InsightsUnveiled

Weathering refers to the breakdown and disintegration and decomposition of rocks in situ through mechanical and chemical changes in rocks and their minerals affected by water,temperature,wind different  atmosphereic gasses etc. provided there is no large scale transport of weathered products by denudational processes except mass movement of rock wastes.           When the temperature of solid is increased/decreased it expands or contract.the commonly used index in weathering studies to record the degree of their response to temperature changes is called coefficient for linear thermal expansion. It is quite complicated for rocks, particularly at the mineral(crystal) scale. Individual crystals have varying coefficients. Even single crystal coefficients may vary with the direction of measurements. The formula for coefficients for linear thermal expansion is : moreover, the composition of a mineral surface is not the same as th...

Joints are small scale fractures that result when a rock shows brittle failure under the tensional/shearing stress. Rock cleavage consists of fractures along closely spaced parallel surfaces and is due to preferred orientation of platy minerals closely spaced parallel surfaces and is due to a preferred orientation of platy minerals such as mica, muscovite etc. Degree of cleavage depends upon the mineralogy of deforming rocks and on the magnitude  of applied stress. It influences weathering as it allows water to penetrate along the fractures, which are planes of mechanical weaknesses. Tensional stresses tend to produce joints that are open and provide zones of ready water movement. Shearing stresses tend to result in joints that are tightly closed and much less permeable. The openness of joints may be called 'thickness'.  Two other geometrical characteristics affect the response of jointed rocks:- 1) joint spacing expressed as average distance between the joints. The c...

chemical weathering is decomposition and disintegration of rocks due to chemical processes and reactions wherein the minerals of the rocks weather away.The rates of weathering due to chemical reactions are not well understood generally in thermodynamic aspects.then there is the effect of temperature on the yeilds,which can be predicted by using the Le chatelier's principles. the effect of a temperature increase on rection rates is to increase them.An approximte rule is that for every increase of 10(degree)Centigrade the reaction rate is doubled.The quantitative relation between temperature and wethering rate is governed by Arrhenius equation. The various reactions leading to weathering are as follows:- 1) Hydration:- It is an exothermic reaction.It does not involve reaction with water but on association between ions and water mollecules.Vo bnds are broken in this process.Indiavidual polar water moleculaes orient themselves to charged moneral surface in a way that one end of a...

Wind blankets the sandy deserts and strips  hundreds of the millions of tonne of dust each year.It was more effective in the past(example:-Mesozoic era) than today.wind is more effective indeserts in the wetter environments not because it blows with greater strength in the former than in the latter but due to the separate reasons:- a)Dry surfaces;& b)sparse vegetation. a) Dry surfaces :- moisture and mobility- when the interstitial spaces between particle pores are saturated,loose surface particles are partially exposed to the drag and lift forces  of the wind.Surace cohesion holds the particles tightly which is maximum when the meniscues are tightly curved out  and they extend  over maximu grain surface .drying breaks meniscuses and cohesion teminates making surface particles  more  and more vulnerable to drag and lift forces of the wind.moisture  increases threshold of movement. rule-of thumb estimates choose 4% water content as limit...

It's the most widespread evidence of subglacial action and is a rolling low relief plain.It covers vast areas and are indicative of typical non-landforming or bed forming aspect of subglacial processes.Across the till plains we find distinctive features like: 1)Thrust block ridges; 2)Depressions; 3)Push ridges which show localised subglacial glacial differential stress,local variations in sedimentrheology or the influence of topographic control.             their  formation is due to widespread uniformity of subglacial depositional conditions which however,does not signify uniformity of the till type.The sediments of the till plain give a complex reflection of the local and regional bed geology,topography,ice dynamics and subglacial bed conditions. Other features found over large or restricted area of the till plains are :- a)Lodgements; b)Meltout; c)Flow tills; and d)Melange,which contain rafted units of ...

