GEOGRAPHY FINAL Flashcards
Detachment
Refers to the detachment of rock particles from a cohesive mass in a bedrock channel
2 ways of detachment
Quarrying and abrasion
Quarrying
Rock is shattered by the shock waves created by the implosion of small, airless bubbles. These vacuum bubbles form in very fast moving water
Abrasion
Grinding down of rock by the impact of sediment particles (like sand pappering)
Detachment is most common where?
Bedrock streams or river channels
Bank carving
Collapsing banks into river to deposit sediment
Second part of erosion: entrainment
Picking up or loose sediment from channel bed by the flow of streak water
Buoyancy
Define me later
Horizontal drag
Water flows left to right
Turbulence
Water curdles as it flows
3 parts to entrainment
Buoyancy
Horizontal drag
Turbulence
3 parts to transport in fluvial erosion
Bed load
Suspended load
Dissolved / solution load
Bedload
Sediment moves down bed (bottom) of stream
Two types of bed load
Saltation
Traction
Saltation
Bounce around, skip down stream
Traction
Roll on bed of stream
Suspended load
Rather than being on bottom, sediment is suspended
Dissolved / solution load
Minerals dissolved in water
Friction due to _____ lake velocity _____ at stream bed
Vegetation
Lower
Hjulstrom curve
Shows how fine sediment can be transported over a much large range of velocities than coarser particles
Different sizes and types of sediment are in _____ with different flow conditions
Equalibrium
Sediment is sorted during transport, with _____ sediment remaining up stream and ____ sediment travelling further down
Coarser
Finer
Deposition (aggradation)
Since deposition or aggradation by rivers and streams is dependant in flow velocity, the deposition
COME BACK TO ME LATR
Thalweg
The line of greatest velocity and depth in a stream or river when viewed from above
3 aspects to river shape
Channel crossing sections
Channel planimetric
Channel longitudinal shape
Channel cross sectional shape
The most effective shape is a parabolic curve, although in reality they have a trapezoidal shape
Channel plaimetric shape
Most river/ streams exhibit sinuosity
4 theories why rivers meander
Coriolis force (bad) Initial wiggling of the thalweg in a straight channel; results in bank erosion and altering
Dissipation or excess or free energy
Stochastic theory
Random geological obstacles cause river channels to be directed in different directions
With distance down stream, 2 things occur
Sediment becomes finer
Discharge increases
Discharge increases
Energy gets greater, work gets smaller
Work =
Transporting sediment load
Energy =
Flowing water
By _____ and using excess energy, the river is attempting to attain ____ between energy and work
Meandering
Equilibrium
Anabranching river
Has multiple channels that can be widely separated from each other and run long distances before rejoining main channel
Braided stream / river
More or less on channel that spilts by gravel bars
Characteristics of braided streams
Easily erode channel
High sediment load
Constant shifting of channels due to deposition
Steeper channel gradient composed to meandering river
Large and frequent fluctuations in discharge (trying to attain equilibrium)
Channel longitudinal shape
The gradient of a stream / river along its length from headwaters to mouth (known as longitudinal profile)
Gradient stream
Where energy and work are in balence
Convex long profiles can develop where the rivers work energy relation changes
(low energy, high work)
Irregularities in the long profile can be produced by
River flowing over more resistant bedrock
Legacy of Pleistocene glacial erosion
Change in sea level
Tech tonic uplift
Base level
Lowest elevation to which a stream / river can erode down to ultimate base level (aka ocean)
Knickpoint
Lowering base level (sudden drop in stream)
Antecedent stream
Posse very deep gorges along their stream
Littoral process
The sea coast or littoral zone can be viewed as an open system for energy and matter
High and low tide
Low tide: ebb tides
High tide: Flood tides
Energy in costal geomorphology
Waves and currents
Matter in costal geomorphology
Sediment, water
What creates most work in littoral zone
Waves
Wave size depends not only on wind speed and duration but also on _____
Fetch
Fetch
Distance in which wind blows
Wave patterns of the world are linked to
Global climate and patterns of water
2 types of ocean waves
1) tsunamis
2) storm surges
Tsunami
Caused from techtonics
Large wave
Storm surges
Created by hurricanes
Potential energy
From wave particles positioned above the wave trough
Kinetic energy
From waves circular motion
When waves approach the beach
Friction slows down, wavelengths decrease, wave height increases, velocity decreases
Swash
Water going onto the beach
Shingle beach
Rocks not sand
At littoral zone, potential energy from waves is converted to ______ ______ as the wave breaks
Kinetic energy
Kinetic energy is what causes geomorpholic work
Waves approach beaches at _____ angles
Oblique (doesn’t equal 90°)
Beachdrift
Produced in surf zone by combined effect of swash and backwash from individual waves
Longshore drift
Produced by longshore currents which is created by the refraction of waves arriving at the shoreline at oblique angles
Groynes
Concrete or rock structure that intersepts the sediment for the beach (makes beach grow)
Jetties
Built for a canal, interrupts sediment transport
