Factors Affecting River Velocity and Erosion

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Questions and Answers

What is the process of sediment transportation in a river where materials bounce on the surface or floor of the river?

Saltation

What is the term for the dragging and rolling of the river load along the river bed?

Traction

What is the shape of an oxbow lake?

Horse-shoe shape

What is the characteristic of the bank of an oxbow lake?

Shallow convex bank and deep concave bank Signup and view all the answers

What is the condition necessary for the formation of a delta?

The absence of strong ocean current Signup and view all the answers

What is the characteristic of a bird foot delta?

Consists of fine materials called silts and has several distributaries like a bird foot Signup and view all the answers

What type of delta is formed when there is partial submergence in coastal waters?

Estuarine delta Signup and view all the answers

What is the term for the expansion of a river flood plain into the sea?

Seaward expansion Signup and view all the answers

What type of landform is formed by the coalescing of several alluvial fans at the foot of a linear mountain range?

Bajada Signup and view all the answers

What is the term for a temporary inland drainage basin with a shallow lake of fluctuating volume encircled by a mud sheet?

Playa or Salina Signup and view all the answers

What is the characteristic of the slope of a Bajada?

Less than 70 degrees Signup and view all the answers

What type of landform is formed by river deposition in desert areas?

Bajada Signup and view all the answers

What is the term for a dry lake bed that is sometimes filled with water?

Playa or Salina Signup and view all the answers

What is the characteristic of the surface of a Bajada?

Smooth Signup and view all the answers

What type of landform is often found at the bottom of a basin or depression?

Playa or Salina Signup and view all the answers

What type of feature is formed by the coalescing of alluvial fans?

Bajada Signup and view all the answers

What is the primary agent of erosion in a river?

The load or materials carried by a river Signup and view all the answers

What process of river transportation involves the carriage of larger particles suspended in the water as it flows?

Suspension Signup and view all the answers

What is the process of erosion where water enters into cracks and cavities, causing them to enlarge?

Hydraulic action Signup and view all the answers

What is the term for the formation of a fan-shaped alluvial plain as a result of deposition by a river?

Delta Signup and view all the answers

What is the term for the wearing down of the loads as they collide with the valley and one another?

Attrition Signup and view all the answers

What type of delta consists of both coarse and fine sediments and has an inverted cone shape?

Arcuate Delta Signup and view all the answers

What is the process of river transportation where materials dissolve in water and are carried to the lower course?

Solution Signup and view all the answers

What is the term for the bouncing of materials either on the surface or at the floor of the river?

Saltation Signup and view all the answers

What is the process of erosion that occurs on the concave side of a meander in a river?

Erosion Signup and view all the answers

What is the term for the dragging and rolling of the river load along the river bed?

Traction Signup and view all the answers

What is the feature of the lower course of a river where erosion occurs on the concave side and deposition on the convex bank?

Ox-bow lake Signup and view all the answers

What is the characteristic of a river delta that occurs in swampy areas?

Occurs in swampy areas Signup and view all the answers

What is the characteristic of an oxbow lake in terms of its bank shape?

Shallow convex bank and deep concave bank Signup and view all the answers

What is the condition necessary for the formation of a delta, in terms of ocean currents?

The absence of strong ocean current Signup and view all the answers

What is the alternative name for an oxbow lake?

Bayous/Cut-offs Signup and view all the answers

What is the term for the bouncing of materials either on the surface or at the floor of the river?

Saltation Signup and view all the answers

What is the process that occurs when a river's speed and energy reduce, allowing deposition to take place?

Deposition Signup and view all the answers

What is the characteristic slope of a Bajada?

Less than 70 Signup and view all the answers

What is the term for a temporary inland drainage basin with a shallow lake of fluctuating volume?

Playa or Salina Signup and view all the answers

What is the result of river deposition in a linear mountain range?

Bajada Signup and view all the answers

What is the primary factor that contributes to the formation of a Bajada?

Reduction of river speed and energy Signup and view all the answers

In which type of environment are Playas or Salinas typically found?

Desert and semi-arid areas Signup and view all the answers

What is the characteristic shape of a Bajada?

Broad, gentle undulating slope Signup and view all the answers

What is the process by which rivers pick up sediments and other materials as they flow over a linear mountain range?

Erosion Signup and view all the answers

What is the main cause of aridity in desert areas?

Interior location or continentality Signup and view all the answers

What type of desert plants have longest roots?

Phreatophytes Signup and view all the answers

How are sand bars typically formed?

Through deposition by wind Signup and view all the answers

What is a characteristic of desert landscapes?

High rate of evaporation Signup and view all the answers

What type of desert is characterized by a surface covered with gravels, stones, and pebbles?

