EFFECTS OF MASS MOVEMENTS

EFFECTS OF MASS WASTING.
Mass wasting results into number of effects both to environment and human being. Such effects include the following:

• Formation of scars. It occurs when materials breaks away from hillside. When a slump occurs, they leave behind scars on the land.
• Soil erosion. It is a process where it occurs following formation of scars as a starting point for soil erosion.
• Formation of new landforms. Where mass wasting takes place may results into the formation of various landforms such as barrier lakes.
• Changing of river course sometimes mass wasting may results into the changes of river direction of flows. Example mud flow in the Rif atlas mountains of Morocco pushed the course of river Rhesana 100 metres to the east. 
• Damage to property: where it occurs it causes damages to property. Some mass wasting destroys telephone lines, roads, railway lines, fences, hedges and stone walls.
• Loss of life: some form of mass wasting can result in the loss of life. Example avalanches when it occurs it always claims the life of many people.

THE FRENCH REVOLUTION 1789-1790'S

The French revolution 1789-1790’s
Was one of important historical revolutions the world experienced. It was the revolution waged by middle class people against feudal autocratic regime of King Louis XVI of France in 1789. At the time of revolution France was divided into many classes where by the middle and lower class had many discontent toward the regime in power.
Classes that existed in French at the time of revolution

1. Clergy class: these were the people who run the church .their income where through churches properties.  They also got privilege from the king and his government. They owned land which they used to correct rent from it through renting to peasants. Also they were free from taxation.
2. Nobility Class: these were the king’s administration officers. They were living in Versailles city under feudal administration helping the king to rule the country. These nobility were divided into great nobility (richest one,) the Lasser nobility (second rank of nobility) and last was robe nobility who had acquired the title of nobility basing on their service they offer to the king and the loyal family (they had no wealth).
3. The Bourgeoisie Class:  it was the small class consists of merchants (traders), doctors, industrialists, lawyers and other professional group which together formed the middle class. They had no privilege, not included in the government, taxed high, those who where in army had no chance of promotion to higher ranks.
4. Lower Class (Peasant Class): this was the lower class who owned nothing. They had no land, they were highly taxed, and they had to pay high rent.

Background toThe French revolution 1789-1790’s

• At the time of the revolution French was under the regime of LOUIS XVI who claimed himself to have Devine power.i.e power derived from the God and thus he claimed that he was not answerable to anyone in the state.
• There were no proper laws and thus people were unfairly punished. And sometimes a person can be tried fifty times or even more for the single offence he or she has committed.
• On the side of economy there were economic hardship whole over French and the government was severely indebted due to luxury life of the loyal family and government participation on American war of independence.  On other hand people were highly taxed to meet government expenditures.
• Food shortage was the call of the day due to decline in production as the outcome of bad weather condition which hit the country.

Causes of the French revolution.

1. Heavy taxation. The government imposed different taxes which came to be a burden to the peasants and bourgeoisies class as nobility and clergy class enjoyed tax exemption. Such taxes imposed included;a gabelle tax or salt tax which was imposed to all people aging 8 years old and above , whereby they were forced to buy salt each amounting to 7lb of salt per year.

Peasants also had to pay poll tax to the king, twentieth of his or her income to the king and had also to pay tithe of his produce to the church.Toil tax was also paid for the use of local needs such as path, road, mills etc.
Furthermore there were direct tax imposed on each individual. All of these seem to be the heavy burden to the people and thus they decided to revolt against the regime hence united and wage the revolution.

2. Dictatorship regime of the king: the king ruled French under dictatorship. He assumed himself divine power and thus those who questioned his authority or ways of ruling were imprisoned and sometimes even got killed. The King changes and introduced new taxes whenever he wished and he even dissolved the parliament when challenged or questioned his authority. All these created discontent among the people and hence ought to overthrew the King as the means of getting rid of harsh conditions of the regime.

3. Economic hardship/ bankrupt of the government: the government faced severe economic hardship as the outcome of being bankrupt caused by misuse of government fund due to luxury life of the loyal family. Also American war of independence cost  the government 1,200,000,000 livres. Thus altogether ,war cost and luxurious life made French government to be highly indebted  and thus the government were paying 236 million livres out above 472 million livres income each year as interest on the national debt.

4. Influence of American revolution:  apart from causing financial hardship in French, American war of independence brought ideas of freedom , liberty and equality. The people of America were not fighting against misgovernment or being taxed rather they were fighting only for their self rule. Thus  when French soldiers compared  American situation and that of theirs and peasant at home they found they have more reasons to rebel against their government at home and thus  general Marquis de Lafayette returned home from America six years before revolution to rebate the French people against the regime.

5. Bad advices from the queen Marie Antoinette:  the king was under fatal influence of his wife, Marie Antoinette. Ignorant of the need for reform, unsympathetic to her people’s need and incapable of grasping the political situation, she poisoned Louis mind first against the Turgot and then against Necker and everywhere advised a fatal firmness at precisely the wrong moments. These in turn made majority to hate the king and his regime and thus joined revolutionary movement.

6. Influence of great thinkers and philosophers: example Voltaire who criticized the church and proposed that the property owned by the church should be given to majority peasant.
Jean Jacque Rousseau suggested the need to have democracy and get rid of autocratic regime of the King Louis XVI through his work “du contrat social” he sketches his idea of basis of government arguing that men were born free but subjected to chains of government and thus need to be liberated and left free.

7. Food shortage/ bad climatic condition: there was food shortage everywhere in French. The situation was caused by the bad climatic conditions  of 1788 which ruined the harvest ,raised the cost of  corn to a famine price, and caused wide spread starvation  only to be followed by severe winter of early 1789, when all great rivers  of France were frozen and even the port of Marseilles,In the south was blocked by extreme ice.  The situation led to many people from country sides to gather in Paris hoped for food and shelter led to Paris Mob idles.
8. Role of the church: the Roman Catholic Church also influenced French revolution as it was declared as nation religion where by denied people rights to worship in denomination they wished.  Also the church as one of feudal institution taxed the peasant forcing them to pay rent and tithe. Furthermore the church had its own laws used to tries those who broke the law of the church.

