Share this:


  1. 2. CLIMATE
Variation of climate cause differences in the rate and type of weathering. The main climatic controls are of temperature and humidity. However the role of climate in weathering is extremely varied region to regions depending in temperature and rainfall patterns. Hence type of climate determines the rate and type of weathering.
      1. Equatorial regions – These are characterized by high temperature and rainfall throughout the year. Chemical composition of rocks is very active in these latitudes due to high temperature and high rainfalls totals.
      1. Tropical (Savannah) regions – These are characterized by the seasonal variation of rainfall and temperature i.e. there is dry and wet seasons. Due to the presence of both seasons, both chemical weathering and mechanical weathering takes place. Chemical weathering during wet seasons and mechanical weathering during dry seasons.
      1. Hot Deserts – These are characterized by large diurnal temperature range i.e. day temperatures are extremely high while night temperature fall more rapidly. There is low amount of rainfall and
        excessive evaporation. Both mechanical and chemical weathering take place mechanical by the process of exfoliation and (frost action) and chemical by salt crystallization due to excessive evaporation.
      1. Mountain regions – These are characterized by high humidity and low temperature. Hence, frost action is active in tropical regions where there is an existence of mountains with height above 430m like Elgon and Ruwenzori, frost action is also common.
  1. 3. RELIEF (Slopes).
At steep slopes the rate of physical weathering will be fast but chemical weathering is retarded because H2O moves (no penetration of water).
On lowland, physical weathering will be slow because weathering is protected by weathered materials and chemical weathering will be faster because water is there and will influence weathering.
Under relief there is aspect -is the position of a place in relation to sun rays. North facing slopes do not face sunlight hence it is less developed and weathering takes place slowly but in the south facing slope, weathering takes place fast and well developed soil and good vegetation.
    • In the tropical regions t
      here is no aspects
    • In mountainous regions frost action takes place actively.
  1. 4. ROCK AGE.
Old rocks are more susceptible to weathering as they had enough time been much subjected to different weather forces compared to young rocks. It is thus, the rate of weathering is higher to old rocks compared to young rocks.
  1. 5. BIOTIC ACTIVITIES
Biotic activities contribute a lot to weathering in varied ways and include;
        • Penetration of plant roots causes physical destruction of rocks.
        • Some plants and animals secrets acid from their bodies leading to decomposition of rocks.
        • Burrowing of animals also cause mechanical weathering
        • When the living organisms in the soil respire, give out carbon dioxide gas. The gas dissolves in water to form carbonic acid, which cause decomposition of rocks.
        • In other way round, thick vegetation cover, such as tropical forests acts as a protection against physical weathering and also helps to slow down the removal of weathered materials.
        • Human activities, poor methods of agriculture expose the bed rock to weathering.
Study Questions
  1. 1. Discuss exhaustively the role of water in the weathering process.
  2. 2. Where and for what reasons mechanical weathering is a dominant process.
  3. 3. “Mechanical weathering and chemical weathering processes are interdependent and complementary” Discuss.
  4. Weathering is not influenced by force of gravity but mass movement is influenced by force of gravity.justify
II. MASS WASTING (Mass Movement)
Is the down slope movement of weathered materials under the influence of gravity. In this movement, there is no transporting agent.H2O is involved as a lubricant and not a transporting agent. Water helps to reduce friction of particles within weathered materials. And also water adds to bulkiness, this will facilitate the process of mass wasting.
Types of mass wasting
Two types according to the speed of movement
a) Slow mass movement
    1. Soil creep
    2. Solifluction
    3. Talus creep
    4. Mudflow
b) Rapid movement
        1. Slump
        2. Rock slide or sometimes both slump and rock slide are called “land slide”.
        3. Rock fall
    1. SOIL CREEP
Is a steady downward movement of soil on all sloping land. Rain water lubricates soil particles and enables them to slide over each other.
Ø Is the slowest and imperceptible movement of weathered material, mainly fine soil down a gentle slope.
