Stream and Glacial Processes Flashcards
1
Q
stream and fluvial processes include
A
- 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
2
Q
streams work depending on…
A
- discharge (Q), velocity (V), area (A)
- Q = V x A
3
Q
how do streams erode?
A
- 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
4
Q
how do streams get energy?
A
- 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
5
Q
stream characteristics
A
- excess energy stream
- balanced energy streams
- deficient energy streams
- rejuvenated energy streams
6
Q
excess energy stream
A
- 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
7
Q
balanced energy stream
A
- 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
8
Q
deficient energy stream
A
- 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
9
Q
rejuvenated stream
A
- 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
10
Q
glaciers
A
- 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
11
Q
during the last ice age…
A
- 30% of land covered
- 10% of water was ice
- Sea level dropped 100m
12
Q
characteristics of an ice age
A
- Lower than average world temperatures
- Wide fluctuations in climate
13
Q
what causes ice ages?
A
- Perturbations of earth’s orbit
- Greenhouse effect
- Plate tectonics
14
Q
perturbations in earth’s orbit
A
- causes ice ages
- Milankovitch cycles: change the amount of heat from solar radiation that any particular part of earth receives
- Tilt, wobble
15
Q
greenhouse effect
A
- causes ice ages
- Increased CO2 in atmosphere causes retention of heat, decreased CO2 decreases retention of heat