9. Poor and unfair laws and judicial system: there was poor and unfair further more un uniform law all over the country. Sometimes people were imprisoned without a trial or for a single crime a person could be tried several times sometimes up to 50 times for the single crime offence.

Effects of French revolution
1. Decline of the power from feudal monarchy and being replaced by bourgeoisies who took the control of the state.

2. Development of capitalism and spread of industries in French and later the rest of Europe. Poor peasants who were once exploited were turned into working class in newly growing industries.

3. It led to the development and spread of democracy in French and later Europe and the rest of the world where ideas of freedom and equality as well as liberty were practiced.

4. It led to unification of small feudal state into one strong country under Napoleon rule.

5. French revolution led to death and destruction of properties as it involved violence and bloodshed were by king and the queen were caught and hanged.

6. It led to confiscation of church property
Brought about freedom of worship were formally it was declared that Roman Catholic to be national church.

7. Freed people from intensive feudal exploitations such through rent, taxation and tithe on side of church.

Contribution of French revolution to the rise of democracy in the world.

• French revolution brought constitutional government in French which later on adopted by other nations. Constitution insured and guaranteed the rule of law where all people were equal before the law such that no man was above the law as it was during autocratic regime of King Louis XVI.
• It brought election system whereby all people got right to contest, vote, elect and be elected as a leader in different position ones fit. Through this it led to rise of common man into political power such as Napoleon Bonaparte.
• French revolution brought about the declaration of human rights which is one among the important elements of democratic states. Human rights ideas later came to be adopted by other states.
• It brought about parliamentary system of government and consolidated representative system which is adopted all over the world to date.
• The rule of law and the constitution brought about power separation in French and later all over the world where by there were three pillars of the government which were Judiciary, Executive and Legislature each work as an independent entity without being interfered by others.

MASS MOVEMENTS(MASS WASTING)

MASS WASTING:
Mass wasting (also called mass movement), is the process whereby weathered material is moved a relatively short distance downslope under the direct influence of gravity.
 It is a collective term for the downslope transport of surface materials in direct response to gravity.
Mass movements are aided by gravity and no geomorphic agent like running water, glaciers, wind, waves and currents participate in the process of mass movements. That means mass movements do not come under erosion though there is a shift of materials from one place to another.

Gravity is the principal force responsible for mass wasting, but water is often a contributing factor.
Water contributes to weathering,

•  which prepares rock material for mass movement,
• adds weight to porous materials on a slope, 
• decreases the strength of unconsolidated slope material
•  and can increase the slope angle. 

Water is involved in many weathering processes that break and weaken rocks, making them more susceptible to mass movement.
The movement may be gradual or sudden, depending on the gradient of the slope, the weight of the weathered debris and whether there is any lubricating moisture supplied by rain water.

Mass movement is dominant where there are weak unconsolidated materials, thinly bedded rocks, faults, steeply dipping beds, vertical cliffs or steep slopes, abundant precipitation and torrential rains and scarcity of vegetation etc., favors mass movements.

Factors Influencing Mass Wasting:

1. Removal of support from below to materials above through natural or artificial means; where material become loosen due to various natural or cultural factors they are easily subjected to down slope movement as the lack base to hold them. 
2. Increase in gradient and height of slopes; where the slope is steep or vertically like cliff slope mass movement is rapid and where materials are large in size such as rock blocks fast or rapid mass movement takes place. 
3. Overloading through addition of materials naturally or by artificial filling; If additional material accumulates on a debris pile lying on a slope that is near the angle of repose, the newly added material may upset the balance (because the added weight overcomes the friction force that is keeping the pile from sliding) and may cause all or part of the material to slide downward.
4. Overloading due to heavy rainfall, saturation and lubrication of slope materials (Water): water performs for main activities which engineer mass movement. First additional of water acceralate weathering of rocks which provide raw material for mass movement. Second water adds weight of weathered materials on a slope. Also water decreases the strength of unconsolidated slope material, and lastly water increase the slope angle. For these reasons, mass wasting is particularly likely to occur during and after heavy rainfall, snowmelt or subsurface flow.
5. Occurrence of earthquakes, explosions or machinery; earthquakes , explosions during mining activities or war, tend to shaken the land and up sate the balance which in return forcing unconsolidated material to be set in motion down the slope as mass movement.
6. Removal of natural vegetation. Where there is severe removal of vegetation mass movement is likely to occur. Where there is vegetation, plant roots holds material together, on other hand vegetation provides a protective cover. But severe removal of vegetation makes weathered material prone to mass movement.
7. Clay: is another facilitator of mass wasting. Clays readily absorb water; this absorbed water combined with the fine-grained texture of the material, makes clay a very slippery and mobile substance. Any material resting on clay can often be set in motion by rainfall or an earthquake shock, even on very gentle slopes. Indeed, some clay formations are called quick clays because they spontaneously change from a relatively solid mass to a near-liquid condition as the result of a sudden disturbance or shock.
8. Permafrost: In subarctic regions and at high latitudes, mass wasting is often initiated by the uprooting action of frozen groundwater. The presence of thawed, water-saturated ground in summer overlying permanently frozen subsoil (permafrost) also contributes to mass wasting in such regions. Some geomorphologists assert that, in the subarctic, mass wasting is the single most important means of transport of weathered material.

CLASSIFICATION OF MASS WASTING.

Physical geographers classify mass wasting events according to the kinds of Earth materials involved and the ways in which they move. Mass wasting according to the way they move is classified into slow mass movement and rapid mass movement.

 With regard to the earth materials moved there is fine materials such as mudflow, medium materials such as soil creep while large materials includes likes of avalanches and rock fall.

Generally mass movements are categorized into fast and slow mass movement as materials moved being large or medium can be moved fast or slow.

SLOW MASS MOVEMENTS.