Ø Soil creep can be manifested through mounds of soil behind the walls, tilting and cracking of walls, bending of trees, fences and telegraph poles as well as cracking of the road.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
In equatorial regions creep is often disguised by dense vegetation cover.
    1. SOLIFLUCTION
Movement of weathered materials under frost areas. It is limited to mountain and cold climate areas where thawing causes a saturated surface layer to creep as a mass over underlying frozen ground. (Saturated soil, gravels and weathered rock).
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
    1. TALUS CREEP
This is also a very slow movement of angular waste rock of all sizes (talus or scree) down a slope. It is common on the sides of the mountains, hills and scraps. It takes place where free- thaw action is common especially in the highlands and high latitude regions.
Large talus sheets move mass especially in mountains where freeze – thaw is frequent. Talus moving down a valley in a long stream is a rock glacier.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
    1. MUD FLOW.
Movement of large volumes of unconsolidated materials which are super-saturated with water, the materials flow as semi-liquid mud (as slurry) with boulders and gravel embedded in mud.
Large volumes of unconsolidated material, super-saturated after heavy rain, become plastic and flow common in acid and semi arid region.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
    1. SLUMP.
Massive rocks overlying weak rocks saturated by heavy rain common on over steepened slopes. Large masses of rock and debris.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
    1. ROCK SLIDE.
Is sliding movement of the slab of rock down the steep slope, no rotation is involved. It can be triggered off by earth quake or human activities like mining or cultivation.
Surface rocks sliding over a slip surface formed by bedding or fault planes dipping sharply down slope.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
    1. ROCK FALL
Is a falling movement of individual rock blocks with boulders along a precipitous (steep) slope of a mountain or along road cuttings or cliffs.
Precipitous slopes in mountains where well jointed rocks may be loosened by freeze – thaw.
Rocks accumulate as a talus slope along valley sides.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
FACTORS WHICH AFFECT THE NATURE AND SPEED OF MASS WASTING
  1. a). The degree of saturation and nature of weathered material
The more saturated the weathered material is the faster the rate of movement. Because there is more friction between particles.
Depth of weathered materials, weakly bedded and steep dipping the faster the rate of movement.
  1. b). Gradient.
Steeper the slope, the faster the rate of movement and vice versa.
  1. c). Climate.
Amount of rainfall, nature of rainfall , the annual and day temperature ranges. Heavy rain or alternative freezing and thawing encourage movement.
Heating and cooling.
  1. d). Vegetation cover.
Absence of vegetation cover to hold the material
s will increase the speed of mass wasting.
  1. e). Human activities.
Mining, overgrazing and keeping of animals are among the ways in which man has affected the stability of the surface and facilitates the rate of move.
  1. f). Earth movement
Especially earth quake which can disturb the rocks and encourage mass wasting. Effect of mass wasting
  1. 1. Loss of life.
Example, for those who build their settlement down the hills, rock fall many occur for mountain climbers the avalanche may fall.
  1. 2. Destruction of property.
Example, those farms which are on the foot of the hill or on a slope may be destructed by mass wasting (soil creep, land slide, rock fall) buildings, roads, railway lines, river all these become blocked by mass wasting and land slide.
  1. 3. Attract tourism.
The resulting feature after mass wasting has occurred can arrange the rocks in such a way that is attractive to the human eye. Also human beings like to see the effects of a disaster first hand.
  1. 4. Land degradation.
Removal of fertile soil from the land. It leaves scars which is less value than the before land.
  1. 5. Formation of fertile soil on the foot of the hill where weathered materials have accumulated.
  1. 6. Can dam a river to form temporary lakes. But the weathered materials are loose hence water will remove the weathered materials and the river will continue to flow.
PRECAUTIONS:
ü – Afforestation and reforestation on slope lands. This will help to the stability of weathered material, will reduce rate of move.
ü – Control human activities. Especially poor methods of agriculture (contour cultivation will stabilize the farm). ü – Avoid establishing settlement in areas which are prone to mass wasting.
ü – Making of terraces across of slopes.

