Stream and Glacial Processes Flashcards
stream and fluvial processes include
- Includes hydrologic cycle (water cycle), rock cycle (weathering, erosion, and transport of material from mountains to the ocean – recycling of minerals into new rocks)
- Important because streams erode, transport, and deposit sediment all at the same time to form landscapes
streams work depending on…
- discharge (Q), velocity (V), area (A)
- Q = V x A
how do streams erode?
- Dissolution
- - Dissolved load (need to test to see it)
- - Suspended load (fine particles like silt, muddy-looking)
- - Bed load (large particles and rocks rolling and sliding) - Hydraulic fracturing
- Abrasion
how do streams get energy?
- from slope and discharge
- A = “graded” (equilibrium) stream profile and base level
- Stream gradient (m/km or ft/mile): changes in elevation over distance; varies along profile
stream characteristics
- excess energy stream
- balanced energy streams
- deficient energy streams
- rejuvenated energy streams
excess energy stream
- Erosion > deposition
- High energy stream carrying lots of load – cuts vertically into the landscape
- Unstable material collapses into stream, increasing load and erosive power
- V-shaped valley
- Straight channel stream
- Rapids and falls
- Youthful down-cutting stream
balanced energy stream
- Erosion = deposition
- Starts as youthful downcutting stream, then meanders and undercut the valley wall (lateral erosion)
- Have well-developed flood plain
- Features: cutbacks and point bars (deposits) indicate lateral erosion
- Variations in stream velocity cause erosion
- Maximum velocity near outside edge of meanders
- Erosion happens on outside edge -> ( (, deposits happen on inside edge -> ) )
- Eventually can cut off meanders to form Oxbow lakes
- Mature, moderate graident, no rapids
deficient energy stream
- High energy streams exit the steep mountains and lose energy
- They can no longer carry the load they have so they rapidly deposit the largest grain sizes and form braided rivers or channel
- At its base level, a stream loses all capacity to carry load and deposits everything, forming an alluvial fan or Delta
- Low gradient, varying ages
rejuvenated stream
- Tectonic influence on streams -> change in base level leads to rejuvenation and excess energy -> downcutting and stream terraces
- Entrenched meanders
- Meanders = sweeping curves
- Meanders are more exaggerated with age -> then forms oxbow lake, cuts off, and is straight again
- High gradient
glaciers
- permanent mass of ice that flows downslope under the influence of gravity
- Form in periods of cool climate
- Four ice advances in last 2 million years (with average temp drop of 5-10 degrees C)
- Today they cover 10% of earth’s continental surfaces
- Tie up 2% of earth’s water
- If all glacial ice melted, sea level would rise about 60m
during the last ice age…
- 30% of land covered
- 10% of water was ice
- Sea level dropped 100m
characteristics of an ice age
- Lower than average world temperatures
- Wide fluctuations in climate
what causes ice ages?
- Perturbations of earth’s orbit
- Greenhouse effect
- Plate tectonics
perturbations in earth’s orbit
- causes ice ages
- Milankovitch cycles: change the amount of heat from solar radiation that any particular part of earth receives
- Tilt, wobble
greenhouse effect
- causes ice ages
- Increased CO2 in atmosphere causes retention of heat, decreased CO2 decreases retention of heat
plate tectonics
- Volcanic eruptions can temporarily cool down planet
- Rates of plate movement
- Positions of continents (Albedo effect -> oceans absorb heat while continents reflect heat away, especially when close together)
- Effect on ocean circulation
requirements to form a glacier
- Accumulation of snow in winter > melting of snow in summer
- Compaction of accumulated snow -> ice
- Ice must flow down slope
- These requirements are satisfied at high latitude or high elevation locations
how do glaciers move?
- Downslope
- Alpine glaciers flow downhill, continental glaciers flow outward from thickest to thinnest
evidence of glaciation
- Glaciers create distinct landscapes
- Features of abrasion/erosion
- features of deposition
features of abrasion/erosion
- U-shaped valley
- Fjords
- Hanging valleys
- Cirques
- Tarns
- Aretes
- Horns
- Glacial polish
- Striations, grooves
- Rock flour
u-shaped valleys, fjords, hanging valleys
- features of abrasion/erosion
- u-shaped valley formed by large glaciers slowly grinding out the valley
- fjords: u-shaped valleys filled by the ocean
- hanging valleys: small u-shaped valleys that were carved out by tributary glaciers – hanging as they sit above the valley floor
cirques and tarns
- features of abrasion/erosion
- cirque: Steep-sided amphitheatre-like feature at the head of a glacier
- Tarns: Lake sitting within a cirque once the ice has melted away
aretes
- features of abrasion/erosion
- Knife edge ridge, often between 2 glaciers
horns
- features of abrasion/erosion
- Sharp peak that would have stuck out above the glacier
rock flour
- feature of abrasion/erosion
- finely-ground material deposited into lakes -> causes turquoise colour
features of deposition
- Glacial drift (tills and outwash)
- Moraines
- Kettle
- Esker
- Drumlin
- Erratic
glacial drift
- feature of deposition
- general term for all sediment derived from glaciers
- Tills: poorly-sorted, unstratified, hummocky (form mounds)
- Outwash: sorted and stratified
morraines
- feature of deposition
- till carried/pushed along by glaciers and deposited at edges of glacier
- 4 types: end, lateral, medial, ground
kettle
- feature of deposition
- small hole in till where a piece of ice was while sediment was being deposited, usually filled with water
esker
- feature of deposition
- positive relief feature made from sedimentation in drainage channels at base of glacier
drumlin
- feature of deposition
- wedge-like mound of till showing ice movement direction
erratic
- feature of deposition
- large exotic rocks carried long distances from their origin by the ice, then dropped once ice melts (ie. White Rock)