It's an isolated hill,left as a residue of the limestone at the polje floor named from the village of 'hum', in the nation of yugoslavian karst.They are often conicle or pyramidal in shape with uniform slopes,but those in the alluvium tend to be more convex profiles with basal steepening of their sides.Asymmetry in the residual hills has been attributed to greater rainfall and the solution on windward eastern sides,giving gentler slopes there(northern Peurto Rico) as per thorp's view point.            Dianric karst feature based on the scheme of Civijic is perhaps the best,where hums form when elaborate cave systems eat into the karst margins and the poljes causing destruction of the karst and causing reappearance of normal valleys.steepheads recess karst margins and the poljes are planed afresh at the lower levels forming some hums.

Texture is the relationship between the mineral grains that form a rock.two types of texture are significant for weathering:- 1) Crystalline texture :-such textured rocks are weathering resistant,generally.It has high resistance to stress,shows a large range of elastic behaviour and has low porosity(example:-0.1% in case of granite).a variety of it is the poikilitic texture ,Which occurs when  a large crystal completely encloses one or more smaller crystals within it. 2) Sedimentary  texture :-This is particularly important because sedimentary rocks underlie 80% of continental surface.Here,the component particles do'nt show interlocking characteristics. Grain size affects the amount and potential activity of the water through it's relationship with sorting,porosity and surface area.a high porosity suggests large water content.A large surface area implies an extensive interface between the water and the grain and so enhanced chemical weatheri...

Weathering controlled landforms are those whose formation is dominated by process.Erosional,depositional and complex varieties may be identified. Erosional varieties are formed when the weathering selectively attacks bedrocks.If the transporatation complex is linked to the weathering process then an erosional,weathering generated landform may be recognised.example:-removal in solute form of bedrock,removal of material by action of lichen and algae. Depositional types are formed when transportation process,form landforms,acts on the results of weathering.Example:-scree. In Complex type weathering plays a major role but unrelated transport process actually generate relief.Example:-tor. erosional forms:- a)Microforms:- Smaller erosional landforms can not be atributed to a single process.chemical alteration may exploit an existing weakness (perhaps a set of microcracks) and may be associated with biological weathering ,often due to lichen colonisation.uder a suitable conditions...

Physical weathering refers to the disintegration of the rocks due to temperature variations,frost actions,wind etc. there are 6 such processes:- a)Low temperature based weathering:- 1) Freeze-thaw weathering:- this is the process which occurs when the water freezes and expands in volume within the rocks. a) by freezing of 'in-place' water:- When water freezes a 95% volumetric expansion takes place because water molecules take a hexagonal arrangement which occupies more space than their relatively close packed distribution in liquid phase.this expansion generates a pressure of 207 MPa (a theoretical pressure),at -22 degree Celsius under the optimum conditions,against the containing walls in a closed system.this pressure is much greater than rock tensile strength,which is rarely more than 10 MPa.Even if theoretical pressure is not reached,the actual stress generated are sufficient to shatter rocks. b) By water migration and ice growth:- This model is dyna...

Kegel karst is a German word and is one of the 3 subjects of the overall category of polygonal karst distinguished by Williams .It's a type of tropical karst.It is known for it's hemispheroidal and sinusoidal hills and star-shaped depressions.  Lehmann ,originally designated it.It is also corresponds largely to a cockpit country of Jamaica and Puerto Rico.there is relative relief of 30 - 120 m and a density of 15 - 30 Km. sq..The cone form is not the most characteristic feature of the area.                        Turm karst or tower karst is also a karst feature of tropics.It's formation is controlled by structures over the lithology and specific solutional processes.As per Balazs's observation they are steep sided residual rising like islands from the plain.they are 100 m - 300 m. high and runs 5-10 Km.sq. they are formed by engulfment of the surrounding ...

Channel pattern mean the configuration of a river as it would appear from an airplane 3 patterns have been identified,one of which is the braided channel pattern.                            A braided channel or stream is one characterized by a network of interconnected converging and diverging channels resembling the stands of a bread.The whole river system is generally shallow,so that intervening single bars and alluvial materials are exposed at low waters.It is mainly due to non-coherence of load,which leads to selective deposition and the alluvial material is exposed at low waters.                           The development of braiding stream is a type of adjustment that a channel makes due to possession of debris load too larg...

