Geomorphology Flashcards
(45 cards)
What can rocks be in? (3)
Horizontal strata (layers)
Inclined strata
Massive igneous
What are the horizontal strata?
Hilly landscapes
Basaltic plateau/lava plateau
Canyon landscape
Karoo landscape
How are hilly landscapes formed?
In HUMID regions
Mass wasting and sheet erosion cause gentle slopes and a hilly landscape forms.
SUITABLE FOR FARMING
Chemical weathering has taken place forming thick grained soil.
E.g. valley of a thousand hills
In ARID regions
Only mechanical weathering, so soil is thin and coarse-grained and the slopes are rugged and steep.
LITTLE FARMING takes place
How are Basaltic plateau/lava plateau formed?
Drakensburg is an e.g. of a landscape where lava poured through long narrow cracks and layers built up to form a plateau.
The strata are horizontal and uniformly resistant.
GOOD for TOURISM, NOT farming
How are canyon landscapes formed?
Horizontal strata of hard and soft layers erode at different rates.
The hard rocks results in steep slopes while less resistant rock forms more gentle slopes.
A plateau formed through tectonic uplift and rejuvenated rivers cut deep steep-sided valleys.
E.g. Grand Canyon, fish river
Uses:
DAMS,
not farming-too dry
Forms a barrier to transport routes
Tourist attraction
Hydro-electric
How are Karoo landscapes formed?
Valleys widen through backwashing and scarp retreat.
The plateau is protected by a resistant hard layer.
Rivers erode weaknesses vertically to form canyons.
Scarp retreat or backwasting is lateral erosion where rocks of differing resistance maintain their angles. This results in mesas and buttes forming. The hard cap rock forms a flat, protective layer.
Once this layer is removed a conical hill forms.
When does a homoclinal terrain develop?
If the strata of alternating resistance to erosion have been uplifted and tilted then a homoclinal terrain develops.
The alternating strata DIP by the SAME DEGREE and in the SAME DIRECTION.
Describe homoclinal ridges and hogsbacks and cuestas.
A group of slopes is referred to homoclinal ridges but the STEEPLY tilted strata form HOGSBACKS while the GENTLY tilted strata are called CUESTAS.
…..
How are basins and domes formed?
When layers bend they form anticlines and synclines.
When these become eroded they can result in basins and domes forming.
Uses of basins and domes:
Hard layers form less fertile soil
Slopes used for forestry
Cuesta plains agriculture
Cuestas can trap water that is underground, and oil and gas
What are massive igneous rocks?
Rocks with no layers, usually igneous intrusions like batholiths, laccoliths and lapaliths.
What happens when magma cools?
It forms joints and cracks.
Along these, erosion takes place.
What is exfoliation?
When the outer layer peels away due to extreme heating and cooling.
When does a Granite dome form?
When a batholith becomes exposed.
Batholith
Largest
Granite
No apparent base
Laccolith
Mushroom shaped
Pushes areas of strata up
Lopolith
Saucer shaped (inverted mushroom)
Layers cannot support weight
Dyke
Wall like vertical intrusion
Sill
Horizontal intrusion and spreads between layers
Pipe
Chimney shaped
What is a tor?
A pile of unconsolidated core stones-often granite.
What’s the most popular theory for tor formation?
While the rock was still below earths surface, chemical weathering took place along joints.
When the rock became exposed eventually, the weathered material would be eroded away leaving the core stones behind.
If joints widely spaced, core stones would be large.
Concave
Cave in
Convex
Rounded