Stony desert Signup and view all the answers

Which of the following is NOT a characteristic of deserts?

High vegetation cover Signup and view all the answers

What is the term for a desert that is formed by erosional process of deflation and abrasion?

Rocky desert Signup and view all the answers

Which desert is considered the driest in the world?

Atacama Signup and view all the answers

What is the main characteristic of a desert?

Barren land with little precipitation and poor living conditions Signup and view all the answers

What type of plants are found in deserts that have no leaves?

Xerophytes Signup and view all the answers

What is the process that forms a sand bar?

Wave deposition in shallow sandy waters Signup and view all the answers

What is the characteristic of the Sahara Desert?

Hot desert in Africa Signup and view all the answers

What is the term for a place having little or no rainfall?

Aridity Signup and view all the answers

What is the characteristic of the Atacama Desert?

The driest desert in the world Signup and view all the answers

What is the name of the desert plants with the longest roots?

Phreatophytes Signup and view all the answers

What is the unique feature of Antarctica?

The largest cold desert in the world Signup and view all the answers

What is the primary factor that contributes to aridity in desert areas?

Interior location or continentality Signup and view all the answers

What is the term for desert plants with longest roots?

Phreatophytes Signup and view all the answers

How are sand bars formed?

Through wave deposition in shallow sandy waters Signup and view all the answers

What is a characteristic of deserts?

Absence of vegetation cover Signup and view all the answers

What type of desert landscape is characterized by an undulating plain of sand and sand dunes?

Sandy or Erg Signup and view all the answers

What is the term for the desert that is the driest or rainless in the world?

Atacama Signup and view all the answers

Which of the following deserts is NOT a hot desert?

Antarctica Signup and view all the answers

What is the primary cause of aridity in desert areas?

Interior location or continentality Signup and view all the answers

Which of the following is a characteristic of Stony or Reg deserts?

Presence of gravels, stones, boulders, and pebbles Signup and view all the answers

Which of the following is NOT a characteristic of desert landscapes?

Abundance of vegetation cover Signup and view all the answers

What type of desert landscape is formed by wind deposition?

Sandy or Erg Signup and view all the answers

Which of the following is a function of wind in desert areas?

All of the above Signup and view all the answers

What is the process of wind erosion that involves the lifting and blowing away of loose sand and pebbles?

Deflation Signup and view all the answers

What type of desert landscape is formed by the erosional process of deflation and abrasion?

Rocky or Hamada Signup and view all the answers

Which of the following is an example of a Badland or Mountain Desert?

Ahaggar in Algeria Signup and view all the answers

What is the term for a desert surface covered with gravels, stones, boulders, and pebbles?

Stony or Reg Signup and view all the answers

What is the main cause of aridity in desert areas?

High evaporation rate Signup and view all the answers

Which type of desert plants have the longest roots?

Phreatophytes Signup and view all the answers

How are sand bars typically formed?

Through the deposition of sediment by rivers Signup and view all the answers

What is a characteristic of desert landscapes?

Low relief and flat plains Signup and view all the answers

What type of desert is characterized by a surface covered with gravels, stones, and pebbles?

Hamada desert Signup and view all the answers

Which of the following is NOT a characteristic of deserts?

High vegetation density Signup and view all the answers

What is the term for a desert that is formed by erosional processes of deflation and abrasion?

Reg desert Signup and view all the answers

Which type of landform is formed by the coalescing of several alluvial fans?

Bajada Signup and view all the answers

Study Notes

Factors Affecting the Velocity of a River

The volume of water released affects the velocity of a river
The slope of the river valley affects the velocity of a river
The shape of the river valley affects the velocity of a river
The amount and size of materials affect the velocity of a river

River Erosion

The load or materials carried by a river are the main agents of erosion
There are four processes of erosion:
- Hydraulic action: water enters into cracks and cavities, causing them to enlarge
- Corrasion: wearing of the sides and floor of the river valley by sand, pebbles, silts, and boulders
- Attrition: wearing down of the loads as they collide with the valley and one another
- Solution: chemical action of water on materials

Processes of River Transportation

There are four processes of river transportation:
- Solution: materials dissolve in water and are carried to the lower course
- Suspension: carriage of larger particles suspended in the water as it flows
- Saltation: bouncing of materials either on the surface or at the floor of the river
- Traction: dragging and rolling of the river load along the river bed

Ox-Bow Lake

Formed in the lower course of a river where there are pronounced meanders
Formed through erosion on the concave side and deposition on the convex bank
Characteristics:
- Feature of the lower course of a river
- Occurs in marshy areas
- Has a horse-shoe shape
- Has a shallow convex bank
- Has a deep concave bank
- Also called Bayous/Cut-offs

