Final Exam
berm
"bench" in elevation on beach (mound)
cirque
"bowl" carved by the base of a glacier through erosion
surging wave
"kind of like a slump"; occur on the steepest beaches, with smooth wave faces
Primary Coasts/Type 1 Coasts
"non-marine formed shorelines" such as glaciation, stream deposition from deltas, fluctuating sea levels, active volcanism, or organic coasts (reefs, mangroves) "primary fingerprint is NOT oceanic wave action"
roche moutonnee
"rock mountain" formed by glacial erosion; the glacier passing over bedrock causes an asymmetrical form as a result of abrasion on the sloss side and plucking on the lee side; it is smooth in the direction of ice movement
translatory motion
"up and over" towards shore; re-suspends sediment
distribution of heat to the ground due to slope and direction of slope towards sun
(think of the lab where we figured out the glaciers were retreating one way due to the ridge and the path of the sun throughout the day) wet N-facing slope: active layer, colder, permafrost present, freeze/thaw important dry S-facing slope: permafrost missing, freeze/thaw not as important, warmer -----> different ecologies and geomorophologies
filling of tidal inlets
1. streams bring sediment to coast 2. coastal bay becomes filled with sediment as outlet becomes blocked by bar 3. tidal inlets completely filled in, coast straightens, streams diverted elsewhere
migration of barrier islands
1. tidal currents enter inlet 2. inflowing tidal currents deposit sediment in lagoon, sediment builds up behind barrier island; high energy in front of barrier island, low energy behind barrier island 3. barrier island migrates landward and shoreline retreats, so lagoon is same size as before (inlets naturally heal up, years later it will naturally be destroyed again)
Glacial Budgets
A valley glacier could appear at the end of a melt season. Below the snow line, glacier ice and snow have been lost during the melting season. In the zone of accumulation above that line, firn is added to the glacier from the previous winter fall.
Why are there sandy beaches on the east coast and rocky beaches on the west coast?
Active tectonics on the west coast (erosional features) Passive tectonics on the east coast (depositional features)
frost sorting theory 1: Frost Pull
Ground freezes from the top down --> the top of a large pebble is gripped by ice and rises upwards --> lateral pressure causes sediment to slump into the cavity where the pebble used to be --> pebble cannot return downward (this happens multiple times until it is brought to the surface)
Ingredients for making glaciers
Land Snow ***COLD SUMMERS*** Gravity Time
Secondary Coasts/Type 2 Coasts
MARINE PROCESSES ongoing marine erosion and deposition; marine processes are stable for long enough that marine fingerprint overcomes type 1 (non-marine) fingerprint
Relate black/green sand beaches and bowen's reaction series
Mafic minerals compose black and green sand beaches. They are rare because there must be a fairly active volcano near since mafic minerals have low resistance to weathering so continuous deposition of these minerals is needed to maintain black/green sand beaches.
thaw lakes
NOT KETTLES!!! product of thermokarst (polygonal patterns is clue that it is thermokarst and not kettles)
mima mounds
NOT a periglacial landform...just looks like it (look like palsas)
tombolo
When the mainland is attached to an island by a narrow piece of land such as a bar or a spit ("depositional bar behind sea stack because sea stack is being eroded")
icebergs
a block of ice that came from a glacier and is floating in water
collapsing wave
a combination of plunging and surging waves
rock-basin lakes (tarns)
a lake occupying a depression caused by glacial erosion of bedrock
Rayburn's definition of glacier
a large, long-lasting mass of ice, formed on land that moves under the influence of gravity and its own weight
jettys
a pier constructed to keep inlets clear
rock flour (glacial erosion)
a powder of fine fragments produced by the grinding of rock across rock; polishes rock surface; essentially silt and clay sized grains jumbled up
paternoster lakes
a series of circular lakes, formed by glacial erosion, that occur in formerly glaciated valleys
medial moraine
a single long ridge of till on a glacier, formed by adjacent lateral moraines joining and being carried down-glacier; "run right down the center"; tend to show 2+ glaciers next to each other that got together
hanging valley
a smaller valley that terminates abruptly high above a main valley; can make waterfalls
baymouth bar
a spit that covers access to a bay since the area behind it fills with sediment
kame terrace or kame moraine
a terrace made of sorted sediment deposited by meltwater streams that formed against a previous ice margin
riprap/seawall
a wall of stones that protects shorelines
glacial erosion under the glacier
abrasion and plucking, bedrock polished and striated, rock flour washes out of glacier, polishing and rounding, striations on rock
open system pingos
all about groundwater slower need enough pressure from groundwater flow to keep feeding the system "icy magma chamber from regular GW flow" discharge and recharge groundwater keeps feeding the central ice core
stream deltas
alluvial (river) processes; delta is riverbed building itself out to sea level
Ice is...