Breakwater
Horizontal to coast
Block waves so that cant approach land
Hard
Made by humans, engineered
Soft
Modifying sediment
Ships dropping deposit
Rip current
Special current where waves approach at 90°
Rip feeders
Transport you into rip currents
Geomorphic process in littoral zone
Erosional coastlines
depositional coastlines
Erosional coastlines
Found on coastlines with significant vertical relief, often tectonically active and where energy is high
Depositional coastlines
Low relief, trailing edge of techtonic plate, sediment available from many sources in addition to erosion
Is the littoral zone depositional or erosional
It can be classified as one
Seasonal variation accounts for geomorphic work
Erosional landforms
Sea cliffs, sea arch, sea stack, wave cut platform, landslides
DEFINE THESE
Depositional landforms
Barrier spit, baymouth bar, lagoon, tombolo, shingle beach, barrier beaches
Biological process and features of coasts
Coral reefs
Mangrove swamps
Salt marshes
Coral reefs
The rocks of coral reefs are polyps
Polyps live symbiotically with algae and CaC03
Polyps
Skeletons of tiny marine animals
Specific conditions for coral
Clear, sediment free water
Water temps between 19-29
Max depth of 55 meters
Salinity of 27-40%
Eustatic sea level rise
Melting of glaciers raising water levels
Isostatic sea level rise
Techtonic subsidence. Rising of land or lowering of land
If island is sinking,coral will
Keep its growth to match the sinking
5 types of reefs
Fringing (surrounding coral rock)
Barrier (Enclosed by lagoons)
Almost atoll
Atoll (Circular ring shaped reefs)
Maketea
Coral reefs are on a decline due to
Pollution
Damaging marine organisms and disease
Sedimentation
Warming of oceans
Acidification of ocean waters
Coral bleaching
Temps over 30° causes coral to die
2 types of sea level changes occur on time scales from century to millennia
Eustatic sea level change
Isostatic sea level change
2 reasons for eustatic sea level change
Changes in water temp
Changes in extent of terrestrial glacial cover
Isostatic sea level change cause
Uplift or subsidence of land surfaces due to techtonic forces
Unloading of rock by erosion
Glacial growth and shrinkage
Isostatic rebound
Island lifts, sea level drops
Techtonic Forces two points
Submerged coastlines
Emergent coastlines
Submerged coastlines
Rising sea level frowns or submerges a coastline and its erosional and depositional landforms
Emergent coastlines
Where lowered sea level exposes former sea floor; erosional or depositional landforms are raised above new sea level
Glacial and periglacial geomorphology
The work of glaciers and ground Ice
Glacier types (2 types)
Alpine glaciers
Continental ice sheets
Ice apron
Ice stuck to mountain
Cirque glacier
Wide/ round
Valley glaciers
Occur in valleys, length > width
Piedmont glacier
Pancake batter spreading out
Icefields
Level area with ice
Ice caps
Covers a large area, completely burring the landscape
Ice sheets
Largest glaciers possible; Greenland and arctic
GMB
Glacier mass balence
_____ determines glaciers to carry out massive amounts of ______
GMD
Work
Temporally (GMB)
Where mass balence year is divided into a winter balence and a summer balence
Spatially (GMB)
Where the glacier is divided into o an accumulation zone and an ablation zone
The mass balence at the end of each ______ year greatly differes
Balence
Year after year, mass ice builds up In the -“______ zone and is lost from the _____ zone
Accumulation
Ablation
Ablation is
Melting, evaporation, sublimation
Important part of mass gain and loss
Avalanches
Calving
ice breaks from a glacier into water to form an ice berg
What is required in order to transfer mass ice from accumulation zone to the ablation zone
Glacial movement
2 types of glacial movement
Creep or internal deformation
Basal slip
Creep or internal deformation
Ice in glacier deforms
Basal slip
Base of glacier slides on bedrock
Crevass
Brittle ice that breaks when pressure is applied
The glacial geomorphic system
Consist of sub systems that are linked together (see seperate page)
Erosional processes in a glacial system
Glaciers are efficient erosional agents compared to most other types. Glaciers are covered in sediment
Erosional detachment
Actual prising loose of material from a coherent mass, usually bedrock
4 ways of erosional detachment
Periglacial weathering processes
Abrasion
Plucking
Dilation
Periglacial weathering processes
Ground ice. Freeze thaw weathering
Abrasion
Grinding of basal debris against the glacier bed
Plucking
Water at base of glacier, either from pressure-melting, flows into joints in bedrock floor and refreezes
Dilatation
Pressure release creates by erosion and removal of bedrock at glacier base results in fracturing of bedrock, making easier to erode
Glacial erosion entrainment
Picking up broken rock
Glacial erosion entrainment four types
Material transported by gravity, water, or wind into glacial surface
Traction
Regelation
Ploughing and squeezing
Material transported by gravity, water, or wind into glacier surface
Landslides
Mudslides
Traction
Applied by moving ice
Regelation
Freezing of water produced by pressure melting at base of glacier which includes fine sediment in base
Ploughing and squeezing
A glacier terminus advancing down valley pics up sediment as if advances over soft saturated material
Small scale erosional features are found
