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Wednesday, March 24, 2010

geography short notes -3

EOLINE PROCESSES

it is the processes pertain to the activity of the winds & more specifically , to the winds ability to shape the surface of the earth & other planets. winds may erode transport & deposit minerals & are effective agents in regions with sparse vegetation & large supply of unconsolidated sediments . this process are important in arid environments such as deserts . wind erodes the earth's surface by deflation , by the removal of loose, fine-grained particles , by the turbulent eddy action of the wind & by abrasion. regions which experience intense & sustained erosion are called deflation zone. most of Eoline deflation zones are composed of the desert pavement, a sheet-like surface of rock fragments that remains after wind & water have removed the fine particulars, a dark, shiny stain called desert vanish is often found on the surface of some desert rocks that have been exposed at the surface for a long period of time. shine stain minerals are manganese, iron oxides, hydroxides, clay. deflation basins , called blowouts are hollows formed by the removal of particles by wind . wind-driven grains abrade landforms. sculpted landforms , called Yardangs, are up ot tens of meters high & kilometers long are form that have been stremlined by desert winds.

ERG LANDFORM

an erg is also known as duna sea is a large relatively flat area of desert covered with wind-swept san with little of to no vegetation cover. the term takes its name from the Arabic word erg mean "dune field". an ergis defined as to be a desert area that contains more than 125 square kilometers of eolian sand & where sand covers more than 20% of the surface approximately 85% of the earth's mobile sand is found in ergs that are larger than 32,000 km2. ergs are als found on other celestial bodies, such as venus & saturn's moon titan. erg are concentrated in 2 broad belts between 20 degree-40 degree S latitutdes, which includes regions crossed by the dry, subsiding air of the trade winds. averaged erg are limited to regions which receive not more than 150 mm of annual precipitation. sand sea & dune fields generally occur in regions downwind of copious sources of dry, loose sand, such as dry riverbeds , deltas, flood plains, glacial out wash plains, dry lakes & dry beaches. at least 1 million years are required to build ergs with very large dunes sand sea that have accumulated in subsiding structural & topographic basins, attain great thickness more than 1000m. by nature ergs are very active. individual dunes forming ergs typically have width, length / both dimensions greater than 500m.

ESKER

it is a long , winding ridge of stratified sand & gravel. these are frequently several miles in length, most of esker are believed to form in ice-walled tunnels by streams which flowed within & under glaciers. after the retaining ice walls melt away, stream deposits remain as long winding ridges.it it is also form above the glaciers by accumulation of sediment in supraglacial channels, increvasses, in linear zones between stagnant blocks, the rate of plastic flow & melting of the basic ice determines the size & shape of the subglacial tunnel. this in turn determines shape, composition, structure of Esker. they are no often found as continuous ridges, but have gaps that seperate the winding segments. the ridge crests of eskers are not usually level for very long & are generally knobby. Eskers can be borad-crested / sharp-crested with steepsides. they can reach hundreds of kilometers in high. the concentration of rock debris in the ice & the rate at which sediment is delivered to the tunnel by melting & from upstream transport determines the amount of sediments in Eskers. the sediments consists of coarse-grained, water-laid sand & gravel. cross-bedding is common in Esker.

the name Esker is derived from Irish word eiscier means " a ridge of one seperating two plains surfaces". the mason esker at 22 miles is one of the longest Esker in the US.


EXCAVATIONS IN INDIA AND THEIR EXCAVATORS

1.Harappa-1921(Montgomery) -- Dayaram sahani
2.Mohanjadaro-1922(Sindh) -- Rakhaldas Banerjee
3.Kalibangan-(Hanumangar) -- Amalananda Gosh
4.Lothal-1957(Ahmedabad) -- S.R.Rao
5.Bonwali-1973(Hissar) -- R.S.Bist
6.Rangpur-1931(Gujarat) -- M.S.Vatsa
7.Ropar-1955(Punjab) -- Y.D.Sharma
8.Alamgirpur-(Meerut) -- Y.D.Sharma
9.Kotdiji-1935(Sindh) -- Ghurey
10.Surkotada-(Gujarat) -- J.P.Joshi
11.Changudaro-(Sindh) -- Majumdar
12.Sutkagendor-(Baluchisthan) -- A.Stein

FACTS OF RHINE

Introduction :
Rhine is the of the largest at river in Europe. it runs for over 1300 kilometers from its source in South Rhine flows on through France, Germany & Netherlands.
* back bone of Europe = Rhine
* Rhine originates from = Gothar
* Rhine enters rift valley at = Basle
* Rhine drains into = North sea
* Tributaries of Rhine = Mosel, main, Lippe.

international co-operation over the river Rhine goes back to 1887 with a treaty prohibiting the discharge of wastes dangerous to fish. international commission for the protection of the Rhine against pollution was formed. most recently, after a serious incident in 1986, the Rhino Action Programme was developed , by the 2000, programme aims to achieve a return to the river species such as the salmon which once thrived them. the use of the river of extracting drinking water is also dafeguarded.

