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66 Cards in this Set

  • Front
  • Back
3 major points about glaciation
Ice flow
Glacial landforms
Periods of glaciation
Ice flow: ice in glaciers is like what type of rock?
Metamorphic rock, recrystallized by pressure and temperatures close to melting, deformed by intra-crystalline creep
Glaciers flow in directions based on their...not based on their...
What do temperate glaciers slide on?
Surface slopes, not their basal slopes
Their bases
Glacier definition
A mass of ice large enough to flow under the influence of gravity
Glacial cover and mass balance process
On cirque accumulation of snow, cold
On toe less snowfall, warmer
What is mature ice like? (effect of recrystallization)
Dense with little air
Burial by later deposits causes shear stress, proportional to... (2)

Stress+heat+time=?
Surface slope and depth

Plastic flow
When does plastic flow occur?

Plastic flow makes ice viscous, so it flows...
Greater than 60% of the melting temp in K (for ice=-164 deg and all glaciers are warmer on Earth)

downhill by deforming internally
Ice deforms tremendously during flow, first stretching in zone of accumulation then shortening in zone of ablation
What does the zone of ablation look like
Dirty, melting ice reveals rock debris that was distributed through the ice
Describe visual process
Snow accumulation on the cirque, flows downhill to the toe/zone of ablation where summer melting exceeds winter snowfall (after equilibrium line attitude)
Despite flowing faster, toe position can retreat if..
Supply of ice is reduced
Erosional landforms-how do all glaciers and temperate glaciers erode
Glaciers erode by plucking blocks of jointed bedrock
Temperate glaciers also erode by abrasion using included rocks as tools
Temperate glacier erosion rates are proportional to...forcing valley floors to become...
Ice velocity times ice thickness
Semicircular (U-shaped)
Depositional forms
Glaciers also build constructive depositional landforms, such as end moraines
Glacial striations
scratches or gouges cut into bedrock by glacial abrasion
Before glaciation
During glaciation
After glaciation
Mountain river cuts a V-shaped valley
Cirques and toes form, U-shaped valley
Tributary valley as left as a hanging valley
What are fjords?
U-shaped glacial valleys whose bottoms are hidden by the sea
Glaciers can cut below current sea levels down to a depth of about?
80% of ice thickness
What is a small glacier? When melted there is a...
Cirque glacier
Lake or tarn
Nunatak
isolated bedrock outcrop protruding from a continental icecap
Depositional landform - moraine, outwash
Sediment transported by ice
Fluvial deposits typically braided rivers
Till
Ice deposited, many grain sizes mixed together
Recessional moraines
Formed by temporary stand-still of receding terminus
Lateral and medial moraines location
Material dropped onto glacier by...(3)
To side, in middle
Rockfall, landslides, avalanches
Ground moraine
Semi-continuous cover of till
Dead ice
Drumlins
Forms kettle holes
Streamlined mounds of till
Esker
Varve
Deposit from river within or beneath ice
Annual band in lake deposit
Kame Terraces
When the glacier melts...
Stratified deposits laid down ON the glacier by melt streams or beside the ice

They are dumped roughly
Lake deposits record history in annual...
Varves (fine-course sediment bands)
Past glaciation evidence-erratics
Lakes bounded by...
Rocks different from the bedrock on which they now rest
Striking end moraines and lateral moraines composed of till
Variations of (hebrew L)18O of marine forminifera show...
Size of land-based glaciers back through time
Cold periods are...
When was the last glacial maximum?
Gradual cooling under...
Glaciation
20,000 years ago
Shorter fluctuations
Variations in (hebrew l)18O gives...
Precipitation temperature
Relative dating until 1940
Placed rocks into named eras, periods and epochs in a universal time scale, based on superposition, inclusion, etc.
Absolute or radiometric dating
Uses radioactive decay of an unstable isotope as a clock, read by measuring conc. or parent and daughter isotopes
Stratigraphic and radiometric dating methods combined provide
A quantitative history of the evolution of life
In a stack of undeformed sedimentary beds...
age increases downward
First early attempts to name the periods referred to...
lithology/rock-type of sediments
Better system was devised that put emphasis on...
fossils
William smith
Observed association of fossils with formations
Created the first statigraphic column
Made the first geologic map
Smith's advance in geology and how it relates to Darwin
Groups of fossils occur in the same order everywhere in the world, could be determined for sedimentary rocks that did not touch one another
Branches can diverge, converge, or end BUT they never recombine
Mass extinctions form
A convenient boundary
Geologic groups applied to fossil groups and then transformed into the names of...
Geologic periods
Unconformity
limestone/sandstone that is younger than the bedding surfaces in the sandstone
Unconformities are not the only cross cutting surfaces, others include...
Intrusions, faults, folds, soil horizons, erosion surfaces
Most easily interpreted dates from...
Can be reasonably sure the age of the mineral is close to the age of...
Fine-grained igneous rocks
The volcanic event
Boundary most studied is...
the Cambrian radiation or "explosion"
Hard body parts expanded...
The fossil record from the Cambrian
Animals with no hard parts from the...
Precambrian
Metamorphic rocks record what kind of history?
Down-then-up history
Bobs down then up and pulls up stuff with it
(subduction of buoyant continent down then isostatic rebound)
Continent subducts beneath oceanic crust, the oceanic crust will be uplifted as..
An ophiolite suite
If a continent subducts beneath a continent then...
Former site of the ocean is marked by a suture
Double-thick crust is form, which supports 5km topography
Suture
Deformation (orogeny) spreads across both continents until...
The plates finally stop
Subduction can recycle old seafloor indefinitely but cannot swallow...and struggles to consume...
A whole continent
A young seafloor
Metamorphic rocks that leave rocks on the surface are caused by...
Subduction of a buoyant cont, an end to subduction, then isostatic rebound linked with erosion
If a buoyant cont is pulled into a subduction zone by a dense slab of seafloor lithosphere, subduction will stop after...
Consuming only one edge of the continent
Dense slab of seafloor lithoshere tears off, continent released and will...
Spring upward, lifting the crust of the overriding plate into the air
If a cont subducts beneath oceanic crust, oceanic crust will be uplifted as...
An ophiolite comprising bedded chert, pillow basalts, sheeted dikes, gabbro, peridotite
Ophiolites include scattered Cu/Mn ore deposits, now recognized as...
Cyprus=cuprous=?
Black smoker hydrothermal vents
Copper
Inactive thrust fault with scraps of ophiolite (former seafloor) and turbidites (trench deposits) are...
This is formed when
Sutures
2 smaller continents drifted together
Youngest continental collision, From Pliocene-now; Arabia/Eurasia
What does seismicity show?
Zagros
Subduction has stopped
Next youngest continental collision, from Eocene-now, in India/Eurasia
Himalayas/Tibet
Next youngest continental collision, From Cretaceous to now in Europe/Africa, also the longest running active continental collision
Alps of Europe
Next youngest, from Pensylvanian-Permian, Europe/Asia
Urals, inactive "dead"
Erosion has removed the mountains many times, but isostasy causes them to rise...
less each time since the crust is thinner than before
Next youngest, from Pennsylvanian-Permian in Laurentia/Gondwana
Carbon copy of the urals