Both continental and alpine
Large scale landforms
Typically found in alpine glaciation
Striations
Scratches from abrasion
Chattermarks
Holes from plucking
Glacial grooves
Smooth channels covered in bedrock
From abrasion
Rock drumlins
Smooth bump in rock
Roche moutonnee
Gentle side of mountain with a steep side
Cirques
Large bowl on mountain
Tarns
Lakes in cirques
Horns
Top peak of mountains
Glacial troughs
Classic u-shape
Fjords
Glacial troughs filled with water
Potternoster lakes
Series of lakes in chain
Glacial transport (3)
Subglacial
Englacial
Superglacial
Subglacial
Sediment transported under glacier
Englacial
Sediment locked in ice
Superglacial
Sediment on top of glacier
Most glaciofluvial systems are
Besides streams or rivers
Transport in glaviofluvial systems is
Episodic
Moraines
Landforms created by till deposition
Medial moraine
2 lateral moraines merge
Terminal moraines
Deposits as glacier goes back
Terminal and recessional moraines ca occur on _____ scale with ________ sized glaciers
Larger
Continental
How are moraines great water aquifers
The size of the debris is perfect to hold water
Ground moraine (till plain)
Flat featureless plains of sediment
Drumlin
Direction of glacier movement makes a steep and low angled hill
Kettle lake
Blocks of ice flowing from stream getting stuck, covered in sediment, then melting
Hillslope geomorphology
The work of gravity and water
Hill slope
All land with a gradient steep enough to affect both natural processes and human activities
Why hill slopes
Theoretical
And practical
Theoretical interest
Outputs from slip systems typically become inputs in other geomorphic systems
Practical interest
Much of human activities take place on slopes and populated mountain region slopes must be put to work
Slopes affect agriculture, roads safety
The ____ the slopes, the greater potential for _____
Steeper
Erosion
Hillslopes as a system
Inputs: precipitation, sunlight
Outputs: evaporation
Transfers: run offs
Fundemental of hillslope geomorphology, 2 broad types of movement
Waterborne
Mass movement
Water borne (4)
Rainsplash
Sheetwash
Rilling
Gullying
Rainsplash
Splash distance is greater downstream
Sheet wash
Water washing over slopes in thin sheets
Rilling
Tiny channels or water
Personal waterslides
Gullying
Large transport of water
Mass movement
Driven by gravity and aided by water
Gravity induced stress
The driving force
Is needed to create mass movements
Angle of slope and weight of material
Mathematical equation
F a W x sin u
F=stress
W= weight of slope material
U= slope angle
Resting force
Force that wants to hold material to surface
Resting force is dependant on
Characteristics of the rock
Presence of water
Seismic activity
Characteristics of the rock, sediment, or regolith
Particle shape, size, bonding
Presence of water
Raises the pure water pressure
Pressure exerted by water found in the pore spaces of rock, sediment, or regolith
The angle at which material _____ is typically steep than the material that _______________
Fails
Comes to rest
Angle of initial yield
Angle at which material fails
Angle of repose
Angle material comes to rest
Once slopes are set into motion, ______________ drops sharply even if water isn’t present. Especially in very large mass movements, __________ dramatically lowers frictional resistence, leading to ____________
Frictional resistance
Vibrational energy
Much longer runouts
Types of mass movements
There are many types of mass movements, operating over many time scales
Very slow mass movements
(Soil creep)
Rapid mass movements
Mudflows, flowslides, rockfalls
Mass movements classified on mechanisms of motion
Falls
Slides
Slumps
Flows
Falls
Rock falling, very little or no water, small scale
Slides
Translational slide: material slides parallel to slope
Little water
Slow to fast speeds
Slumps
Hill slide roared backwards as it move little water
Typically small
Flows
Require water
Mudflows, debris flow,
Magnitude frequency spectrum
Small events occur often, large events occur rarely
Special type of flow in periglacial regions containing ground ice or permafrost is:
Solifluction
Active layer
Flows during the warm season due to melt water and rain are unable to penetrate frozen ground
Creep
Extremely slow down slope movement of the surface layer of soil
Reasons for creeps
Repeated expanding and contraction of soil particles
Freezing and thawing
Wetting and drying
Temperature variations
Grazing livestock and burrowing animals
Terracettes
Produced by soil creep over many years
Rock creep
Surface layers of layered and shattered rock
Desert geomorphology
The work of wind and water
Aeolian geomorphology
Processes common in desert and coastal environments
What processes shape deserts
Fluvial geomorphic
Climate feedbacks
amplify or reduce climate trends, either warming or cooling
paleoclimatology
Study of natural climatic variability
proxy methods
information about past environments that represent changes in climate
Mangrove swamps
Trees, shrugs, and plants in intertidal areas
Salt marshes
form in estuaries and behind barrier beaches and splits
surface creep
Particles in wind that roll on ground as it is too heavy to be lifted
Aolian deflation
Wind lifting and removing partciles from ground
Aolian Abrasion
Grinding and shaping of rock due to “Sandblasting”
Ventrifacts
Rocks that are polished from wind
loess
Thick blanket of material
