanisms ?
- precipitation, weathering, earthquakes, changes in loading, changes in slope, vegetation changes
is an avalanche a mass movement?
NO
all the diagrams for mass movements
rissa quick clay slide
what’s the difference between isostatic and eustatic changes
isostatic: related to land position
eustatic: related to water volume
what are the environmental significance of glaciers..
1. formation of glaciers and ice sheets (iso/eu rise/fall in sea level)
2. further growth of ice sheets (iso/eu uplift/depression of land, rise/fall in sea level)
3. ice sheets melt (iso/eu rise/fall in sea level)
4. decline of ice sheets and glaciers (iso/eu rise/fall of land, rise/fall in sea level and iso/eu rise/fall in sea level)
- eustatic, fall
- isostatic, depression, rise
- eustatic, rise
- isostatic, rise, fall, eustatic, rise
types of glaciers**
How can an ice shelve be used/what mechanism to show the sensitivity of climate change in systems?
Ground penetrating radar can be used to tell exactly how big the glacier is -> can compare size
what’s a surge?
rapid onset/increased velocity of a glacier
define permafrost, periglacial and active layer
permafrost: earth materials that remain at or below 0 degrees for 2 or more consecutive years (perennially frozen ground)
periglacial: areas where cold climates dominate that do not have an ice cover
active layer: soil and rock layer of varying thickness that thaws each summer (seasonally thawed ground)
define continuous, discontinuous, mountain, sub sea permafrost
continuous: all surfaces (>90%)(besides deep lakes) covered
discontinuous: extensive (50-90%) and sporadic (10-50%) coverage
mountain: when permafrost is present at high elevation but not in adjacent lowlands/valleys
sub sea: determined by history (due to sea being -2 degrees)
factors that affect mountain permafrost
elevation, surface, subsurface, water availability, snow cover
different types of active layers
type 1: bedrock
- low ice, thick active layer, high arctic/mountain areas, changes in surface conditions, fast response time
type 2: rock glacier
- high ice, thick active layer, rock glaciers, changes in MAGST/snow depth, slow response time due to high ice content
type 3: mineral soil
- low to high ice, medium active layer, wherever soil s well developed, changes in MAGST/snow depth/vegetation, moderate response time
type 4: organic
- moderate ice, low active layer, lowland/valleys, changes in MAGST, snow depth, forest fire, very slow response time
type 5: submerged
- high ice, shallow active layer, edge of lake, …changes in lake level, dependent on hydrology
why did the rissa quick slide happen? where did it occur? why do these formations occur where it did?
- quick clay in Norway
- area under water then once it disappeared, marine clay deposits were left behind. sodium (+) and clay (-) in ground then the fresh water leeched the salt out (compromised stability)
- triggers liquified
which glaciers are examples of continental glaciers?
ice sheets, ice caps, ice fields, ice shelves
which glaciers are examples of alpine glaciers?
valley glaciers, cirque glaciers, piedmont glaciers, tidewater glaciers
if the equilibrium line on a glacier is lower, is the glacier getting bigger or smaller?
bigger
what does the mass budget tell us?
it’s the equilibrium line -> negative vs positive mass balance
tells us about health of glacier. if negative, glaciers getting smaller
what are the names of the input/output zones on glaciers? what’s the name of the area where the glacier ends?
input: accumulation zone
output: ablation zone
ends: terminus area
what are evidence of glacial movement?
crevasses, moraines, surges
what’s that one specific glacier movement picture of?
concentric crevassing
what are examples of glacial erosion?
polished bedrock, cirques (bowls), tarns (lakes in cirques), u-shaped valleys and fjords, arêtes (2-sided ridge) and horns (3-sided), hanging valleys
what’s the deposition of material and ice by water from glaciers called?
drift
what is permafrost based on? temperature or frozen water?
temperature - at or below 0 degrees C for 2+ consecutive years
what does MAGST stand for?
mean annual ground surface temperature
define permafrost table and talik
permafrost table: upper limit of permafrost
talik: unfrozen ground within permafrost
define aggrading features vs degrading features (periglacial landforms)
aggrading: permafrost is growing
degrading: permafrost is thawing
in patterned ground, frost sorting is a combination of ___ and ______
heaving (vertical motion) and thrusting (horizontal motion)
what are pingos and how do they form?
- taliks present under large lake
- lake drains
- residual pond
- saturates soil freezes and expands up
is continuous creep slow or fast? which umbrella in mass movements is it under?
slow! flows
what is solifluction? is it slow or fast? is there a scar? what does it form? which umbrella?
- combination of frost creep and gelifluction
- slow
- flows
- no scar
- tongue-like lobes
what’s the difference. between mud flows and debris flows?
mud flows are the fastest, most fluid and most dangerous flow. fine material and water
debris are similar but contain large particles and move a little more slowly
define a slide
movement along one or more discrete failure surfaces
define active layer detachments
occur over permafrost as a result of rapid thaw of icy soils over still frozen material …. debris slides
define falls
vertical (or near) movement of particles through the air
where does blockfall principally occur?
in frozen sediments undermined by thermal erosion
what’s a complex movement? what does the nines creek photo show?
complex movement is a mixture of any of the other types of mass movements
- earthquake triggered collapse of thin ice cap & mass of ice blocks and rock fell vertically (fall)
- the mass of ice blocks and rock rushed down the valley (flow)
- debris and ice spread out (slide)