Study questions.
Carefully distinguish mass wasting from
weathering.
Mass wasting weathering
    1. Influenced by gravity 1. Disintegration and decomposition of rock.
    2. Movement of weathered materials 2. Types include physical and chemical
    3. Types include slow mass movement and rapid. 3.Generally restricted to material breakdown in place
    4. Processes range considerably in rate 4. Is a surface phenomenon
EROSION
Is the detachment and removal of weathered materials from the surface of the earth surface by agents of erosion.
OR Is the process of breaking up and wearing away of exposed rocks by moving water,wind and moving ice.
Agent of erosion;- There are four agents of erosion
i. Running water ii. Wind iii. Glaciers (moving ice) iv. Waves and tidal currents.
EROSION BY RUNNING WATER
What is running water?
· Is any water which falls on the ground and flows down slope under the influence of gravity.
When water in running on the surface performs three functions ,that is Erosion,Transportation and Deposition.
What happens when water fall on the surface of the earth?
    • Percolation – When H20 is absorbed in the ground.
    • Evaporation-Rain
    • Surface run off- Is most effective agent of erosion over the earth surface
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
Surface run off cause’s soil erosion
Types of erosion
        1. Sheet erosion.
Uniformly removal of upper soil without well defined channels.
Removal over a large area of a top layer of soil and other fine materials by a thin sheet of H20 flowing over a fairly smooth surface.
        1. Rills erosion
Removal of upper soil from surface with well defined channels called rills. The impact of rills is more effective than sheet erosion.
        1. Gully erosion.
If rills are not checked they will collide and come larger and to form big channels called gullies. Removal of soil by these gullies is what is called gully erosion. Gullies are also grooves or depression of v-shaped.
        1. Splash erosion.
Is the rain drop impact on the surface. Particles are displaced by rain drops (loose dry materials). Impact (result).
i. Formation of small channels which will leads to formation of badlands. ( smooth land – bad land
which is less useful)
        1. Bad land
        2. Gullies
        3. Rills.
EROSION RIVER, WIND, GLACIER AND WAVES
RIVER
Mass of water flowing in a natural channel over the earth surface from the high land to low land under the influence of gravity.
TYPES OF RIVER
1. Perennial River:-These are rivers which flow throughout the year .The source of these rivers is the region with a abundant and well distributed rainfall throughout the year. E.g Nile River(Africa),The Congo river(Africa) and the Amazon in South America.
2.Intermittent Rivers:-These are the rivers which flow only during the wet season in the regions which receive seasonal rainfall.
3. Ephemeral Rivers:-These are the rivers which appear during the rainy season in the areas which experience very little rainfall especially the desert.They tend to disappear immediately after the rain season has stopped.
River vs stream
– River and stream are used interchangeably.(used the same way)
Terminologies associated with rivers.
  1. Rivers head. (River source).
Is a point where the river or stream begins. It makes its first appearance on the surface / it is the highest point on a river system.
Possible river sources
      1. Lakes – R. Nile in Lake Victoria.
      2. Mountains with plenty rainfall e.g. Rockies and Appalachian ( Mississippi river ) R. Ganges, Indus (Himalayas)
      3. Springs.i.e. Thames River in England.
      4. Melting ice i.e. Rhine river in France.
  1. River mouth.
Is a point where the river ends. The lowest point / base level of the river.
Possible river mouth
    1. Oceans – River Rufiji – Indian ocean.
– River Nile – Mediterranean Sea.
    1. Lakes – River Kagera – Lake Victoria -River Malagarasy – Lake Tanganyika.
    2. Swamps
    3. Others rivers – (Blue Nile meets with White Nile)
  1. Water shed/ catchment area/River basin.
Is a collecting ground of single river system. Where a river collects its water.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
Tributary:Is a branch of river pouring its water into a main river.
Distributary: Is a branch of a river which collect its water from the main river.This is more prominent in the lower stage as is associated to delta formation.
  1. Divide:
Is a highland separating two adjacent river systems.
  1. River system:
The main river and its tributaries ( distributes)
  1. River valley:
Lowland between two hills of drainage basin where at the bottom the river flows. (At the lowest point a river flows)
  1. River bed:
Is the actual part of the river which is covered by water (flowing water).
  1. River load:
Is the materials carried by running water.
WORK OF RIVERS
Works of a river includes three processes.
        1. Erosion
        2. Transport
        3. Deposition
1. RIVER EROSION.
Is the progressive removal of materials from the floor and side of the river / progressive removal of materials from the river bed.
Vertical erosion. – Deepens the river channel.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
Section across a river channel.
Lateral erosion – Widens the stream.
Head ward erosion – Takes place on the upper course which lengthens the stream.
The process of river erosion is accomplished through four interaction process. i. Hydraulic action
Refers to the force of moving water which is able to remove loose materials such as gravel, sand and silt and which is able to weaken solid rock by surging into cracks in the rock [from the sides and the floor of the river]
  1. Corrosion
Is solvent action of water (solution). Process of removing soluble materials by moving water e.g. Limestone or Calcium carbonate.
  1. Corrasion
Wearing away of the river bed by the load of the river.

