• Deposition
• Destructive metamorphism
• Sintering (firn)
• Compaction
• Cementation

glacial mass balance

budget=gain-loss

gains=snow in zone of accumulation

loss=zone of ablation

budget can be:

• positive (net growth, advance)
• Static
• negative (net melting, retreat)

• snowfall
• wind blown snow
• refreezing summer rain

glacial ablation includes

• melting
• sublimation
• evaporation
• calving

ELA

Equilibrium line altitude

• above ELA: net snow accumulation
• below ELA:net snow loss- this is ice

2 types of glacial flow

1. internal deformation
2. basal sliding

• glacier frozen to bed
• driven by deformation (creep)
• glacier moves slowly
• sliding velocity is zero

• melted water at the bed
• basal sliding
• can slide over bed quickly by 
• can deform internally

basal sliding rate (V_b) & internal deformation 

V=VI+V_b

1. unconstrained by topography
2. ice cap (or dome)
3. tidewater (or outlet glacier)

Alpine glacier (mountain valley)

[image]

• topographically constrained by cirques and valley walls

Ice field (mountain range)

[image]

• occupy highlands and can bury existing topography
• drained by outlet glaciers

ice sheet (continental scale)

[image]

• largely overwhelm topography
• ice buries peaks
• surface slope controls ice flow direction

• ice flow dominated by surface slope of glacier

• a floating ice cap or part of an ice sheet only partially constrained by the coastal configuration 
• deforms under its own weight

• subcontinental in scale
• make their own topography
• flow directed by set surface slope of ice sheet

• floating termini
• nourished from up-ice and above
• ablate by basal melt and calving

• local to regional in scale
• make their own topography 
• form on mountaintops 

• constrained by topography 
• ice flow influenced by shape of bedrock 

alpine glacier: 

Valley glacier

• occupies a rock valley
• large valley glaciers may join to form dendritic pattern

alpine glacier:

Cirque glacier

• small ice mass usually occupying a small bedrock depression within a larger valley
• characteristically wide in relation to its length

glacial erosion:

Abrasion

• rocks embedded in glaciers base make linear scratches and grooves in bedrock

glacial erosion:

Quarrying

• glacier breaks off and removes large blocks of rock
• frost wedging is important 

• sliding of basal ice
• debris in basal ice
• ice thickness
• basal water pressure
• relative hardness of debris and bedrock
• efficient removal of fine debris

• lineations gouged into surface below glacier
• indicate direction of ice flow

• concave upstream system of two fractures between which the rock has been removed

chattermarks

[image]

• occur locally within large grooves
• concave downstream or not concave at all
• very small scale feature formed by removal of a single chip of rock

glacial polish

[image]

• smooth striated surfaces abraded by similar hardness and fine load

on downstream side of bedrock leads to development of asymmetric streamlined hillslopes call Roche Moutonee

[image]

firn

• snow that lasts longer than one year
• process by which 2 solids join together to be one solid

drainage basin=

• watershed
• an area on a map outlined by a divide
• all water within basin will drain down to a stream then flow out of basin

1. erosion
2. transport
3. deposition

• typical in flat lying areas
• channel networks 
• [image]

• strongly reflect underlying geologic structures
• located in long linear valleys  where main drainages flow[image]

• strongly reflect underlying geologic structures
• located in long linear valleys  where main drainages flow

• reflect strong control of stream orientation by joint sets
• common where chemical weathering etches joint patterns[image]

• most commonly found on volcanoes
• [image]

Strahler classification of stream ordering

[image]

• a method of classifying or ordering the hierarchy of natural channels
• stream order correlates well with drainage area, but is also regionally controlled by topography and geology

depositional drainage basin landforms

• alluvial fans 
• fill terraces

• strath terraces
• knickpoints/waterfalls and knickzones"

drainage basin landforms

upstream v downstream

• Upstream: changes in sediment or water supply
• downstream: changes in baselevel

• bed load
• suspend load
• dissolved load

• sediment rolling, bouncing and creeping along the river bed
• 5-20% of the total load of a stream
• bed load may move short distances by saltation (short, intermittent jumps)