always moving forward and we're always shedding material off the front even it its advancing
erratic
an ice-transported boulder that came from somewhere else not nearby
periglacial landforms (what do you need?)
annual average temperatures below freezing, land, and non-glaciated
ogives
annual markers of ice flow (distance between them is annual movement of ice) "an alpine glacier thing" ogives begin at the knickpoint, each "U" represents one year of movement over the knickpoint darker pattern in these is due to higher concentration of dirt from melting at thinner ice (usually in warmer months) the center of the ice gets ahead of the edges
foreshore
area between high and low tide
mountain landscape features after glaciation
aretes horn cirque rock basin lakes (tarns) rock step hanging valley U-shaped valley
mountain landscape features during glaciation
aretes horn truncated spurs glacier triangular facets
glacier cross section
as you go deeper, density increases plastic deformation (permanently deforms glacier) behavior is different for ice sheets vs. alpine glaciers (alpine not as thick, density increases with little depth)
backshore
between high tide and where the storm can reach
kettle
big holes in outwash caused by the melting of a block of ice that was surrounded by sediment
plucking (glacial erosion)
bits of other rock in ice can erode underlying rock, which can be picked up by the ice due to the PMP; pressure on the boundary between the bedrock and ice can break off bedrock
ground moraine
blanket of till deposited during glacial retreat
drumlins
bodies of till shaped into smooth hills; direction of ice flow is in direction where the long axis "points" towards (ex: in this picture ice flow direction is -->)
block field/"felsenmeer"
boulder fields that are/have been actively moving on almost no slope whatsoever "a river of slow-moving boulders"
valley train
braided outwash that travels down a valley
human impacts on coastlines
break waters, groins, and jettys all cause deposition of sediment somewhere; development destroys vital shoreline vegetation; water and petroleum pumping cause problems
disruption of ice
can cause significant ground collapse --> loss of habitat
rock glaciers
can result from 2 processes: 1. (glacial) glacier nearly melts away --> leaves only rocks 2. (periglacial) permafrost area. mass wasting --> sorted pile of rocks --> freeze/thaw results in a pile of rocks on a slope
Tides
caused by gravitational forces of sun and moon
u-shaped valley
characteristic cross-profile of a valley carved by glacial erosion; "in equilibrium with geometry of ice"; glacier is more viscous and "domes up" and focuses energy across wider area to form these
headlands
cliffs that jut into the sea
frost sorting theory 2: Frost Push
cold penetrates into the ground --> large stones have ice formed around them faster than surrounding soil (due to stone having greater thermal conductivity) --> stone is forced upwards --> sediment slumps into cavity where stone was (this happens multiple times until it is brought to the surfacce)
flood tides
coming in (to shore)
biological processes- coral reefs
corals try to keep up with sea level since they need to be in an area where light can penetrate the water column
brittle deformation
cracking and moving
ice: hexagonal crystal system
crystal structure like a mineral, ice IS a mineral. have one long axis (c-axis) and multiple short axes (a-axes) much easier to deform along short axes (a-axes)
longshore current
current produced as water flows parallel to coastline
hook
curved spit created when there is a secondary wind
intragranular shifting (glacier movement)
deformation along crystal axial plane occurs if its freezed into ice; you need sufficient pressure for this
formation and growth of glaciers
diagenetic process; fluffy flakes pile up and have lots of air in them, they are not dense, but if you keep piling snow up then the snow will be altered from pressure to a more dense state
intergranular shifting (glacier movement)
differential movement between ice grains occurs if the grains aren't that "locked" or "fused", like firn (lower pressure situation)
lunate fracture or crescentic gouge
direction where gouge gets deeper is direction of ice flow
lateral moraine
elongate mounds of till which form along the sides of a valley glacier
fjords
elongated, deep and narrow sea amid steep land; a U-shaped undersea valley surrounded by mountains; longer than it is wide
Wave refraction with uneven shorelines?