  1. Attrition
Impact of the load of the river upon itself, this takes place because the rock fragment which made up the load are in constant collision with each other.
2. RIVER TRANSPORTATION
Movement of materials from one place to another by the river.
Mechanisms:
i. Suspension.
A lite material whose specific gravity is less than one is carried above the floor as suspended load.
    1. Saltation
Those particles which are large are transported in series of hops (bounces from one point to another, touches the floor at given interval).
    1. Traction.
Transportation of the load by dragging on the floor. Continuously touches the floor.

    1. Solution.
If river passes through soluble rocks, the materials dissolve in water and become soluble and cannot be seen.
– Transportation of the load depends on the energy and power of the river.
Power – ability to do work but power depends on energy to be able to perform a certain work.
Energy of the river Depends on
  1. Volume
  2. Velocity.
Volume + Velocity = Discharge.
i.The volume of the river is how large the river is (size) ii.The velocity – How fast the river flows.
  • Large volume will have more energy than a slow flowing river also the larger the velocity the greater the energy.
  • Volume and velocity of a river is what is called river discharge ( is the number of cubic meters per second passing through a particular section river ) (m3/sec)
  • This discharge is measured by a current meter which is placed in the river which has a dialogue (current meter) which automatically records the energy of the river at any point.
-The velocity of a river varies from one place to another across the channel, Due to
i.The middle part of the river has maximum velocity.(maximum energy ) because the friction is less.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
ii.Velocity of the river varies with gradient. A river with steep gradient has high energy compared to a river.
iii.The shape of the channel also has great influence on the energy of the river.
  • A shallow and wide channel has less energy because friction is less compared to a wide channel.
A.Channel B losses more energy through friction than channel A but channel C has the greatest available energy due to the channel.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
  1. Due to the large size of the channel.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
  1. It is important to note the difference between the river channel and the river valley.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
THE HEIGHT OF A RIVER ABOVE THE BASE LEVEL OF THE RIVER.
Base level of the river.
Is the lowest level of a river can erode. When a river ends on the lakes or oceans is the base the r
iver.
-The height of a river above its base level gives it what called potential energy (P.E). (Energy due to position.)
-When water flows, potential energy is converted into kinetic energy which does the work of the river.
A river uses its potential energy to.
      1. To overcome friction in the river bed.
      2. To erode
      3. To transport the materials /load. The rate of erosion along the river channel depends on
    1. Volume of the river.
The larger the volume of the river the higher the rate of erosion.
    1. Velocity.
The higher the velocity the greater the rate of erosion (greater the rate of distraction)
  1. The type of rocks over which a river flows:
A river can flow over soft rocks, erosion will be more and rate of distraction will be high but if flows over hard rocks, erosion will be low.
  1. Type of cutting tools (type of load the river carries).
To do corrosion if it takes large load the rate of erosion will be high compared to a river which carries small load the rate of erosion will be low.
RIVER COMPETENCE AND RIVER CAPACITY
RIVER COMPETENCE
Is the ability of a river to carry large load in term of size individual particles.
  • At particular places and particular velocity.
  • A river competence is high where a river is narrow because the energy is higher compared to large slow moving water because energy is slow.
River capacity
Is the ability of a river to carry a large load in terms of the volume.
  • A large slow moving river has high capacity but low competence and vice versa.
  • A fast flowing moving river has high competence but low capacity.
  • The ultimate goals of a river are to being the land above the sea level to its base level. But this cannot be achieved because there is adjustment.
3. RIVER DEPOSITION.
What is river deposition?
Lay down /dropping of the load transported by a river.
Why deposition.
  • It deposits its load when the energy of the river is insufficient to carry the load further.
When does this occur?
    1. When the volume of the river decreases.
When the does the volume of the river decrease and force deposition?. When it enters arid and semiarid regions (dry land /hot desert) because evaporation increases and percolation increases (more reduction of water in the channel as it Wets the ground) or when it enters regions of porous rock and limestone regions or in the dry seasons (droughts) because no addition of water from rainfall.