Delta

A fan-shaped alluvial plain formed as a result of deposition by a river
Mode of formation:
- Deposition of sediments
- Absence of strong ocean current
- Presence of sediments at the estuary
Favourable conditions for formation:
- Active vertical and lateral erosion
- Tideless coast or sheltered coast
- Shallow sea adjoining the delta
- No large lakes in the river course
- No strong current at right angle to the river
Characteristics:
- Found at the lower course
- Occurs in swampy areas
- Has seaward expansion of river flood plain
- Composed of alluvium
- Has distributaries
- Has many shapes
Types of delta:
- Arcuate delta
- Bird foot delta
- Estuarine delta

Bajada

A broad, gentle, sloping sediment bordering the foot of a mountain range
Formed by river deposition in desert areas
Characteristics:
- Found in desert areas
- Features of river deposition
- Fairly gentle undulating slope
- Smooth surfaces
- The slope is less than 70

Playa or Salina

A temporary inland drainage basin with a shallow lake of fluctuating volume encircled by a mud sheet
A temporary salt lake found in arid and semi-arid areas
Characteristics:
- Found in desert areas
- Features of desert river deposition
- Contain temporary salt lake
- Usually found at the bottom of the basin or depression
- Examples: Playas in Algeria and Salinas of Lake Magadi of Kenya

Desert Landforms

A desert is a barren land that receives little precipitation with poor living conditions to support plant and animal lives.
Most desert or arid areas in the world lie between 150 and 300 north and south of the equator.
The world's largest cold desert is Antarctica, and the world's largest hot desert is Sahara.
The driest or rainless desert in the world is Atacama.
The only continent with no desert is Europe.

Causes of Aridity

Factors that influence aridity in desert areas include:
- Interior location or continentality
- Cold ocean current
- Rain shadow effects or leeward location

Characteristics of Deserts

Low precipitation or rainfall
High temperature
Absence of vegetation cover
High rate of evaporation
High rate of physical or mechanical weathering
Wind action is dominant
Presence of cold current
Internal drainage
Presence of landforms

Types of Desert Landscapes

1. Sandy or Erg: an undulating plain of desert with large amounts of sand and sand dunes, produced by wind deposition. Example: Coastal sandy desert of Western Sahara.
1. Stony or Reg: a desert surface covered with gravels, stones, boulders, and pebbles, produced by daily temperature change or exfoliation process of weathering. Example: Kalahari desert in Africa and Hamada el Homra in Libya.
1. Rocky or Hamada: a desert surface covered with large stretches of bare rocks, produced by erosional process of deflation and abrasion.
1. Badland or Mountain Desert: a desert landscape developed in arid regions of sudden rainstorm. Examples: Ahaggar in Algeria and Badlands in Dakota (USA).

Functions of Wind in Desert Areas

Wind performs three functions in desert areas: erosion, transportation, and deposition.

Actions or Processes of Wind Erosion in Desert Areas

Deflation: the lifting and blowing away of loose sand and pebbles by wind.
Other processes include cliffs, coastal cave, arch, stack, stump, geo, and gloup formation.

Features of Coastal Deposition

Beaches: made up of sand and gravels, formed when sand and gravels are loosened from the land. They are depositional features.
Sand Spits: ridges of sand and gravels formed by long shore drift across inlet.
Marine Dunes or Dune Belts: the movement of large amounts of coastal sand by onshore winds with large force.
Sand Bar: formed by wave deposition in shallow sandy waters, a built-up of sand which is at times covered by water at high tide and exposed at low tide.

Desert Landforms

1. Inselbergs or Bornhardts: isolated residual hills with rounded tops and steep sides rising abruptly from the surrounding plains in desert regions, formed from semi-arid and arid regions by the action of running water or wind erosion.
Characteristics of Inselbergs:
- Found in semi-arid and arid areas
- Features of rainfall and running water
- Height may rise up to about 300 meters high
- Most inselbergs are made up of granite gneiss
- Examples: Shai and Krobo Hills in Ghana and Brangberh Hills in Namib Desert

Mesas and Buttes

1. Mesas or Buttes: flat table-like and steep-sided landmass with resistant horizontal top layer underlain by layers of soft rocks, formed by the actions of extreme temperature, running water, rainfall, and wind erosion on alternate bands of hard and soft rocks.
Characteristics of Mesas and Buttes:
- Found in semi-arid and arid areas
- Products of running water, rainfall, or wind action
- Flat-like land masses
- Isolated flat-topped hills
- Examples are found in Sahara and Kalahari Deserts.

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Quiz on the factors that affect the velocity of a river and the processes of river erosion including hydraulic action and corrosion.