erosion where it sticks out (headland), deposition in beaches (where it goes back; see pic in notes)
continental glaciation
exists where a large part of a continent is covered by glacial ice
closed system pingos
faster, rapid ground underneath is talik (thawed) lake drains somehow --> saturated unfrozen ground exposed to cold temps --> freezes and expands --> suddenly grows
glacial flow
fastest ice motion occurs at the surface near the center of the glacier (least amount of frictional drag)
Albany Pine Barrens (field trip, state glacial history)
fine sand; parabolic dunes; low pressure system has winds moving in counterclockwise fashion to create these; climate was dry, windy, and had little vegetation when the dunes were created; shallow lacustrine (lake) deposits (well-sorted sand); LAKE ALBANY WAS HERE!--> lake regressed--> only sand after drying out, no vegetation; this dune likely formed shortly after glacial Lake Albany retreated because that is when plants began to establish
spit
finger-looking ridge of sand deposited where longshore drift encounters deeper water
sea arch
forms when two sea caves erode completely through the headland
alpine glaciation
found in mountainous regions; VERY sensitive to climate change
glacial erosion above glacier
frost wedging, erosion by glaciers steepens slopes
stone circles
geometric patterns of sediment that are naturally occurring
faceted (glacial erosion)
given a flat surface by abrasion
glacial outwash
glacially eroded, sorted sediment that has been transported by meltwater typically, the sediment becomes finer grained with increasing distance from the glacier terminus (sand, silt, clay farther downstream and coarser grained sediment closer to the glacier) (subglacier=till, midglacier=gravel, further away=silt and clay) (the only way dropstones end up in silt and clay lake deposits are if it came from an iceberg)
formation of kettles
glacier retreats and leaves behind chunks of dead ice --> heat melts the glacier and outwash is carried down the glacier --> outwash flows over the dead ice and forms a new layer of ground --> the dead ice continues to melt until they're completely gone --> kettle formed (outwash is still there and makes up sides of kettle)
isostatic rebound
glaciers cause rebound by causing depressions --> glacier retreats --> land rebounds (trying to reach equilibrium); causes a "smear of raised beaches"
Where do glaciers develop?
glaciers develop where all of the annual snow doesn't melt away in the summer (polar regions, heavy winter snowfall, high elevations, 85% in Antarctica, 10% in Greenland)
eustatic sea level change due to glaciers (CLIMATE)
glaciers lower sea level slowly glaciers melt quickly and sea level rises
receding glaciers
glaciers with negative budgets that grow smaller and their edges melt back
advancing glaciers
glaciers with positive budgets that push outward and downward at their edges
ebb tides
going out (to ocean)
permafrost
ground frozen throughout the year
passive continental margins
have broad continental shelves and beaches with spit
snow line
height above sea level where glacier is at equilibrium; equilibrium line; ELA (equilibrium line altitude, point at which accumulation=melting)
Ice always moves from ____ to ___ pressure
high; low
features of glaciers game link
https://www.purposegames.com/game/features-of-glaciers-game?l=14754
Stop 4 (field trip, state glacial history)
huge wall of clay, inside of wall near bottom are varves of fine sand and clay repeated with random large rocks; as you go up side of cliff, layers get smaller and smaller; proglacial lake depositional environment; as ice retreats we get less and less deposits --> smaller varves
chatter marks/crescentic fractures
ice frozen onto bed puts stress on rock A series of small, closely spaced, crescentic grooves or scars formed in bedrock by rocks frozen in basal ice as they move along and chip the glacier's bed. The horns of the crescent generally point down glacier.
