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CSS Syllabus: 2. LandformsMajor landforms, Rocks : origin, formation and classification. Internal Structure ofthe Earth. Earth quakes and Volcancity. Weathering. Mass Wasting. Erosion and

e!osition. "ycle of Erosion. #andforms !roduced $y %nderground and &roundWater. Wind and &laciers.

Landforms

Definition: #andforms are defined as the natural !hysical features found on thesurface of the earth. #andforms are created as a result of the 'arious forces ofnature such as (ind, (ater and ice and also $y the mo'ement of the earth)stectonic !lates. *or e+am!le, due to these actions, the soil gets eroded andde!osited some(here far from the site of erosion, thus leads to the formation ofdifferent landforms. Some landforms are created in a matter of fe( hours otherstake millions of years to a!!ear. - grou! of landforms in a !articular area is

called its landsca!e.

Types and Characteristic Features of Landforms

here are many ty!es of landforms on the earth)s surface. Each landform ischaracteri/ed $y its slo!e, ele'ation, soil and rock ty!e, stratification andorientation. *ollo(ing is the list of some of the common ty!es of landforms andtheir characteristics:

Mountains: Mountains are areas, (hich are higher than the surrounding areas

and are characteri/ed $y a !eak, e.g. he 0imalayas. Sur!risingly, they are morefrequently !resent in the oceans than in land. - mountain is stee!er than a hill.Mountains are formed due the tectonic mo'ement such as an earthquake or a'olcanic eru!tion. - fe( are resulted due to erosion of the surrounding areas $ythe action of (ind, (ater or ice.

Plateaus: 1lateaus are large highland flat areas se!arated from the surroundingareas $y a stee! slo!e, e.g. he i$etan !lateau. 1lateaus are formed due to'arious actions such as collision of the earth)s tectonic !lates, u!lift of theearth)s crust $y the action of magma some are resulted due to the la'a flo(

from the 'olcanic eru!tion.

Islands: Islands are areas that are com!letely surrounded $y (ater, e.g. he0a(aiian Islands. Islands are formed either as a result of the 'olcanic eru!tion ordue the !resence of hot s!ots on the lithos!here.

Plains: 1lains are flat areas or lo( relief areas on the earth)s surface, e.g.!rairies, ste!!es. 1lains are formed due to the sedimentation of the eroded soilfrom the hills and mountains or due to the flo(ing la'a de!osited $y the agentsof (ind, (ater and ice.

alleys: Valleys are flat areas of land $et(een the hills or mountains, e.g. he

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"alifornia "entral Valley. Mostly they are formed $y the actions of ri'ers andglaciers. e!ending u!on the sha!e, 'alley forms are classified as %2sha!ed orV2sha!ed 'alley. V2sha!ed 'alleys are formed $y flo(ing (ater or ri'ers, (hereas%2sha!ed 'alleys are formed $y glaciers.

Deserts: eserts are 'ery dry lands (ith little or no rainfall, for e+am!le, heSahara desert. Mostly deserts are formed in rainshado( areas, (hich arelee(ard of a mountain range (ith res!ect to the (ind direction. hus, themountains $lock the !assage of (ind resulting in little or sometimes no rain.

Loess : #oess are de!osits of silt and (ith a little amount of sand and clay. Manya times (ind action is res!onsi$le for formation of loess ho(e'er sometimesglacial acti'ity can also form loess.

!i"ers: Ri'ers are natural flo(ing stream of fresh(ater, e.g. he 3ile. hey

mostly flo( to(ards lakes or oceans $ut sometimes they dried u! (ithoutreaching another (ater $ody. Ri'er (ater is collected from the surface (aterrunoffs, ground(ater (ater recharge and sometimes from the (ater reser'oirssuch as glaciers. #andforms definitely !lay an im!ortant role in the formation ofri'ers.

#ceans: 4ceans are the $iggest form of (ater and are saline, such as he1acific 4cean. 4ceans of the (orld co'er around 567 of the earth)s surface andcontrol the (eather and climate of the earth)s surface. 4ceans are originateddue the "ontinental rift, i.e. the mo'ement of the earth)s tectonic !lates.

$laciers: &laciers are huge slo( mo'ing $ody of ice. &laciers are formed due tothe com!action of sno( layers and mo'es (ith res!ect to gra'ity and !ressure.Mainly there are t(o ty!es of glaciers 2 -l!ine glaciers, (hich are formed in highmountains and "ontinental glaciers, (hich are formed in cold 1olar Regions.

