Final Exam after midterm2 Flashcards
Describe the hydrologic cycle
evaporation --> precipitation --> runoff goes into oceans ultimately --> evaporation Total global water 96.5% oceans 2.5% freshwater (saline lakes and groundwater 1.0%) Of the 2.5% freshwater 30.1% is groundwater 68.6% glacier and ice sheets 1.3% surface water and other freshwater Of the 1.3% surface water and other freshwater snow and ice 73.1% Lakes 20.1% Other Atmosphere 0.22% Biological water 0.22% Rivers 0.46% Swamps 2.53% Soil moisture 3.52%
Identify the different parts of a fluvial system
Not in your notes
Describe the different methods of fluvial erosion and explain why erosion rates are higher closer to the head of the stream and on the outside of meanders
Headward erosion - extends the heads of the valleys upslope
Identify the difference between bedrock and alluvial channels and their different drainage patterns
Bedrock channels - are steep, winding flow. They are incised and typically at the head where slopes are the steepest Alluvial channels form in unconsolidated previously deposited sediment. They change shape with erosion, transportation and re-deposition - two common types: meandering channels (sediment in suspension, move in sweeping bends called meanders) and braided channels
Describe the two styles of flow and the factors that affect flow velocity
Laminar flow - water moving in a straight line
Turbulent flow - water moves erratically (whirlpools, eddies)
Flow velocity
Factors that affect flow velocity
1. channel slope/gradient (velocity increases in the deeper parts of the channel)
2. channel shape (cross section shape determines amount of flow in contact with the bed)
3. channel size and roughness (channels are most efficient when they are bankful, but most beds are not smooth)
4. discharge (volume of water per unit of time supplied by the drainage basin)
Describe the different methods of fluvial erosion and explain why erosion rates are higher closer to the head of the stream and on the outside of meanders
Headward erosion - extends the heads of the valleys upslope
-outside erosion is from fast moving water cutting the bank and depositing sediments on the back side where the slower moving water is located
Identify the difference between bedrock and alluvial channels and their different drainage patterns
Bedrock channels - are steep, winding flow. They are incised and typically at the head where slopes are the steepest
Alluvial channels form in unconsolidated previously deposited sediment. They change shape with erosion, transportation and re-deposition - two common types:
meandering channels (sediment in suspension, move in sweeping bends called meanders) and braided channels
NOTES do not specifically say which type of drainage pattern is associated with each. Types of drainage patterns:
1. dendritic drainage
2. rectangular drainage
3. trellis drainage
4. radial drainage
5. deranged drainage
Describe how meandering streams evolve and how stream terraces are created
Stream terraces form when a river downcuts into existing floodplain. It adjusts to new base level, forms second (third, fourth…) floodplain
Meandering streams - outside of the meander is an zone of active erosion called the cut bank. Debris acquired at the cut bank is carried down current and deposited as point bar (inside of bend)
Identify and describe four fluvial landforms shown in this section of the course
Small scale channel deposits
- point bars
Larger-scale depositional landforms
- deltas (form where sediment-laden streams lose velocity entering a lake, inland sea or ocean)
- natural levees (naturally occurring or artificial; used to regulate water levels, Is an elongated ridge, parallel to channel on both banks, Natural levees are buikt by years of successive floods)
- alluvial fans (fan shaped deposits, accumulating along steep mountain fronts.)
Describe four types of floods and the factors involved
- Regional floods - most are seasonal from spring melting and/or heavy rains. Precipitation cannot infiltrate into water-logged terrain
- Flash floods - rapid rise in water level and high flow velocities. Factors: rainfall intensity and duration, surface conditions and topography
- Ice-Jam Floods - frozen rivers are most susceptible = create ice dams across the river channel and the water upstream rises rapidly impeding flow
- Dam- Failure Floods - failure of a dam or artificial levee releases water as a flash flood
Identify and describe four fluvial landforms shown in this section of the course
Small scale channel deposits
- point bars
Larger-scale depositional landforms
- deltas (form where sediment-laden streams lose velocity entering a lake, inland sea or ocean)
- natural levees (naturally occurring or artificial; used to regulate water levels, Is an elongated ridge, parallel to channel on both banks, Natural levees are built by years of successive floods)
- alluvial fans (fan shaped deposits, accumulating along steep mountain fronts.)
Describe how glaciers form
Glaciers are large, persistent bodies of ice that form by compaction, accumulation and recrystallization of snow, that moved under own weight.
Compacting firn (granular, recrystallized snow) by >50m of overlying snow makes glacial ice.
Glaciers are found where snowfall exceeds ablation (melting and sublimation)
Identify and describe the main types of glacier
- Alpine glaciers - relatively small glaciers on mountain slopes, typically confined to valleys
- Ice sheets - larger scale >50,000km2 and are not constrained by topography, currently only found in polar loations
- Other glacial types
a) ice caps - much smaller than continental-scale ice sheets, occur at high elevations, <50,000km2 and not constrained by topography
b) outlet glaciers - are fed by ice sheets and ice caps. Tongues of ice flow down valleys that extend outwards from margins of larger ice masses
c) piedmont glaciers - occupy broad lowlands at the bases of steep mountains. Form when an alpine glacier emerges from confining walls of valley and spreads out
Explain glacier mass balance and how it affects glacier advance or retreat
Glacial budget or glacial ice balance is the balance of lack of balance between accumulation (mass of ice added) and ablation (mass of ice lost by melting, sublimation or calving)
NOTES do not explain how it affects glacier advance or retreat
Describe the two main mechanism of glacial erosion
- pucking - occurs where melt water penetrates fractures/joints of bedrock. Water freezes and expands.
- abrasion - as ice and its load of rock fragments slide over bedrock they act like sandpaper pulverizing, smoothing and polishing the surface below (forming rock flour)
Identify and describe erosional glacial landforms
1 U shaped valleys - .
2. waterfalls - higher rates of erosion in main valley means that during glacial retreat the tributary glaciers are left standing above the main glacial trough, when the ice is gone a waterfall will mark the entry of the tributary glacier into the main glacial valley
meltwater streams at the glacier margin appear milky/turquoise from suspended rock flour)
3. pater noster lakes - bedrock depressions in valley floor formed by pucking and scouring
4. cirques - small bowl shaped basins that sit at the head of a glacial valley
5. tarn - a cirque filled by a small lake
6. Fjords - deep, steep-sided inlets where mountains are adjacent to the ocean
7. Drowned glacial troughs - submerged sea level rise glacier
8. Aretes - produced by enlargement of cirques by plucking and frost wedging, have knife shaped ridges
9. horns - produced by enlargement of cirques by plucking and frost wedging, have shapr pyramid shaped peaks
10. Col - formed when two glacial troughs merge to create a pass
11. Roche Moutonnees - outcrop scale asymmetrical knob of bedrock formed when abrasion smooths the slope facing the ice sheet and plucking steepens the opposite side