Soil creep: is a slow and gradual continuous movement of soil downhill slopes. The movement is gradual to the extent it is not very noticeable especially where the slope is fairly gentle or where the soil is well covered with grass or other vegetation.
 It is common in damp soil where the water acts as lubricants such that individual soil particles move over each other and over underlying rock.
 This movement also occur where there is overgrazing in such a way that continuous trampling of by herds of cattle on the slopes sets up vibrations which loosen soil and cause it to move.  Where there is soil creep it is evidenced by tilts of trees, fences, posts. Soil is also seen to accumulate at the foot of slope or behind obstacles such as walls.

Talus creep, rock creep, rock-glacier creep: the slow migration of particles to successively lower elevations. The movement is similar in occurrence as soil creep and both a collectively referred as creep. The only difference is on type and size of particles moved. Creep is so gradual that it is visually imperceptible; the rate of movement is usually less than a few centimeters per year. Yet creep is the most widespread and persistent form of mass wasting because it affects nearly all slopes where there are weathered materials at the surface.

Solifluction (soil flow); refers to the relatively slow downslope movement of water-saturated soil and/or regolith. Solifluction is most common in high-latitude or high-elevation tundra regions that have permafrost, a subsurface layer of permanently frozen ground.
Above the permafrost layer lies the active layer, which freezes during winter and thaws during summer. During the summer thaw of the centimeters- to meters-thick active layer, the permanently frozen ground beneath it prevents downward percolation of melted soil water.
 As a result, the active layer becomes a heavy, water-saturated soil mass that, even on a gentle incline, sags slowly downslope by the force of gravity until the next surface freeze arrives. Evidence of Solifluction exists in many tundra landscapes. It consists of irregular lobes of soil that produce hummocky terrain or mounds.

RAPID MASS MOVEMENT.

1. Earthflow.it is mostly dominant movement in humid region where by presence of precipitation makes materials on the surface getting saturated with water causing them to flow downhill under the influence of gravity. It is dominant in hillsides and terraces. Occurrence of earth flow results into leaving behind a shallow scar at the place where materials have been removed. Where materials deposits they form bench like terraces.
2. Mudflow: Is faster downslope movement of fine saturated grains of soil, usually moving in a specified channel partly or whole of its movement. They can be moving within gullies or canyon stream channel. They are the outcome of torrential rainfall or snowmelt along the hill especially where there is little or absence of vegetation. The movement is triggered by water saturating the debris causing saturated debris to be set in motion. The movement is also dominant in volcanic slope of recently erupted volcano where volcanic ashes, dusts and other fragments turn into muds and start to move down the slope stream of muds or tongues creating greater impact. This volcanic mudflow is called LAHAR.
3. Land slide or land slip: is the rapid movement of large mass of earth’s and rocks down a hill or mountain side. Where it occurs it is accompanied by little or no flows of water. Rain water from heavy rain act as a lubricant that facilitate movement of materials. The common forms of land slides are slump, debris slide, rock slide, and rock fall.
4. Rock fall is rapid falling down of large blocks of rocks which occur in area of extensive outcrop rocks on steep hill slope or canyon walls. It involves individual rocks or boulders that fall or roll freely from a steep slope or vertical slope like hill. The size of rock fall varies depending on manner in which rocks disintegrate. In glaciated area thawing of ice makes the rocks to lose its compaction with the land hence provide a room for gravity to overcome rock resistance.
5. Debris fall: it is common form of rapid mass wasting occurring on a cliff where by loose materials on top of a cliff or any slope which is almost vertical fall freely to the base of the slope. 
6. Rock slide: is the downward movement of rocks in a sliding manner on a gentle sloping area. In this movement water act as a lubricant.
7. Slump: is a form of landslide which involves the tearing away of rock materials along a concave plane.it occurs in a steep slope where massive sedimentary strata usually sandstone or limestone overlie weak rocks like clay or shale.
8. Avalanche: is the suddenly sliding and falling of a large mass of snow, ice and loose rock materials down a mountain side. The movement is dominant in temperate regions during winter or spring season. Accumulated quantities of ice usually break away and slide over hardened snow surface. During spring the thawing of masses of snow may also result in ice sliding downhill. Sliding materials are roll as they move downhill. 

FACTORS AFFECTING THE RATE AND NATURE OF WEATHERING

FACTORS AFFECTING THE RATE AND NATURE OF WEATHERING
The rate, speed and type of weathering are determined by several factors including the ones listed and explained below:

1. Nature of the rock: basing on nature of the rock consideration is made on the following character and constituent of the rock:

• Mineral composition of the rock: rocks are made up of different minerals sum of which are soluble when reacts with water while others are resistant. Where rocks contain minerals which are less resistant to water weathering particularly chemical weathering become rapid and dominant. Example salt rocks (NaCl) and (KCl) as well as Gypsum. Some rocks containing aluminum and iron when react with oxygen present in water undergoes rapid chemical weathering. Quartz has a very low solubility and thus resistance to chemical weathering hence undergoes slow mechanical weathering.
• Rock joints or rock fractures: where rocks consists of several cracks and joints, weathering both chemical and physical weathering is more likely to occur simply because, the lines of weakness allowing infiltration of water into the rock which creates room for reaction of oxygen, carbon dioxide or hydrogen with rock minerals hence decaying of the rock through oxidation, carbonation or hydrolysis respectively. On other hand rock joints create room for frost action to take place.
• Mineral colour. The colour of the rock is determined by the colour of minerals made up the rock. Mineral colour has an influence in the rate of expansion and contraction of rocks due to temperature change. Light coloured minerals has low degree of heat energy absorption hence less expanded due to temperature influence unlike dark coloured minerals where due to high  rate of heat absorption expands and shrinks rapidly which over time results into the formation of cracks hence disintegration of rocks.

• Exposure of the rock or relief factor: where the rock is exposed to weathering agents such as temperature (sun heat energy) or water weathering both physical and chemical becomes dominant. On a steep slope the rate of removal of weathered material is rapid hence the rocks becomes much exposed to weathering agent particularly heat. Likewise in lowland areas water collects and over time favors chemical weathering to occur such as oxidation in water lodging areas. Where the rock is exposed or unloaded after a long period of being compressed exfoliation may occur.

