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River Erosion And Weathering - Coggle Diagram
River Erosion And Weathering
Weathering
Biological Weathering/organic weathering
Seed falls into the crack of the rock. Over time the seed grows into a plant and roots develop. Soon the roots grow and the rock cracks
Chemical Weathering
chemical weathering describes the process of chemicals in rainwater making changes to minerals in the rock. E.g. statue of liberty
Freeze-thaw weathering/frost shattering
Water falls in the crack of a rock. It freezes and expands 9%. this expanding continues until the rock breaks into two and fall down the slope as scree
Exfoliation/Onion skin weathering
Heat causes the outer layer of the rock to expand. AT night, it becomes cold and hence it contracts. this process being repeated multiple times causes the layers of the rock to peel of like an onion
Erosion
Erosion- Wearing away of land and removing the loosened material is called erosion.
Transportation
sediments carried far away from the weathered/eroded rock
Deposition
depositing sediments far away from the parent rock
Upper course
Features
Waterfalls
River flows over
hard rock overlying soft rocks.
Soft rock erodes faster than hard rock. Water descends vertically and forms a plunge pool.
Formation
After a plunge pool is formed, the hard rock on top lies supported by soft rocks
beneath.
This part is called as overhang.
The overhang collapses due to gravity as water undercuts the soft rock.
This causes the waterfall to retreat (go back).
formation of rapids
Ridges of hard rock amongst the soft rock forms rapids
Rivers flow over alternate bands of hard and soft rock. It leaps over obstructions formed by hard rocks. Called as rapids. Number of rapids together called cascade.
V-shaped valleys
River flows over
soft
rock. Valley sides get eroded and break apart. Now that a steep valley is formed, the sides get weathered an d there is a slope transport. Gets a V-shape. BORDERED BY INTERLOCKING SPURS
Canyons
Large gorges are called canyons
Gorges
River flows over
hard
rock. Vertical erosion>lateral erosion. Hence, the lnd keeps being eroded deeply and narrowly. iT BECOMES A GORGE.
Landforms created…
Chief function of the river is erosion.
It breaks lots of large rock fragments and carries them away
The water has a lot of energy.
River flows over steep hills or mountains.
Used for rough grazing (sheep farming) Tourism, dams
Middle Course
Features
River flows over plains.
Slope of land becomes gentler.
River carries a lot of sediments called
‘load’, ‘alluvium’, or ‘silt’.
Chief function of a river is
transportation and deposition.
Vertical erosion = Lateral erosion.
Joined by tributaries.
Landforms formed…
River cliffs
Meanders
Water bends around obstacles. Force is greater on outer bend. Erosion.Inner bank is slower-deposition. River cliff is on the outer bend. Many bends= meanders
Ox-bow lakes
Continuous side-cutting of rivers causes two meanders to meet (due to erosion), forming a loop. The bow shaped lake is cut off, (deposition). called an ox bow lake
Natural levees
When big flood plain deposits near river causes natural embankment.
Flood plains
Depth of river valley reduces due to deposition of sediments. Water spills on bank during floods or increase. Alluvial deposits remain. Called flood plain.
Used for fields for crops and animals. villages and communication lines can be found alongside it
LOWER COURSE
Landforms formed…
Deltas
Course of river obstructed by its own deposits near mouth. Mounds of deposits form at mouth called delta. The triangular region around the mouth is called a delta.
Distributaries (land form?)
Water distributes into smaller channels called distributaries.
River flows over almost flat land. Chief function of a river is deposition. Vertical erosion almost zero, < Lateral erosion
Used for intensive farming, industry, towns, cities and ports, built on the flood plain
Difference Between the two
one is bc of rocks against rock other is bc of weather
Types and Etc.
Types
Attrition
When rocks hot onto each other making them smaller, rounder, smoother
Corrosion
chemicals in the water dissolve the sediments in the river
Hydraulic action
the force of the flowing water, forces water and air into cracks in the river bed and makes it larger
Abrasion
Flowing water throws the rocks against the river bed and creates cracks
Alluvial deposit
Clay, sand, gravel, organic matter
Rivers- erosion because of flow and rocks in the flow
Ice- the glacier carries stones and boulders frozen onto the icea. act like sandpaper
Sea- waves shape coastlines
Wind- Wind blast/storms can cause erosion
Terms
Estuary- Tidal point where sea meets river tide
drainage basin- where all the water converges at one point
watershed- smaller term for drainage basin
