24 July 2020

Erosion and deposition

Difference between weathering, erosion and deposition.

-          Weathering, erosion and deposition are a set of linked processes that create natural features on the land.

-          Weathering and erosion wear away the Earth’s surface.

-          Deposition builds up Earth’s surface with some of the material produced by weathering and erosion.

Weathering

-          It is the breaking down of rocks and soil by the action of the elements of weather eg, water, moving ice, temperature changes and wind.

-          There is very little movement other than loose material falling under the force of gravity.

-          Weathering attacks rocks and soil through the following processes

a)      Frost shattering/freeze-thaw action

b)      Exfoliation

c)      Carbonation

d)      Oxidation

e)      Biological weathering

Erosion

-          It always involves movement of material whereas weathering happens in one place.

-          Three agents of erosion include, water, wind and ice.

Deposition

-          Weathering and erosion produce rock particles, sand and soil

-          This material is deposited in places on the land.

-          Some of the features made by deposition are sand dunes, scree slopes, beaches, and river deltas.

Rivers- Features of erosion and deposition (along a river course)

Key Concepts

a)      Load- all the loose material moved by a river, which is also deposited as a delta

b)      Silt- very fine material transported in a river

c)      Tributaries- smaller rivers that flow into larger rivers

d)      Scree- small rocks and loose stones that collect on a slope

e)      River delta- many branches of a river, formed by silting, where the river meets the sea.

-          River erosions happens when a river flows over the land.

-          A river carries different kinds of weathered material; this is why rivers are often a muddy colour

-            The material transported in a river is called river’s load, this is mostly sand, silt and stones.

-          It is usually the sand that wears away the land.

-          Stones and sand bounce along, wearing away the river bed and the sides of the river.

-          The size of the pieces in the load gets smaller on the river’s journey from its source to the sea.

-          Some of the world’s rivers actually flow into the sea, most rivers flow into other rivers as tributaries.

Features of erosion and deposition on a river’s upper curse

-          Rivers flow faster on steep land.

-           Faster flowing rivers can transport a heavier and larger load.

-          The movement of large boulders and rocks along the river bed causes downward erosion, this produces a deep valley with steep sides.

-          Waterfalls, rapids, gorges and canyons are features of the upper course of a river.

Features of erosion and deposition in the middle and lowers course of a river

-          Sideways erosion and sideways movement of river is noticeable in the middle and lower courses.

-          River valleys are wider there.

-          There is more deposition of the river’s load

-          Rivers often have large bends called ‘meanders’

-          Features in the middle and lower course include; meanders, ox-bow lakes, deltas, levees and floodplains.

Activity 1

1.      What is the difference between a meander and a delta?

2.      Explain how erosion and deposition cause meanders to change shape in a valley

3.      Describe the role of erosion ad deposition in the formation of an ox-bow lake. Use diagrams to make your explanation clear.

4.      Explain the similarities and differences between;

a)      Levees and deltas

Use the following in your answer; flooding, load, deposition, and energy.

NB; ANSWER YOUR ACTIVITIES IN YOUR GEOGRAPHY EXERCISE BOOK UNLESS ITS A FORMAL TASK FOR SUBMISSION!!

Some more notes and diagrams will be uploaded as attachement!! Take Care!!