• sediment that is fine enough to remain in suspension in stream (size depends on velocity and turbulence)
• tributaries can have different sediment loads

• input, transport, storage, and export of sediment from a geomorphic system (hill slope, basin, stream reach, mountain range)

• compare conditions across basins
• estimate response to management actions
• evaluate significance of climatic, tectonic, or historic land use changes
• understand river response to dams, mining, volcanic eruptions, road building, logging, fire

• abandoned floodplains
• relatively flat remnant of former river position
• alluvial terraces
• bedrock terraces

• tectonic uplift
• change in base level downstream
• change in climate modifying system's discharge

strath (bedrock)terrace

[image]

• define erosional surfaces that can be buried under thin alluvial deposits
• typical form due to incision in response to uplift

• a location in a river where there is a sharp change in channel slope, such as a waterfall or lake, resulting from differential erosion above & below knickpoint
• [image]

knickpoints

[image]

fluvial processes

driving forces

fluvial processes

resisting forces

• faster at middle and surface
• [image]

• fixed channel boundaries
• high transport capacity
• low storage
• input is roughly equal to output

• channels floored by bedrock and lacking an alluvial bed cover
• indicative of transport capacity well in excess of sediment supply

alluvial rivers

[image]

• erodible channel boundaries (banks and bed)
• transport capacity <or= sediment supply
• storage can be quite high
• input>or=output

• straight
• meandering
• braided/anasomosing

straight channels

[image]

• rare
• form where streams are confined by topography or follow geologic structures
• generally mountain streams

meandering channels

[image]

• loops or meanders form as stream erodes its banks
• cutbacks and point bars

• erosion takes place here in a meandering channel
• the outside loop of the meander

• deposition takes place here in a meandering channel
• on the inside loop of the meander

• change their channel course gradually
• create floodplanes wider than the channel
  • very fertile soil
  • subjected to seasonal flooding
• most common in fine grained stream sediments and have gentle gradients

helical flow through meanders

[image]

• surface flow on outside of meander bend is forced into the bank and thus down, causing scour and excavating a pool
• flow returns along bottom of meander bend, causing net deposition and creation of a point bar deposit

sinuosity:

big meanders

[image]

• low gradient
• fine substrates

sinuosity:

small meanders

[image]

• high gradient
• coarse substrates

• many converging & diverging streams separate by gravel or sand bars
• clog themselves with sediment, so channel always shifts
• generally in streams near mountain fronts

• high sediment load
• constantly changing coarse
• floodplain completely occupied by channels
• many small islands called mid-channel bars
• usually coarse san and gravel deposits

• the discharge varies both daily an seasonally
• the glacier supplies the stream with large quantities of sediment

meandering v braided

Meandering favored by:

• low slope (<2%)
• low sediment load
• cohesive banks

meandering v braided

Braiding favored by:

• higher slope
• high sediment load
• high discharge variability
• erodible (non cohesive) banks

• the flat land immediately surrounding a stream channel and submerged at times of high flow

how do floodplains form

• deposition of overbook suspended sediment
• deposition of bedload as the channel migrates across its valley

• boundary between channel and floodplain
• broad low ridge of alluvium built along side of a channel by debris laden floodwater

river management 

Hard Engineering

• civil engineers
• many dramatic failures
  • bridge collapses
  • habitat loss and local extinctions

river managment

Soft Engineering

• working with rather than against natural processes
• geomorphologists have greater role

• small headwater channels at the tops of the channel network where sediment transport is dominated by hill slope processes
• [image]

the steepest of mountain channels characterized by tumbling flow around individual boulders; disorganized streamed structure

[image]

step pool channels

[image]

plane-bed channels 

[image]

pool riffle channels

[image]

• most common mountain river morphology
• characterized by alternating sequence of pools and bars

bedrock channels

[image]

• bedrock channels with little sediment can occur anywhere in a river network where transport capacity>> sediment supply

1. isostatically, with a thick buoyant root
2. flexural

• compression
• extension
• shear/lateral