Morphology (glacier classification)
ice profile and topography -alpine: controlled by topography -ice sheet/ice cap: independent of topography; moving out from a central location -piedmont: alpine glacier that flows onto flat area and spreads out; "combination of alpine and ice sheet"; "fans out, and the fan behaves like an ice sheet, an alluvial fan of ice at lower elevation, and behaves like an alpine at high elevation"
sea stack
if top of arch collapses, it leaves a single column
stone stripes
in areas where the ground is on a slope, these are caused by gravity where material is moving downslope in waves; "soil creep through freeze/thaw and permafrost slopes" (doesn't take much of a slope to occur)
wave dispersion
in deep water, longer waves travel faster than shorter ones and will gradually leave the shorter ones behind; "they sort themselves out on their way to shore" (this is why on the beach near the shore the waves are short and why they're long further into sea, due to depth!)
pro-glacial
in front
eustatic sea level change due to mid ocean ridges (CLIMATE)
increase in MORs --> increase in temp of water --> sits higher up in asthenosphere --> increase in sea level (isostasy) sea level drops if activity slows and MORs become smaller
fringing reef
initially surround land, grow seaward
thermokarst
karst topography formed by melting of ground ice underlain by permafrost (ground collapses) (looks like a sinkhole); freeze/thaw is a big player in physical weathering in active layer and above (sharp boundary between active layer and permafrost)
Gravel Pit (field trip, state glacial history)
lake deposits over pre-existing glacial deposits (glacier-->deep lake-->shallow lake); clay under well-sorted medium sand indicates depositional environment of deep lake to shallow lake to shoreline (glacial geomorphology with coastal processes); REGRESSION OF LAKE ALBANY; well-sorted sediment indicates high energy fluvial environment; kame deposits and kame terrace indicate high energy, lots of water, and lots of sediment; esker deposit indicates fluvial under glacier
palsas
like pingos but much smaller and occur in groups in boggy areas bogs form --> freeze --> trap organic gases (ex: methane) --> if it melts, those gases are released (positive feedback climate issue) thick vegetation and organic matter regulates the soil temperature --> small individual blocks of ice that grow in places where there's positive pore water pressure
atoll
little circular reef island where volcano used to be
esker
long sinuous ("snakey") ridge of water-deposited sediment (common with ice sheets) (formation of this is usually perpendicular to recessional moraines)
terminus
lower edge of a glacier; at the end of glacier; the ice margin IN THE DIRECTION WHERE ITS MOVING
biological processes- mangroves
mangrove stands; mangrove forests have trees that are adapted to saltwater
Dynamics (glacier classification)
mass balance (the balance between accumulation and ablation) -advancing: positive mass balance -stagnating: negative mass balance -neutral: equilibrium mass balance; terminus and ELA are staying in place (related to climate, can change)
outwash
material washing out from glacier that's full of sediment (transported by meltwater)
Airy Equation
mathematical equation to describe wave movement in different water depths if depth decreases --> velocity decreases and wavelength decreases --> height increases (H:L ratio. higher ratio --> steepened waves --> waves crash; has to do with angle of repose)
recrystallization (glacier movement)
melting and refreezing of ice crystals, related to Pressure Melting Point
Modern glacier distribution
mostly limited to polar regions most of the Earth's freshwater is bound up in Antarctic Ice Sheet
pingos
mound made in permafrost areas where the center is a big block of ice; pingo grows as ice block in center grows
plastic flow
movement that occurs within the glacier due to the plastic/deformable nature of the ice itself; cold-based glaciers usually, dependent on pressure
Glacier
must be on land, must have ice, and ice must be "alive" (actively deforming) --> moving under gravity from its own mass
Northern hemisphere polar ice
not a glacier because it is not on land
spilling wave
occur on gently sloping beaches, where the crest breaks and spills down the face of the wave
extending flow
occurs when the gradient of the underlying rock surface steepens and the glacier responds by accelerating and becoming thinner; this can happen over knickpoints
compressive flow
occurs when there is a reduction in the subsurface gradient and the glacier slows down and thickens due to the build up of ice (upwards movement)
