Stream and Glacial Processes

Question 1

stream and fluvial processes include

Answer 1

• 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

Question 2

streams work depending on…

Answer 2

• discharge (Q), velocity (V), area (A)

- Q = V x A

Question 3

how do streams erode?

Answer 3

1. 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)
2. Hydraulic fracturing
3. Abrasion

Question 4

how do streams get energy?

Answer 4

• 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

Question 5

stream characteristics

Answer 5

• excess energy stream
• balanced energy streams
• deficient energy streams
• rejuvenated energy streams

Question 6

excess energy stream

Answer 6

• 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

Question 7

balanced energy stream

Answer 7

• 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

Question 8

deficient energy stream

Answer 8

• 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

Question 9

rejuvenated stream

Answer 9

• 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

Question 10

glaciers

Answer 10

• 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

Question 11

during the last ice age…

Answer 11

• 30% of land covered
• 10% of water was ice
• Sea level dropped 100m

Question 12

characteristics of an ice age

Answer 12

• Lower than average world temperatures

- Wide fluctuations in climate

Question 13

what causes ice ages?

Answer 13

• Perturbations of earth’s orbit
• Greenhouse effect
• Plate tectonics

Question 14

perturbations in earth’s orbit

Answer 14

• causes ice ages
• Milankovitch cycles: change the amount of heat from solar radiation that any particular part of earth receives
• Tilt, wobble

Question 15

greenhouse effect

Answer 15

• causes ice ages

- Increased CO2 in atmosphere causes retention of heat, decreased CO2 decreases retention of heat

Question 16

plate tectonics

Answer 16

• 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

Question 17

requirements to form a glacier

Answer 17

• 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

Question 18

how do glaciers move?

Answer 18

• Downslope

- Alpine glaciers flow downhill, continental glaciers flow outward from thickest to thinnest

Question 19

evidence of glaciation

Answer 19

• Glaciers create distinct landscapes
• Features of abrasion/erosion
• features of deposition

Question 20

features of abrasion/erosion

Answer 20

• U-shaped valley
• Fjords
• Hanging valleys
• Cirques
• Tarns
• Aretes
• Horns
• Glacial polish
• Striations, grooves
• Rock flour

Question 21

u-shaped valleys, fjords, hanging valleys

Answer 21

• 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

Question 22

cirques and tarns

Answer 22

• 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

Question 23

aretes

Answer 23

• features of abrasion/erosion

- Knife edge ridge, often between 2 glaciers

Question 24

horns

Answer 24

• features of abrasion/erosion

- Sharp peak that would have stuck out above the glacier

Question 25

rock flour

Answer 25

- feature of abrasion/erosion | - finely-ground material deposited into lakes -> causes turquoise colour

Question 26

features of deposition

Answer 26

- Glacial drift (tills and outwash) - Moraines - Kettle - Esker - Drumlin - Erratic

Question 27

glacial drift

Answer 27

- feature of deposition - general term for all sediment derived from glaciers - - Tills: poorly-sorted, unstratified, hummocky (form mounds) - - Outwash: sorted and stratified

Question 28

morraines

Answer 28

- feature of deposition - till carried/pushed along by glaciers and deposited at edges of glacier - 4 types: end, lateral, medial, ground

Question 29

kettle

Answer 29

- feature of deposition | - small hole in till where a piece of ice was while sediment was being deposited, usually filled with water

Question 30

esker

Answer 30

- feature of deposition | - positive relief feature made from sedimentation in drainage channels at base of glacier

Question 31

drumlin

Answer 31

- feature of deposition | - wedge-like mound of till showing ice movement direction

Question 32

erratic

Answer 32

- feature of deposition | - large exotic rocks carried long distances from their origin by the ice, then dropped once ice melts (ie. White Rock)