2. Organisms or biological factor: living organisms both plants and animals can in one way or the other results into weathering of rocks.

• Animals such as burrowing animals exposes rocks to the agents of weathering and also break down soft rocks resulting into disintegration of rocks(weathering of rocks).
• Likewise various human activities such as mining, quarrying and cultivation results into physical weathering of rocks. Also some chemicals introduced by man into the soil or water mix up with water to cause chemical weathering of rocks.
• On other hand plant roots penetrates into rock joints and as they continue to grow in size forces rock joints to expand causing physical weathering of rock. Also plant release humic acid through plant roots and also when some of the plant decompose, this humic acid react with rock minerals causing decaying of rocks.

3.Climate: climate (temperature and humidity) plays a greater role in determining the rate and type weathering.
Chemical weathering is enhanced by a combination of high temperatures and abundant precipitation.
Of these two factors, the moisture is usually more important than temperature in determining type and rate of chemical weathering. Example oxidation is the outcome of reaction of oxygen present in water and iron or aluminum mineral present in water. Hydration, hydrolysis, carbonation also operate under the presence of water.

Thus chemical weathering is much pronounced in hot and humid regions such as in equator and tropical areas where rainfall is abundant.

Most desert regions, because of a general lack of precipitation, mechanical weathering may be more dominant than chemical weathering where temperature acts as dominant factor through alternate heating and cooling.
Also salt crystallization is more pronounced in desert and semi-arid because of capillary action.

There are many variations in the connection between weathering and climate.
 Notice that, the depth of active weathering tends to be relatively shallow in regions of tundra and desert but relatively deep in regions of tropical rainforest.

SIGNIFICANCE OF WEATHERING
1. Weathering processes are responsible for breaking down the rocks into smaller fragments and preparing the way for soils erosion and mass movements.

2. Biomes and biodiversity is basically a result of forests (vegetation) and forests depend upon the depth of weathering mantles.

3. Weathering helps in modifying land forms and creation of new features. That means, weathering aids mass wasting, erosion and reduction of relief and changes in landforms.

4. Weathering of rocks and deposits helps in the enrichment and concentrations of certain valuable ores of iron, manganese, aluminium, copper etc., which are of great importance for the national economy.

5. Weathering is an important process in the formation of regolith and soils.

6. Weathering provides building materials such as stones, gravels for construction of buildings and roads.
7. Some newly modified and formed landforms attract tourism activities.

NOTE:
1. Two general kinds of weathering processes take place: mechanical (physical) and chemical. Mechanical weathering causes rock bodies to break into smaller rock fragments, whereas chemical weathering causes the rock to change chemical composition.
2.Although mechanical weathering and chemical weathering can occur anywhere, most mechanical weathering occurs in cold environments, whereas chemical weathering is more pervasive in warm/humid climates.
3.The three major kinds of mechanical weathering are frost wedging, salt-crystal growth, and exfoliation. Frost wedging involves water that expands and contracts upon freezing and thawing in joints and cracks in rock. Salt-crystal growth occurs when water seeps out of rock in arid environments. Exfoliation happens when rock expands because of unloading and temperature changes.
4. The three major kinds of chemical weathering are hydrolysis, oxidation, and carbonation. Hydrolysis occurs when water interacts with rocks, causing chemical reactions to occur. Oxidation occurs when oxygen combines with metals to form oxides. Carbonation takes place when carbonic acid in precipitation accumulates on rocks and causes them slowly to dissolve.
5. Humans have increased the amount of chemical weathering downwind of industrial cities through the process of acid rain. Most of these acids come in the form of sulfur dioxide and nitrogen oxides derived from coal-burning power plants.

DENUDATION PROCESSES AND RESULTANT LANDFORMS

DENUDATION
The overall effect of the disintegration, wearing away, and removal of rock material is generally referred to as denudation, a term that implies a lowering of continental surfaces.
Denudation is accomplished by the interaction of three types of activities:

 Weathering is the breaking down of rock into smaller components by atmospheric and biotic action agencies.

Mass wasting involves the relatively short-distance downslope movement of broken rock material under the direct influence of gravity.

Erosion consists of the removal, transportation, and eventual deposition of fragmented rock material over wider areas and sometimes to greater distances than is the case in mass wasting.

Weathering
Describes the combined action of all processes that cause rock to disintegrate physically and decompose chemically because of exposure near the Earth’s surface. There are two types of weathering which is:
Physical weathering where rocks are fractured and broken apart and
 Chemical weathering where rock minerals are transformed from types that were stable when the rocks were formed to types that are now stable at the temperatures and pressures of the Earth’s surface.
Weathering produces regolith a surface layer of weathered rock particles that lies above solid, unaltered rock and also creates a number of distinctive landforms.

MECHANICAL WEATHERING

Mechanical weathering (or physical weathering) is the physical disintegration of rock material without any change in its chemical composition.
In essence, big rocks are mechanically weathered into little ones by various stresses that cause the rock to fracture into smaller and usually angular fragments. Most mechanical weathering occurs at or very near the surface, but under certain conditions it may occur at considerable depth.