eustatic sea level change due to ocean temperature (CLIMATE)
ocean water can thermally expand or contract
transverse crevasses
ogives; bending across ice fall
superglacial
on top
crevasses
open fissures (cracks) in a glacier caused when it passes over a steep part of the valley floor and moves faster than the upper part of the rigid zone of ice which cannot stretch to move as rapidly as the underlying ice. Being brittle, the ice of the rigid zone is broken by tension/normal stress; they only go down to where the brittle/plastic boundary is
moraine
pile of glacial sediment that marks the end of ice; "till as a landform"
human-induced problems with melting permafrost
pipelines thaw out ground beneath them (from providing heat to keep the material being transferred viscous to flow) railroad tracks can warp landscape significantly heat in buildings transfers to ground--> destabilizes ground --> destruction
divergent/convergent plate boundaries
possess steep continental shelves
frost sorting
preferentially bringing the bigger material to the top by the freeze/thaw process; grain-size sorting
wave-cut bench
produced when waves undercut headland
end moraine
ridge of till piled up along the front edge of a glacier; the outermost end moraine
truncated spurs
ridges that have triangular facets produced by glacial erosion at their lower ends
sea cave
rock was weak --> physical erosion --> sea cave (produced when waves are refracted against the side of headland)
mountain landscape features before glaciation
rounded ridges rounded peaks V-shaped valley
striations (glacial erosion)
scratches in the rock in the direction of ice movement
gelifluction
seasonal freeze-thaw action upon permafrost soils which induces downslope movement (causes stone stripes)
barrier reef
separated from coast by a lagoon
Cohoes Falls (field trip, state glacial history)
shale and greywacke (not too structurally sound); waterfall has not moved at all in complete historical documentation--> knick point must have been carved under a much higher discharge regime (Mohawk cannot provide this, so it must have formed during the time of the Iro-Mohawk); Mastodon found here is key to the timing (as the pothole it was found in couldn't have formed until this waterfall was forming)
arete
sharp ridges that separate adjacent glacially carved valleys
tectonic uplift
sharper than isostatic rebound; causes uplifted coastal terraces
flute
small ridge protected by a rock from glacier/water that shows direction of ice flow; long, linear ridges; sub-glacial landform
Snow to Ice
snowflakes--> granular snow --> firn (in between snow and ice) --> glacier ice (fusion of grains, density of ice is reached) almost like going from a sand to a sandstone (due to fusion and increase of density of particles)
where do drumlin fields occur?
somewhere near the end of the ice margin
wedges
splitting apart frozen ground through time due to freeze/thaw (they just grow and grow and grow; positive feedback)
radial crevasses
spreading in all directions; piedmont glaciers
beach
steepest part of the foreshore
groins
structures designed to trap sand as it is moved down the beach by the longshore drift; stabilize beaches (but also cause erosion on the opposite side, where sand is not being trapped)
kame deposit
superglacial deposit; a lake was held in place by ice on both sides which then melted and left deposits (ice was previously holding deposits in place)
local sea level change (TECTONICS)
tectonics can raise or lower local sea level glacial isostatic equilibrium changge can raise or lower local sea level
Pressure Melting Point
temperature at which ice melts at a given pressure with enough pressure, a solid can turn into a liquid by pushing the molecules close enough together, once the object is liquid, you can lose resistance to flow that the solid object has, then you can easily move (this usually happens at the bottom of the glacier); once it moves, pressure is released and it becomes solid again
Thermal (glacier classification)
temperature of the ice relative to PMP -temperate: ice is at or near PMP "wet based glaciers"; slides easily -polar: ice is below PMP most of the time "cold based glaciers"; requires plastic deformation for ice to move -sub-polar: ice is always below PMP "frozen based glaciers"; only moves through inter-/intra-granular deformation. ONLY plastic deformation (related to climate, can change)
chevron crevasses
tension
talik
thawed area due to variations in insolation (because of things like vegetation, presence of open water, or albedo of rock/vegetation/water/etc.)