    1. When its velocity decreases (speed).
When does the speed decrease? When the gradient falls velocity decreases and energy decreases
    1. When a river enters a lake or swamps the speed decrease because it meets with another force.
    2. When a river enter ocean/sea. Because it encounters some waves and tidal currents (encounter forces).
The stronger the encounter force.
    1. When the river channel widens. Friction increase where by the energy decrease and leads to deposition.
DEVELOPMENT OF THE RIVER VALLEY
Long profile and cross profile of a river.
Long profile of a river:
Is the whole length of a river from its source to its mouths.
Cross profile of a river:
Is the width across the river from bank to bank.
  • River erosion leads to development of varies features along the valley as erodes from sources to mouth. These features are studies acquired to stages of the river.
THREE STAGES OF A RIVER
Upper / torrential / youthful stage
Middle / mature
Lower / old /plain
LONG PROFILE OF A RIVER FROM ITS SOURCE TO ITS MOUTH
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
CROSS SECTIONS
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
CHARACTERISTIC FEATURE OF YOUTHFUL STAGE /UPPER
    1. Deep, narrow valley (v-shape) because vertical erosion is dominant. Therefore it deepens the valley.
    2. Valley has step gradient –The speed of the river is very high
    3. Presence of pot-hole
    4. Presence of interlocking spurs
    5. Presence of water fall and rapids.
POT –HOLES
–These are circular depression on the river bed.
-H20 swirl when it passing on that depression
  • Formed where the rock is softer than the surrounding rocks due to uneven river bed. Erosion of fast flowing water swirls in the depression deepening and widening it.
-A. pothole can be much wider and deeper depression
Form at the base of a water fall and form a plunge pools.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
Presence of inter locking spurs.
What are spurs?-is a high land projecting into a lower land. A river at the upper course cannot overcome obstacle it will swirl around the obstacles.
-Spurs alternating on either side of the river interlock/overlap
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
Waterfalls -A sharp breaks on the river channel where the water falls from higher level to a lower level.
Causes of water falls
  1. Difference in rock hardness
  2. Uplift of land (tectonic forces ) (earth movement)
  3. Glaciated valleys.
  4. At a cliff.
  5. River rejuvenation.
Waterfalls formed by difference in rock hardness
  1. Inclination of the hard rock. Rock layer is horizontal
  2. Rock layer dips up stream
  3. Rock layer is vertical. (vertical dyke
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
Example of water falls
  1. Gersoppa falls India
  2. Victoria falls Zambia
  3. Niagara falls between lake Erie and Ontario
  4. Living stone falls Zaire river
Rapid -: Is a part of stream where there is sudden increase of speed/velocity of water in a stream/river.
Causes of Rapids/when do they occur
    1. When the hard rock dips gently down stream
Rapid.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
    1. During recession of water fall (Retreats)
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
Gorges – An elongated steep sided trough/hollow (deep) always occur where waterfall retreats. (Waterfall migrate up to river)
Canyons – Formed by H2O recession or uplift of the land (areas of up lifting) e.g. the grand canyon.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
CHARACTERISTIC FEATURE OF MIDDLE/MATURE STAGE
    1. Valley has open V – shaped valley ->because lateral erosion is dominant.
    2. The speed of the river has decreased because slope decreased volume/ has increased because more tributaries join it and this in turn means that the river load increases.
    3. River beds are pronounce because of maximum erosion on the concave side and even undercutting of the outside of the curve, the concave banks stand up as river cliff because there little erosion or even deposition on the inside of the bend ,the convex bend slope gentle as clip – off slopes (smoothed ends of spurs ). The river starts to meander and river plains are formed.
    4. BluffsAs spurs are removed, their remains form a line of bluff on each side of the valley floor.
    5. Deposition start to take place on a fully mature valley
CHARACTERISTIC FEATURE OF OLD/PLAIN STAGE
1-The gradient is very low and a river develops meander aimlessly along a wide flood plain. Its energy has decreased hence cannot overcome obstacles it then create banks
2-The main work of the river is deposition and deposition it forms some features on the river bed e.g.Braided stream,Ox-bow lakes,natural leaves ,delta etc.
Braided stream -Due to deposition on the river bed will build some mould and causes the river to split into several channels which rejoin and split again.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