Frost wedging: One of the most important physical weathering processes in cold climates is frost action. Unlike most liquids, water expands when it freezes. As water in the pore spaces of rocks freezes and thaws repeatedly, expansion can break even extremely hard rocks into smaller fragments. Even the strongest rocks cannot withstand frequent alternation of freezing and thawing. Water penetrates fractures in bedrock, if an opening in rock contains water, when the temperature falls below 0°C (32°F) ice forms, wedging its way downward. When the temperature rises above freezing, the ice melts and the water sinks farther into the slightly enlarged cavity. With renewed freezing, the wedging is repeated
 Salt Wedging:
A similar physical weathering process occurs in dry climates. During long drought periods, ground water moves to the rock surface by capillary action a process in which the water’s surface tension causes it to be drawn through fine openings and passages in the rock. This water nearly always carries dissolved salts. When the water evaporates, as it commonly does, the salts are left behind as tiny crystals. With time, the crystals grow, prying apart the rock grain by grain, much in the fashion previously described for freezing water, although less. Salt-crystal growth occurs naturally in arid and semiarid regions, but in humid climates, rainfall dissolves salts and carries them downward to ground water.
Exfoliation or Unloading:
The most widely accepted explanation of massive exfoliation is that the rock cracks after an overlying weight has been removed, a process called unloading or pressure release  .Rock that forms deep beneath the Earth’s surface is compressed by the rock above. As the upper rock is slowly worn away by erosion, the pressure is reduced, so the rock below expands slightly.
This expansion makes the rock crack in layers parallel to the surface, creating a sheeting structure. In massive rocks like granite or marble, thick, curved layers or shells of rock peel free from the parent mass below, producing an exfoliation dome.
Exfoliation occurs mainly in granite and related intrusive rocks, but under certain circumstances it is also seen in sandstone and other sedimentary strata. One of the most striking of all weathering processes is exfoliation, in which curved layers peel off bedrock.
Alternate wetting and drying.
Some clay minerals including smectite and vermiculite swell upon wetting and shrink when they dry out. Materials containing these clays, such as mudstone and shale, expand considerably on wetting, inducing micro crack formation, the widening of existing cracks, or the disintegration of the rock mass. Upon drying, the absorbed water of the expanded clays evaporates, and shrinkage cracks form. Alternate swelling and shrinking associated with wetting–drying cycles, in conjunction with the fatigue effect, leads to wet–dry weathering, or slaking, which physically disintegrates rocks.

Thermal weathering/thermal expansion/ thermoclasty:
Rocks have low thermal conductivities, which mean that they are not good at conducting heat away from their surfaces. When they are heated, the outer few millimeters become much hotter than the inner portion and the outsides expand more than the insides.
In addition, in rocks composed of crystals of different colours, the darker crystals warm up faster and cool down more slowly than the lighter crystals. All these thermal stresses may cause rock disintegration and the formation of rock flakes, shells, and huge sheets. Repeated heating and cooling produces a fatigue effect, which enhances the thermal weathering.

CHEMICAL WEATHERING.
Weathering involves a huge number of chemical reactions acting together upon many different types of rock under the full gamut of climatic conditions. Chemical reactions proceed more rapidly at warmer temperatures, so chemical weathering is most effective in the warm, moist climates of the equatorial, tropical, and subtropical zones six main chemical reactions are engaged in rock decomposition which are solution, hydration, oxidation and reduction, carbonation, and hydrolysis.

Carbonation
Occurs when carbon dioxide in water reacts with rock material to produce bicarbonate ions (HCO3–) and other ions that vary with the composition of the decomposing rock. Carbonation weathering is most effective on carbonate rocks (those containing CO3), particularly limestone, which is an abundant chemical precipitate sedimentary rock composed of calcium carbonate (CaCO3).
When water with sufficient carbon dioxide comes into contact with limestone, the chemical reaction creates calcium ions as well as bicarbonate ions. During carbonation, the calcium and carbonate in limestone detach from each other, thereby decomposing the limestone the process occurs as follows:
 H2O + CO2 + CaCO3 = Ca2+ +2HCO3–.
Water carries away the ions of calcium and bicarbonate produced in the reaction. Similar reactions take place when other carbonate rocks undergo carbonation weathering.  The process is dominant in humid climate due to role of water in the process.

Oxidation:
 Oxidation means a combination of a mineral with oxygen to form oxides or hydroxides. When the oxygen dissolved in water comes into contact with certain rock minerals, the minerals undergo oxidation, in which the oxygen atoms combine with atoms of various metallic elements making up the minerals in the rock and form new products. The new substances are usually more voluminous, softer, and more easily removed than the original compounds. When iron-bearing minerals react with oxygen (in other words, become oxidized), iron oxide is produced:
4Fe + 3O2 S 2Fe2O3 Iron Oxygen Iron Oxide (Hematite)
This reaction, probably the most common oxidation in the lithosphere, is called rusting. Because iron and aluminum are very common in Earth’s crust, a reddish- brown color is seen in many rocks and soils, particularly in tropical areas because there oxidation is the most notable chemical weathering process. Rusting contributes significantly to weathering because oxides are usually softer and more easily removed than the original iron and aluminum compounds from which the oxides were formed.

Hydrolysis: 
Is the chemical union of water with another substance to produce a new compound that is nearly always softer and weaker than the original. Igneous rocks are particularly susceptible to hydrolysis because their silicate minerals combine readily with water. Hydrolysis invariably increases the volume of the mineral, and this expansion can contribute to mechanical disintegration. In tropical areas, where water frequently percolates to considerable depth, hydrolysis often occurs far below the surface

Hydration:
Hydration is the chemical addition of water. Minerals take up water and expand; this expansion causes an increase in the volume of the material itself or rock. Calcium sulphate takes in water and turns to gypsum, which is more unstable than calcium sulphate. This process is reversible and long, continued repetition of this process causes fatigue in the rocks and may lead to their disintegration.



Solution
This process involves removal of solids in solution and depends upon solubility of a mineral in water or weak acids. On coming in contact with water many solids disintegrate and mix up as suspension in water.
Soluble rock forming minerals like nitrates, sulphates, and potassium are affected by this process. So, these minerals are easily leached out without leaving any residue in rainy climates and accumulate in dry regions.
The most soluble natural minerals are chlorides of the alkali metals: rock salt or halite (NaCl) and potash salt (KCl). These are found only in very arid climates. Gypsum (CaSO4.2H2O) is also fairly Soluble. Quartz has a very low solubility.

BIOLOGICAL WEATHERING
Biological weathering is contribution to or removal of minerals and ions from the weathering environment and physical changes due to growth or movement of organisms.

Burrowing and wedging by organisms like earthworms, termites, rodents help in exposing the new surfaces to chemical attack and assists in the penetration of moisture and air.

Human beings by disturbing vegetation, ploughing and cultivating soils, also help in mixing and creating new contacts between air, water and minerals in the earth materials.