zone of wastage
the lower part of the glacier where ice is lost or wasted by melting, evaporation, and calving (split and shed); where losing > gaining; zone of ablation
tidal bulges
the moon's gravitational field attracts water to the side of earth nearest it, creating a high tide on the side of the Earth nearest it, and a corresponding bulge on the opposite side. The areas between the bulges repel the water, leading to low tides
negative budget
the opposite of positive budget (amount of ice and water lost is greater than amount of snow gained, glacier recedes) (margin recedes)
South Pole
the physical pole placed here is no longer exactly at the south pole because the ice is moving, therefore the south pole is a glacier
horn
the sharp peak that remains after cirques have cut back into a mountain on several sides
basal sliding
the sliding of the glacier as a single body over underlying rock; low friction; usually with warm-based glaciers "slides on the base"
frost heave and formation of stone circles
the soil and stones move upwards due to ice crystals and frost heave --> the soil moves downwards due to melting but ice crystals beneath the stones stop them from returning to their original position --> uneven heating and cooling causes the ground to rise up "as a frozen bubble" and stones roll down to the bottom of the slope --> formation of stone cirlces
Ice sheet
the thickest part of a glacier is where the most precipitation is; the ice flows in all directions (think of pouring syrup on a table)
rigid zone
the upper part of the glacier where ice grains are locked and move together
collapsed pingo
thermokarst lake with ring around it
varve
two thin layers of sediment, one dark (silt/clay) and one light (sand) representing one year's deposition in a lake (if each couplet represents a year--> seasonal variations)
sub-glacial
under
ablation/wasting
under the influence of gravity, glacier ice moves downward and is eventually lost of wasted
till
unsorted and unstratified glacial sediment deposited by glacial ice
oscillatory motion
up and down (deeper water)
zone of accumulation
upper part of the glacier with a perennial (enduring) snow cover; where mass is gained
movement of valley glaciers
valley glaciers move downslope under the influence of gravity and their own weight
wave refraction
velocity of wave slows down as it gets closer to shore due to friction --> waves come in having crests nearly parallel to the coast ("you slow down water waves and this changes the angle at which it travels")
rip current
water pools up, enough mass of water builds up and it "rips out" into the ocean quickly and powerfully
ice wedge polygons
wedging out polygons of frozen ground
plunging wave
well over the angle of repose; more erosion occurs because energy is focused over a small area (occur where the beach is steeper, and are characterized by a steep wave face with the crest curling over the top)
positive budget
when the amount of snow a glacier gains is greater than the amount of ice and water it loses and it expands (margin advances)
brittle/plastic transition
where flow begins and brittle deformation (crevasses) end
longitudinal crevasses
widening; spreading width
What does the nature of waves depend on?
wind velocity wind duration fetch (length of water over which a given wind has blown)
τ=ρgt sinα
τ= critical shear (constant) ρ= density of ice (constant) g= gravity (constant) Given perfectly plastic deformation with a constant yield stress of 1 bar: t sinα=τ/ρg OR 1/ρg=t sinα= Constant (if slope increases then thickness decreases; ice going over an ice fall will thin due to an increase of slope, this increases the likelihood of deep crevasses)