Formation of oxbow lakes -: Forms when meander is so acute that only a narrow neck of land separate the two ends of the meander.
      1. Neck of the land separate 2 concave banks where erosion is active.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
      1. The neck is ultimately out through; this may be accelerated/often during river flooding.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
      1. Deposition seals the cute –off which become an ox –bow deposition take place along the two ends of the cut off and eventually seal off to form Ox-bow Lake.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
Production of the natural levees:-Formed through successive flooding near the river because as the water flood out of the main channel its speed is immediately checked by friction with the banks and the heavier sediments are drooped first.
-Ridge/embankment on the sides of the river formed caused by river deposition especially after flooding. -Deferred tributary –Is a tributary which flow parallel to the main river which tries to enter it but the main river is high above the flood plain.
-Deferred junction –Is the point at which the tributary enters the main river.
Example; Ya-zoo streams flows for 200km without managing to join the river Mississippi.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
Formation of delta-
What is delta: Is a large, flat low lying plain on the river mouth where deposition takes place.
è Deposition continues to takes place on the river mouth which causes the river to divide into various channels called Distributaries
Types of delta
There are many types of delta. But the main types are;
i. Arcuate delta. ii. Estuarine delta. iii. Bird foot delta
i. Arcuate delta
– It is made up of many distributaries.
-The load is composed of coarse and fine materials.
-It is triangular in shape.
Examples Nile, Ganges, Niger, Indus and Hwan Ho.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
ii. Birds foot (digital)Delta -Has few and long distributaries
-Triangular in shape -Fine and very fine sediments.
-This will occur where the river energy is very low.
Examples Mississippi, Omo River in Ethiopia. And also the wave energy is low:-deposition takes place comfortably.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
iii> Estuarine delta
  • Has a shape of estuary (sub merged river mouth) deposition takes place on the sub merged part of the river (estuary). It is also triangular shaped.
It has no distributaries.
Examples Elbe delta (Germany), Vistula delta (Poland). EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)
Formation of flood
Formation o floodplains
  • Is a broad gently sloping surface of alluvium deposits immediately after the river channel.
– Produced by the deposition of alluvial and other materials on the floor of the river valley through which river meanders
Stages in the formation of delta.
The stages in the formation of a delta in an ocean or sea are:-
  1. STAGE 1 : Deposition divides the river mouth into several distributaries. Spits and bars arise and lagoons are formed. Depositions on the banks of the distributaries produce levees which extend into the river or sea.
  1. STAGE 2: Some lagoons have already begun to fill with sediments which cause further division of distributaries into smaller distributaries. The delta has a more solid appearance though it is still very swampy and is usually well covered with water loving shrubs and threes.
  1. STAGE 3: further in filling of lagoons plus the growth of a complete covering of vegetation results in the older parts of the delta coming to stand a above water level and to form dry land.
Conditions necessary for the formation of delta
    1. The river must have a large load and this will happen if there is active erosion in the upper erosion of its valley.
    2. The velocity of the river must be sufficient low to allow deposition
    3. The rate of deposition must be higher than the rate of removal by tidal currents.
    4. There shouldn‟t be any obstacles in the upper levels of the long profile.
EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)




Share this:

EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)

subscriber

4 Comments

  • EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)

    Emmy Tabz, May 10, 2024 @ 8:39 am Reply

    Educative

  • EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)

    Baraka Thobias, April 13, 2024 @ 9:01 pm Reply

    Ipo saw

  • EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)

    Matovu Joselle, March 29, 2024 @ 10:32 pm Reply

    Wow these notes are too supportive for a student

  • EcoleBooks | GEOGRAPHY As LEVEL(FORM FIVE) NOTES THE DYNAMIC-EARTH AND CONSEQUENCE (2)

    Amos Pastory, March 14, 2023 @ 6:42 am Reply

    Make this service so that we can use it for free and not until data alf put it and translate into swahili

Leave a Reply

Your email address will not be published. Required fields are marked *

Accept Our Privacy Terms.*