Decaying plant and animal matter help in the production of humic, carbonic and other acids which enhance decay and solubility of some elements.

 Plant roots exert a tremendous pressure on the earth materials mechanically break them apart.
References: geography an intergrated approach by David waugh, mc knight: principle of physical geography, labaratory mannual in physical geology

CORAL COASTS
These are the coasts that are mainly composed of coral rocks/coral reefs.
A reef is a wave resistant ridge of coral, algae, and other calcareous organisms. They are formed from ex- skeleton of tiny marine organism called polyps. These organisms have ability to utilize lime from sea in building their building shells for their protection.
Coral reefs: A mass of coral is called a reef.
Polyps lives in colony and once they die their shells cement and form a ridge –like rock which is parallel to the shore.

CONDITION FOR THE GROWTH OF POLYPS.

• Warm temperature range which should be between 25°C and 29°C. Thus polyps are found on eastern side of continents where temperature is warm.
• Water should be shallow to allow sunlight penetration. Most polyps lives in water with depth less than 10 M however some species are found at the depth of 60 M.
• The water must be clear and salty.  For this reasons coral reefs are not found at river mouths because the water has silts and salty has been diluted.
• Plentiful supply of plant food (plankton) and enough oxygen.

Types of Coral Reefs.

• Fringing Reefs: Is a coralline platform lying close to the shore extending outwards from the mainland. i.e. is the platform of coral which forms when coral polyps start building a reef near the shore. The reef grows faster sea wards. Fringing reef is has a shallow lagoon usually forms between the coast and the reef.
• Barrier Reefs: is the reef separated from the coast by much wider and deeper channel or lagoon. Its base on the sea floor may be more than 60 M from the surface as this is the maximum depth at which polyps can survive. Barrier reefs are extensive compared to fringing reef. Examples of fringing reef include the one found in east African coast around Mayotte in Comoros, and Great Barrier Reef of the coast of Queensland Australia.
• Atolls: are circular reefs that rim lagoons. i.e. coral reefs are roughly circular in shape and which enclose a fairly deep lagoon. The encircling ring is usually broken in few places to allow the free flow of water. Atolls are found in mid-oceans, especially in the Indian and Pacific Oceans. These types of coral reefs exist in deep oceans where they form a circular pattern. Examples of an atoll include Aldabara Atoll, Maldive Islands, Bikini Atoll in pacific, Funafuti and Eniwetok Atoll.

THEORIES ON ORIGIN OF ATOLLS AND BARRIER REEFS.

The origin of Atolls and Barrier reefs is still a puzzle as the bases of these reefs are found at depths far beyond the one at which polyps can grow.
 Below are the theories on the origin of reefs and atolls.

1. Darwin’s theory (subsidence theory):  Darwin suggested that both barrier reefs and atolls form from fringing reef which develops around an island. An island begins to subside but the coral continue s growing upward to keep pace with the rising level of the sea. Growth was more outward than landward which over time led to formation of barrier reef. When the island was completely submerged and covered with water an atoll was formed. Recent research from oceanographers has revealed submergence of ocean floor hence prove Darwin theory to be the correct one.

2. Daly’s theory (glacial control theory):  he focused his attention on atolls only. He argued that during glacial period coral reef was not forming due to low temperatures. Thus waves and melting ice erode and reduced an island and flattened them to same level as the sea at that time.At the end of ice age temperature started to rise again and create favorable condition for coral formation. As water continues to rises coral reef also grows with relation to melting water to form atoll.

3. Murray’s theory: he suggested that the formation of barrier reefs does not involve the subsidence of ocean floor. He argued that barrier reefs start as fringing reefs. Waves pound on these reefs as they break.  The debris from the disintegrating reef accumulates on sea ward side. The accumulated material form base from which polyps accumulates and form barrier reefs.
Over time Atoll forms which is associated with subsidence of island.

1. SIGNIFICANCE OF OCEAN COASTS AND COASTAL FEATURES.
2. Influence on climate                   
3. Source of fresh water: ocean water can be distilled to get fresh water.
4. Water transport.                              
5. Fishing.
6. Minerals: Ocean water provides salts which is important mineral used both in domestic and industries.
7. Tourism: Ocean, coasts provide tourist attraction which promote tourism.
8. Source of power: ocean waves and tides have been used to generate electricity. Eg. St. Malo in North West France.

LAKES DUE TO MODE OF FORMATION

LAKES
A lake is a body of water which occupies a basin, depression or hollow on the surface of the earth. Some of the lakes are temporal while others are permanent.  The size, depth and permanence of lakes depend on the nature of the basin and availability of water (water source).
Many lakes contain fresh water and thus are referred to as fresh water lake.  However some do contain salty water. Reasons for saltiness of lake water include the following:

1. Absence of some lakes outlet in form of rivers which would drain away some of the salts contained in them. This leads to the accumulation of salts in the water.
2. In areas which are hot and dry, the rate of evaporation is very high. Due to excessive evaporation it results into concentration and accumulation of the dissolved mineral salts in the lake.
3. Some lakes do not have enough fresh water rivers emptying into them.
4. Nature of underlying rock over which the lake water is in contact with influence salinity of the lake water.

FORMATION AND CLASSIFICATION OF LAKES:
Lake classification is based on some of the criteria includes, Earth movement,  Vulcanicity, erosion, Deposition, Human activities, mass movement, falling meteorites and vegetation influence.
LAKES DUE TO EARTH’S MOVEMENT: Earths movement caused by forces originating from the interior of the earth.  Such forces results into the formation of faulting lakes and depression Lakes.

1. Faulting lakes/rift valley lakes:  a rift valley lakes are the lakes formed due to sinking of land between two parallel faults. The lakes formed are deep, narrow and elongated in character. Water collects within these formed depressions to form lakes. Example of such lakes includes Lake Tanganyika, Lake Nyasa (Malawi), Lake Rudolf, Edward and Albert.
2. Down warping lakes:  are the Lakes formed due to the warping, sagging, bending and fracturing of the earth’s crust which results into formation of depression. Once such depression occur it results into formation of Lakes when water collects on them. Example includes Lake Victoria, Lake Titicaca, Lake Superior and Caspian Sea.

