Geomorphology Flashcards
Strata
Anotehr term for layers of rock
Stratified rock
Rock composed of layers of strata
Bedding plane
Planes separating layers of rock
guillies
Narrow, long areas of erosion on a slope
Plateau
A large, flat high lying landform
Sheet wash
Rainfall flowing over land as a sheet
Lava flow
Lava pours onto surface, cools and solidifies
How does horizontally layered rock form - two ways
1.Sediments deposited on top of each other consolidate + forms rock
2.Large scale lava flow
Landscapes associated with horizontal strata *4
*hilly landscapes
*basaltic plateaus
*canyon landscape
*karoo landscape
Hilly landscapes and basaltic plateaus provide…….. resistance to erosion
Uniform- same speed
Canyon landscapes provide……. resistance to erosion
Alternating
Explain how hilly landscapes are formed
Sedimentary strata with uniform resistance form a steep hilly landscape
Influence of humid areas on hilly landscapes *2
*rounded slopes because of sheet wash
*rainfall removes surface material on slopes
Influences of dry areas on hilly landscapes *
*steep with sharp ridges bc no sheet wash
*hills with narrow guilles form in arid climates
What are hilly landscapes in arid climates called
Badlands
Outburst aka
Successive fissure eruption
What do outbursts cause
Lava to flow on the surface
Explain how basaltic plateaus form *2
*lava flows on the surface bc of outbursts
*a layer of basalt if formed - provides uniform resistance and gives rise
Has uniform resistance
What does vertical erosion in basaltic plateaus cause
Deep, narrow gorges
What is tectonic uplifts due to
Crustal forces
What erosion takes place in canyons
Vertical
How does a plateau form a canyon
Tectonic uplifts
Influence of humid climate on canyons
*water erodes slopes - rounded and gentle
Influence of dry areas on canyons
*sharps ridges and steep uneven badlands - lack of rainfall
Dolerite still
Horizontal layer of igneous rock formed along a bedding plane
Where do Karoo landscapes form from
Canyons
How do Karoo landscapes form
Canyon floor gets wider, plateau surface gets smaller
Why do plateaus hold original height
Resistant cap rock
Order that plateau erodes in *4 - Karoo landscape
Mesa > butte > pointed butte > conical hills
Mesa
Flat topped mountain with greater width than height
Butte
Flat topped mountain with greater height than width
Pointed butte
Narrow hill with sharp peak
Conical hill
Small pointed hill
Conical hill
Small pointed hill
Scarp retreat
Erosion causing loss of width but not height
As plateus narrow, canyon floors become…
Wide
How are hilly landscapes utilised
*in humid climates slopes are steep + chemical erosion creates fertile soil - farming
Why can’t farming be done in high altitudes of basaltic plateaus *2
*cold temperatures
*rugged slopes bc vertical erosion
Why can farming be done in lower altitudes of basaltic plateaus *2
*not as cold
*basalt weathering creates fertile soil
Chemical weathering
Decomposition of rock due to chemical processes
Water, carbon dioxide, oxygen
Mechanical weathering
Decomposition of rock due to extremes in temperature
Utilisation of Canyon
Tourist attractions
Utilisation of Karoo *2
*Maybe farming, but precipitation is an issue
*Attractions
Inclined strata formation
Sedimentary layer is uplifted and tilted
Landscapes associated with inclined strata *
*homoclinical landcape
*cuestas and hogbacks
Homoclinal landscape *2
Landscape formed of inclined strata* tilted by the same degree of dip in the same direction*
Undercutting
Erosion at the base of a slope with the collapse of overhang
Homoclinal shifting
Movement of Homoclinal ridge towards dip slope
Homoclinal shifting
Movement of Homoclinal ridge towards dip slope
Mass wasting
Movement of eroded material downhill due to gravity
Scarp slope
Steep slope of Homoclinal ridge
Dip slope
Gentler slope of Homoclinal ridge
Why is erosion less on dip slope
Resistant rock strata
What is erosion on scarp slope due to
Sheet wash and mass wasting
How does scarp retreat take place
undertaking takes place and collapses the scarp slope
Homoclinal displacement
Erosion of ridge:
Moves in direction of dip slope, not getting lower
How are cuestas, Homoclinal ridges and hogsback differentiated *1+3
Angle of resistant strata
Cuesta - 10-25*
Homoclinal ridge - 25 - 45*
Hogsback 45*
Cuesta
Ridge with gentle dip slop and scarp slope
Hogsback
Ridge with steep dip slope and scarp slope
What are Cuesta basins and domes a result of
Folding
Cuesta dome *2
*Circular landform as a result of erosion of anticline
*Folded strata raised into a dome
Cuesta basin *2
*Circular landform as a result of erosion of syncline
*Folded strata bent into a basin
Folding
Rocks are bent when pressed from both sides
Characteristics of Cuesta dome *3
*strata pushed into shape
*scarp slope points inwards
*dip slope points outwards
Characteristics of Cuesta basin *3
*strata folded into shape
*scarp slope points outwards
*dipslope points inwards
Magma extrusion *2
Magma forces itself through weak spots in the surface*
Comes to land as lava and cools and solidifies*
Magma intrusion *2