There is a close relationship between braided stream and meanders.Example:-The ana branches of a braided stream definitely meanders.On the basis of the works by European engineers, Lelivesky(1955) concluded that meanders are the result of helical flow. Although this mechanism has been important but it isn't clear how helical flow is related to the width,curvature and length of the meanders.                                 According to Matthes ,bank cutting and orderly transfer of sediment to it's place of deposition on the point bars were simple requirements for the meandering Friendkin's concept is essentially identical.     A meander can't exist if the banks were unerodible or if they were completely unstable.The meander pattern of melt water channels on the surface of ...

Drumlins   are roughly ovoid shaped hills of dominantly glacial debris that typically occur within groups or fields of several thousand.They exhibit very strong Enechelon long axis preferred orientation paralleling the main direction of ice flow.The classical drumlins have steeper stross-end slope  and tapered lee-side.Limited relationships appear between drumlins and topography.the topographic locations within which the drumlins are found are many and varied.Drumlins are composed of vast range of sediment types although previously it was thought to be exclusively formed of subglacial Till.Drumlin shapes vary enormously and may reflect post-depositional sub-aerial mass movement. At present 3 main drumlin forming hypothesis are present:- a) Formation by moulding of previously deposited material within a sub-glacial environment ,in which a limited amount of sub-glacial melt water activity occurs which influences moulding and deformational processes  produc...

Cockpits are formed in humid tropical karst regions where simple closed depressions which have convexly inward lobed sides,making them star shaped,with gullies carrying streams after heavy rains are found.They are set among steep residual hills.                         Lehmann   gave an interpretation of the development of humid tropical karst evolution i.e., development of the 'cockpit country'.A prior planation is gently domed, tectonically which rejuvenated surface drainage,which produced ridges and valleys which align down the flank of the dome.This is followed by the development of vertical infiltration and underground drainage causing valleys to breakup into chains of star shaped closed depressions of surface solutional origin.thus,there is centripetal fluvial action supported by rainstorms of ...

Wind erosion is largely controlled and determined by- wind velocity,nature and amount of sands dusts and pebbles,composition of rocks,nature of vegetation,humidity,rainfall amount  and temperature.Wind erosion is believed to be defective only upto 182 cm. above the earth's surface.Maximum wind erosion occurs at a short distance above the ground,say at a height of 20-25cm. because here the wind velocity and sediment movement are moderate whereas at the ground sediment transport is high but velocity of transportation is low.At a height the velocity is high but quantity of sand available for abrasion is small.Due to their variable direction they erode rocks from all directions. There are erosional processes:- a) Deflation:-(derived from the Latin word 'deflatus' meaning blowing away) It includes removing,lifting and blowing away dry and loose particles of sands and dusts i.e., incoherent sediments,by wind.It is controlled by 3 factors:- 1) Surf...

there are 3 processes of deposition (sedimentation,accretion and encroachment) as it is in case of erosion and transportation.Deposition of sand depends on the variations in wind speed,grain size and type,type of obstacle in the path of the wind(i.e.,trees,bushes,lakes etc).Sand is deposited on both windward and leeward side of the obstruction.Accumulated sand mounds on the either side of the obstruction are called sand shadows . sand drifts are sand accumulations between obstacles. there are 3 types of depositional landform in arid region.they are:- A)Sand ripples; B)Sand dunes; C)Loess. A) Sand ripples:- they are small scale depositional features of sand covering most dry,bare sandy surfaces in the deserts.Heights vary from 1cm. - 3cm.; windward slope angle between 8 degree and 13 degree and in extreme 25 degree.their summits are broadly convex with the lee faces having angles upto 30 degrees.some of them have either sharp or smooth brinks. there are 3 mai...

Glacier not only performs erosive and transportational activity but also depositional activity.    Till is a type of a sediment in which the components have been brought into contact by direct agency og the glacier ice. Inspite of the subsequent glacially induced flow  it does'nt become disaggregated.It's a glacial deposit.there has been little or no sorting by water.       The most widespread evience of the subglacial action is the formation of rolling,low relief till plain,covering vast areas and are indicative of the non-landforming -thrust block ridges,depression and push ridges can be found which reflect localised subglacial differential stress,local variations in sediment rheology or influence of topographic control.they have formed due to uniformity of sunglacial depositional conditions.however,they do not signify till type uniformity.It's sediments are complex reflections of the local and regional bed geology,topography,ice dynamic...