LAKE FORMED BY GLACIATION:

1. Cirque or Tarn Lakes: they are the lakes formed when water occupies armed-chair shaped depression on the side of mountain called cirque. Example of tarn lakes includes teleki tarn, Red Tarn Lake in England.
2. Kettle lakes: these are depressions in the outwash plain left by the melting of masses of stagnant ice. They are irregular because of uneven moraine.
3. Ribbon /trough lake: they are the lakes which are formed when water occupy a depression in a U-shaped valley. Such lakes are narrow and elongated in shape .they are also called finger lakes. Example is Lake Ullswater.
4. Rock hollow lakes: they are formed when water occupy the depression left by rock due to glacial erosion through process of ice scouring. Such lakes are common in Finland
5. Moraine dammed lake: are the lakes formed due to glacial deposition where by glacial deposits moraine across a river valley where over time it blocks the flow of river and water collects to form a Lake.(moraine dammed lake)example lake Windermere of the lake district.

LAKES DUE TO VOLCANIC ACTIVITIES:

1. Crater and Caldera Lakes: are the lakes formed when water occupies depression formed at the summit of the volcanic mountain. The depression is the outcome of volcanic explosion. When water occupies a small depression it is called Crater Lake while when water occupy large depression on the summit it is called Caldera Lake. Example of crater lakes includes Lake Chala, lake sonanchi and lake paradise on mount marsabit.
2. Lava –dammed lakes: they are the lakes formed where lava cuts and solidifies across a river valley to block the flow of water. Thus water accumulates behind the solidified mass of lava and form a lake. Such lakes are elongated in shape as the occupy a river valley.  Example of such lakes includes Galilee Sea formed from blocking of Jordan River valley,

SOLUTION LAKES:
Karst/solution: are the lakes formed where water /rain water occupy the depression in a karst region formed due to formation of depression by chemical weathering (carbonation) process in limestone areas. Such lakes are also called karst lakes. Example Lake Scutari in Yugoslavia, Lake Guinas and Lake Ojikoto in Namibia.

WIND EROSION LAKES:
Wind deflated lakes: are lakes formed where wind deflation erode and result into formation of depression in desert. If such depressions are small and shallow pan lakes may form. But sometimes such depression goes deeper to expose water table and result into formation of Oasis lakes like in Qattara Depression in Egypt.

DEPOSITION LAKES:

1. River deposition lakes (ox bow lakes): are lakes formed where combining process of erosion on one side of meander and deposition on the other side of the mountain results into leaving behind horse shoe like depression filled with water called ox-bow Lake. Eg. Shikababu, gambi and mkunguya in river Tana.
2. Marine deposited lakes: they are also called lagoon lakes. They are lakes formed due to accumulation polyps or sands and other materials parallel but within the water near the coast. Water occupies a gap between the shore and the sea and form a lagoon. Example lake Sare, Lake Nagugabo in SW of Lake Victoria, also lake Nokoye in Benin, Ebrie in Ivory Coast.
3. Lakes due to massmovent:  they are also called barrier lakes. They are formed when mass wasting deposits materials across the river valley to cause water to accumulate. Example Lake Gormire in Yorkshire, ffynnon French.

MAN MADE LAKES:
Human made lakes includes number of lakes made by human being for different purposes. Example includes dams such as Mtera and Kidatu dams in Tanzania. Also lakes made for recreational activities such as lake gardens, Kuala Lumpur and Taiping lakes.
Also mining activities lives behind pits where once water collects into them lakes are formed.

BIOLOGICAL LAKES:
Lakes made by animals: animals such as beaver’s collects logs and other tree branches across a river valley to block flow of river hence water collects and form a lake called beaver lakes or animal lake. Example beaver lake in Yellowstone National park U.S.A.

METEORITES LAKES: they are formed due to falling of meteorites which results into formation of depression. Once such depression are filled with water are called meteorites lakes. Example Lake Bosumtwi in Ghana.

SIGNIFICANCE OF LAKES.

• Means of communication:  large lakes like the Great Lakes of North America provide a cheap and convenient form of transport for heavy and bulky goods such as coal, iron, machinery, grains and timber.
• Source of water for irrigation:  fresh water lakes provide water for irrigation in areas where agriculture is practised.eg Lake Victoria is used to irrigate sugar plantation in Kakira in Uganda.
• Generation of hydroelectric power: some lakes, especially those made by people are used in production of hydroelectric power. E.g. At Jinja Uganda.
• Source of minerals: salt lakes provide valuable rock salt.eg at Mojave Desert and Dead Sea.
• Tourist attraction and health resorts:  some lakes provide best health resorts and tourist attraction. E.g. Lake Geneva, Lake Lugano, Lake Placid (New York), Lake Vatter.
• Source of food/source of fish:  many lakes are habitat to a variety of fish species.
• Moderation of climate: large and deep lake water regulates the climate of the area surrounding. These lakes influence temperatures and rainfall of the area.
• Source of rivers: some lakes are sources of rivers, which in turn become useful in the lands through which they flow. Example River Nile whose source is Lake Victoria. Blue Nile its source is Lake Tana.
• Provision of water for domestic and industrial use: most of water (fresh water) lakes provide water which is used in homes for drinking, cooking and cleaning.
• A lake also provides storage of water. Example dams constructed by man are used as storage facilities.

NEGATIVE EFFECTS.

1. Some lakes provides habitat for disease vectors:  fresh water lakes provides habitat for the breeding of disease vectors.
2. Transport barriers: some lakes can be an obstacle to land transport.
3. Flooding: excessive rainfall can cause a lake to expand resulting in waters flooding the neighbouring shorelands.

GROUND WATER

Ground water
Refers to the water that exists below the surface of the earth (is the part of the subsurface water that fully saturates the pore spaces in bedrock, regolith, or soil).

They are found within pore spaces of the soil (soil air spaces) and in the rocks beneath the surface which are above an impermeable layer.
NOTE: water which is contained in underground (subterranean) rivers is not included in category of ground water.