Types of %rosion

here are four main ty!es forces that cause the erosion of solid rock andformation of sediments:

&. 'ater 2 as running (ater or (a'e action2. 'ind 2 occurs in t(o forms: deflation and a$rasion(. $laciers 2 $y scra!ing rock and trans!orting all si/es of sediment thousandsof miles). $ra"ity 2 as a constant force on unsta$le hills and cliffs

'ater

1o(erful currents of mo'ing (ater can $e 'ery destructi'e forces of nature. here are t(o (ays in (hich (ater can act as a trans!ort of sediment: $yrunning (ater, such as ri'ers and streams, or $y (a'es. Included (ith erosion $y

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running (ater is erosion due to hea'y rainfall. 0ea'y rainfall can cause sedimentto $e dislodged due to the im!act of continuous high2'elocity raindro!s or it cancause flooding, (hich causes erosion in the same manner as ri'ers and streams,also kno(n as sheet erosion. Vegetation is 'ery im!ortant for slo(ing do(nerosion due to hea'y rainfall and flooding. he lea'es and $ranches of trees slo(do(n falling raindro!s $efore they im!act the surface. Moreo'er, a (ell2de'elo!ed net(ork of tree, $ush and grass roots holds soil in !lace.

Ri'ers and streams erode and trans!ort sediment $y !icking u! !articles alongthe channel or at the $ottom of the channel. he a$ility for streams to trans!ortsediment de!ends on the tur$ulence and 'elocity of the (ater. he higher the'elocity of the (ater, the more tur$ulence, and therefore the more effecti'e the(ater is a$le to carry !articles do(nstream. he 'elocity of the (ater isgenerally greater as the de!th increases. herefore, larger !articles aretrans!orted $y (ater at de!th (hereas (ater at the surface trans!orts fine

!articles. his is e'ident in stream and ri'er $ed de!osits, (here coarser2grainedmaterial is found at the $ottom of the stream and finer2grained material is foundalong the edges.

'ind

#ike (ater, erosion due to (ind !rocesses is de!endent on the rate of s!eed the(ind is $lo(ing or for ho( long a rock formation has $een su$ject to (ind. -lsolike (ater, (ind erodes in t(o (ays: $y a !rocess called deflation and $y another

!rocess called a$rasion. eflation comes from the #atin (ord meaning 8to $lo(a(ay9. -s the name im!lies, deflation occurs (hen the flo( of air is strongenough to !ick u! !articles and $lo( them else(here. -reas of significantdeflation are deserts and $eaches, (here little to no 'egetation is !resent to!rotect sediments from the forces of (ind. -$rasion occurs (hen (ind2dri'ensediments strike and chi! a(ay at rock. he rock $eing a$raded $egins to takeon distincti'e forms and can e'en $e slightly !olished.

$laciers

&laciers are some of the most !o(erful trans!orters of sediment. hey do not

discriminate $et(een the si/es of !articles $eing trans!orted and can trans!ortany si/e !article thousands of kilometers. here are multi!le (ays in (hichglaciers erode rock surfaces and formations. In one (ay, glaciers act like huge$ulldo/ers, !icking u! loose sediment from silt and sand to huge $oulders and!ushing it along to $e de!osited else(here. -nother (ay is like a file, literallyscratching and scra!ing a(ay at rock formations, lea'ing marks called striationsin its !ath. his occurs (hen the sediment at the $ase of the glacier is scra!edagainst $edrock. In the case of huge $oulders, the scra!ing can $e much moredramatic and large chunks of rock can $e ri!!ed a(ay.

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i# i$ o##urs and $ " p"riod o; $im" o&"r i# i$ as o##urr"d< Mass *astin+ and +ra"ity

Mass (asting, the do(nhill mo'ement of soil and rock under the influence ofgra'ity, encom!asses a 'ariety of !hysical !rocesses $y (hich mountain rangesare eroded. hese !rocesses include

, Creep 2 slo(, nearly continuous do(nslo!e mo'ement that is induced $y eitherfree/e;tha( cycles or (et;dry cycles.

, Slides 2 sudden do(nhill mo'ement of masses of rock or sediment., Debris flo*s 2 dense, fluid mi+tures of rock, sand, mud, and (ater

here are other categories of mass (asting !rocesses such as slum!s, rockflo(s, rockfalls, $lock glides

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!rocesses are classified as erosional !rocesses, (hich include all !rocesses thatremo'e and trans!ort (eathered or un(eathered soil and rocks. Erosional!rocesses include

, 'ind, !unnin+ *ater, 'a"es, $laciers, 'ater flo*in+ under+round, $ra"ity-dri"en processes mass-*astin+/

Mass2(asting !rocesses such as cree!, landslides, and de$ris flo(s aredistinguished from each other in !art $y (hether they occur ra!idly or slo(ly.#andslides are ca!a$le of trans!orting massi'e amounts of rock and soildo(nslo!e for miles in 'ery short !eriods