Magma flows as reaches the crust*
Moves existing rock to the side forming new rock*
Utilisation of dip slope of Cuesta
Course + infertile slope - forestry
Utilisation of scarp slope of Cuesta
Too steep, can’t be used
Utilisation of Homoclinal ridges
Doesn’t have barriers between them - transport routes
Utilisation of poort between Homoclinal ridges
Good for dam wall
Utilisation of Cuesta basin
Yields artisian water
Utilisation of Cuesta dome
Yields oil and gas
Poort
Gap between two mountains created by river erosion
How are intrusions formed
Magma flows through crust, cools and solidifies
Batholith characteristics *1+3
*large magma dome shaped intrusion
*magma cools slowly to form large rock mass
*usually granite
*no bedding planes
Laccolith definition and characteristics *1+4
*small mushroom shaped magma intrusion
*connected by pipe to intrusion source
*magma intruding strata causes them to dome
*dolerite is formed if magma cooled closer to the surface
*granite is formed if magma cooled deeper in the crust
Lopolith definition and characteristics *1+2
*pan shaped intrusion found deeper in crust
*bend downwards
*usually granite
Dyke definition and characteristics *1+1
*vertical dolerite sheets
*form when magma intrudes into vertical cracks
Sill definition and characteristics *1+2
*horizontal dolerite layer
*fluid magma intruded between bedding planes
*stratified rock rather than massive
What do massive rocks have rather than bedding planes
Joints and cracks
Contractual joint
Joint formed when magma cooled
Off-loading joint
Joint formed when the weight of overlying material was removed
Granite dome
Landform caused by erosion of overlying strata to expose a batholith
Exfoliation
Peeling of rock layers due to expansion and contraction
Tor
Exposed granite blocks made from core stones -
Mass of loose core stones surrounded by weathered debris
Why can’t tors form if joints are very close
Granite is mass weathered underground
Explain the theory of slope decline by W.M Davis *2
*Steep slopes are created by rivers eroding vertically into uplifted landmass
*Slopes are less steep to the point where peneplain is formed
Peneplain
Nearly flat plain formed from erosion of slopes
Down wasting
Erosion of land mass where it flattens over time
Pediplain
Nearly flat plane formed as canyons widen
Back wasting
Erosion of land mass when it gets narrower
Scarp/parallel retreat
Erosion of scarp slope - loss of ground but not height
Explain scarp retreatment theory *3
*landscape started as uniform slope with equal weathering
*scree accumulates at base
*scree replaces gentler slope - doesn’t get lower
🏔️Mass movement
Downward movement of weathered material as a result of gravity
Factors that can influence mass movement *min 4 max 7
*slope gradient
*rock structure
*vegetation
*soil
*climate
*people
*earthquakes
How does vegetation prevent erosion and downward movement *2
*roots bound soil
*vegetation provides resistance
Three categories for mass movement
Flow
Slide
Fall
Types of flow mass movement *4
*soil creep
*soilfluction
*earthflow
*mudflow
🏔️Soil creep definition and characteristics *1+4
*slow continuous movement of soil down a slope
*less than 1cm per year
*expansion (soil and water) then contraction after soil dries
*forms small steps - teracettes
*indicated by bent landforms - accumulation of soil against them
🏔️Solifluction definition and characteristics *1+2
*top soil is saturated, slides off frozen ground beneath
*terrace-like landforms, destroyed OG soil stratification
*5cm - 1m per year
🏔️Earthflow definition and characteristics *1+2
*clay soil particles are saturated with water - move down a gentle slope
*5cm - 15km per year
*sediments deposited in river systems, damage roads
🏔️Mudflow definition and characteristics *1+3
*streams of mud flows down a steep slope in definite channels
*1km per hour
*running water collects clay and ash - moved rapidly
*damages property
Slide mass movement types *2
Landslides
Slumps
🏔️Landslides and slumps definition *1+2
*sudden movement after a large mass of land breaks and plunged down a slope
*50km per hour
*impacts are more severe - property damage, death, loss of crops
Fall mass movement type
Rockfalls
🏔️Rockfall definition and characteristics *1+3
*rock fragments break off parent mass bc of weathering
collected as bottom as scree
*most rapid form - 100km p.h
slopes 40 or steeper
Just know impact is the worst
Impact of mass movement on people *4
*Death and injury
*Damage to infrastructure
*Property damage
*Damage to agricultural land
Why do people clear vegetation *5
*settlement
*transport routes
*dumping
*recreation
*quarrying
Quarrying
Removing material from bottom or side of hill
🏔️What needs to be implemented to minimise mass movement effects *5
*research on geology, ecology and rainfall in that area
*vegetation must be maintained
*drainage measures
*landslide areas must be restricted
*risk assessments must be conducted
🏔️Factors that increase the risk of mass movement *5
*saturated pore water
*layered rock
*downslope
*extensive development- little vegetation
*steep slope angle