Sources of ground water.

• Rain water: rain water is among the sources of ground water. When it pours onto the surface infiltrate and percolate further into the ground to make ground water. Where the rain is heavy surface run off is dominated while where rain is light water infiltrate and percolates to form ground water.
• Melt water: in springs and summer seasons regions which experiences snows and ice during  winter season, the snow starts to melt slowly in summer. Because the rate of melting is slow melted water seep, infiltrate and percolates further and forms ground water.
• Lake and sea water: also water existing on the surface of the earth in variety of forms like sea, ocean, lake, ponds, swamps and rivers partly seeps and percolates through the rocks to become ground water.
• Magmatic water/plutonic water: refers to the water which has been trapped to the rock below the surface during volcanic eruption

Types of ground water.
The types of ground water are categorized basing on the origin for their existence within the ground.

1. Connate water.
2. Juvenile water.
3. Oceanic water
4. Meteoric water

Factors influencing the existence of ground water.
Amount of ground water is the outcome of rate of infiltration and percolation. This rate is determined by number of factors including the following:

1. Precipitation: amount of rainfall received in the area determine amount of water to infiltrate and percolate into the ground. Where there is heavy rainfall with short duration most of water will be flowing as surface run-off while moderate rainfall falling over long period results into high rate of infiltration and percolation of water to the ground to form ground water.
2. Slope: infiltration and percolation of water is greater on flat areas because water collects for a long period of time enough to allow process of infiltration and percolation. On steep slope, nature of the surface favors surface run off hence little infiltration.
3. Nature of the rock: in well jointed rock or rock with pore spaces (porous and pervious rock irrespectively) water passes through pores and joints to accumulates into the ground. Thus amount of ground water is determined by permeability or impermeability of the rocks (surface rocks).
4. Vegetation cover: vegetation also plays crucial role in influencing presence of ground water. First vegetation through roots opens the soil by creating joints through which water seep into the ground. Also vegetation especially thick vegetation slow down the speed of surface run- off to allow water to infiltrate the ground.
5. Level of saturation of the ground: where the soil is dry pore spaces becomes wide enough to allow water to infiltrate and percolate into the ground to form ground water. In saturated soil pore spaces (air spaces) are filled with water thus water seepage is limited and thus surface run –off is dominating.
6. Evapo-transpiration: where there is high rate of evapo-transpiration soil becomes dry and airspaces become wide open enough to allow easy infiltration and percolation of water into the ground. On the other hand excessive evapo-transpiration reduces amount of ground water and lower the water table.

WATER TABLE.
Refers to the level of ground water bellow which all available space is filled with water. Water infiltrate the ground then percolate further down ward until it reaches a layer of impermeable rock where it saturates all available pore spaces to form saturated zone.
The upper limit of the saturated zone is called water table.
The level of saturation fluctuates depending on seasons of the year.


Underground saturation zones:
There are three main underground saturation zones which are:

• Zone of permanent saturation/phreatic zone: it is the zone where by all pore spaces are filled with water permanently.
• Zone of intermittent saturation: it is a zone where during wet season (rain season) the zone becomes saturated while during dry seasons the zone becomes dry. i.e it is a zone where water fluctuates seasonally.
• Zone of non-saturation: it is a permeable rock layer found immediately below the surface where water passes to the other zones without remaining to saturate the pores.

Both the zones of intermittent and zone of non saturation are called vadose zone or zone of aeration.
Permeable rock layer underlain by an impermeable rock layer and which is permanently saturated with water is called an Aquifer.
Presence of ground water results into the formation of springs, wells and artesian basins.
SPRINGS
A spring is a point or place where underground water flows out naturally onto the land surface. They occur where water table has been exposed onto the surface.
Some springs are temporary while others are permanent and are the source of some rivers.
Ways in which springs occurs:

1. A spring can occur where permeable rock overlies impermeable rock and where water table is exposed onto the surface at the hillside.
2. Spring can occur at the foot of the scarp slope or dip slope of cuesta. if spring occurs at the scarp slope it is called scarp slope spring while if it occurs at dip slope it is called dip slope spring.
3. A spring can also occur along a fault where permeable rock layer has been brought against an impermeable rock layer. Such spring is called fault spring.
4. A spring can occur in a well jointed rock where water infiltrate and percolate through rock joints and later came to be exposed and flow onto the surface through other rock joints. Such  springs are called rock jointed springs
5. A spring may occur in area where an aquifer lies on the upper part of outcropped dyke. Water flow out onto the surface to form a spring called dyke spring.
6. A spring may occur where limestone escarpment is underlain by an impermeable layer; a spring may form at the foot as water table meets the surface causing water to oozes out as spring.

Wells and boreholes:
They are deep holes dug in the ground often with the purpose of getting water. A well can be permanent if it has been sunk deep bellow to a zone of permanent water saturation. And it can be temporary if it as been sunk to a zone of intermittent saturation.
ARTESIAN BASIN
Artesian basin is a saucer-shaped like depression which consists of a layer of permeable rock that is sandwiched between two layers of impermeable rock. It forms broad syncline with either ends or one end of the permeable rock exposed onto the surface.
Rain water enters artesian basin through exposed ends of permeable rock layer and saturate to for aquifer.
Artesian well: it is a well which has been sunk into an aquifer of artesian basin where water comes onto the surface due to hydraulic pressure.
Necessary conditions for the formation of artesian wells.

• The permeable rock layer(aquifer) must be enclosed between two layer of impermeable rock.
• Either one or both sides of the aquifer must be outcropped in region which is a source of water.
• The mouth of artesian well must be lower than the intake area. This allows the water to be forced to the surface by pressure.
• The aquifer must dip from the region of water intake and the rock layers must form a broad syncline or basin.

Significance of groundwater:

1. Source of rivers: some rivers originates from natural springs which are consequence of ground water.
2. Source of water: ground water provide water for industrial activities.
3. Agriculture
4. Settlement
5. Provision of hot water
6. Tourist attraction
7. Source of minerals.