The specific aimes of the Rhine Action Programme Approved by a confluence of ministers on the protection of the Rhine against Pollution, in Strasbourg in 1987 are :

- to accelerate the reduction of permanent pollution from all sources.
- to reduce the risk of accidents & spillages.
- to improve hydrological & other conditions of the river.

At The National Rivers :

- national laws are made starting how much waster material can be discharged.
- industrial plants are obliged to have a permit for their emissions.
- pollution taxes are imposed on individuals & industrial plants
- purification & measuring stations are built.

At International Level :

- there is nore co-operation between countries that share the Rhine
- there is an alaram system for every time the concentration of a certain material exceeds its permitted value.
- plans are made for the conservation & restoration of natural landscapes.

FELDSPAR

it is the name of a group of rock-forming minerals which make up as much as 60% of the earth's crust. crystallize from magma in both intrusive & extrusive rocks, & they can also occur as compact minerals as veins & are also present in many types of metamorphic rock . rock formed entirely of plagioclase Feldspar is known as northosite. they are also found in many types of sedimentary rock. it is typically reddish / pale pink in color, & has a hardness of 60 the mohs scale.

feldspar is derived from the german word feld, field, spat ; a rock that does not contain ore. feldspar refers to minerals that contains feldspar.

COMPOSITION :
this group of minerals consists of framework or tectosilicates . composition of major elements in common feldspar can be expressed in term of 3 endmembranes.

K-feldspar endmembranes = KAlSi3O8
Albite endmembranes = NaAlSi3O8
Anorthite endmembranes = CaAl2Si2O8

- sodium solution between K-feldspar & albit are called alkali feldspar.
- solid solution between albite & anorthite are called plagioclase.
- sanidine, orthoclase, microline refer to polymorphs of K-feldspar.

- sanidine is stable at the highest temperature
- microline at the lowest perthite is typical texture in alkali feldspar, due to exsolution of contrasting alkali feldspar compositions during cooling of an intermediate composition. the perthitic texture in the alkali feldspar of many granites are coarse enough to be visible to the naked eye.

USES :
- feldspar is common raw material in the production of ceramics.
- feldspar are used for thermoluminescence dating & optical dating in earth science & archeology.
- feldspar is often an anti-eating agent used in powedered forms of non-dairy creams.


FLASH FLOOD

it is rapidly flooding of geomorphic lowlying areas- washes, rivers & streams -- caused by the intense rainfall associated with a thunder strom, or multiple thunder storms. they are distinguished from a regular flood by a timescale less than 6 hours.

CAUSES

it occurs when the ground becomes saturated with water that has fallen too quickly to be absorbed. they mostly often occur in dry areas that have recently received precipitation, these are extremely dangerous because of their sudden nature.


FOEHN WIND

this occurs when a deep layer of prevailing wind is forced over a mountain range. as the wind moves upslope, it expands & cools, causing water vapour to precipitate out. this dehydrate air then passes over the crest & begins to move downslope. Foehn winds can rise temperature by as much as 30 degree C , 54 degree F in just a matter of hours.

EFFECTS :

winds of this type are called "snow-eaters" for their ability to make snow melt rapidly. this ability is based not only on high temperature, but also the low relative humidity of the air mass. Foehn winds are often associated in popular mythology with illness ranging from migraines to psychosis.

the name Foehn came from German, originated in the alpine region.

Foehn winds are called in different names in different countries. they are :
- Zonda winds in Argentina
- Chinook in USA & Canada
- the Nor'Westr in Hawkes Bay
- Halny in Carpathian Mountain, Eastern Europe
- Fogony in the Catalan Pyrenees
- Berg wind in South Africa
- Viento Sur in the Cantabrian region of North Spain
- Terral in Malaga Souhtern Spain
- Foehn wind in Austria, southern germany.


FUMAROLE

it is an opening in earth's crust , often in the neighbourhood of volcanoes, which emits steam & gases such as carbon dioxide, sulfur dioxide, hydrocloric acid & hydrogen sulfide. the name solfatare , from the italian solfa sulfur, is given to fumaroles that emit sulfurous gases.fumarole may occur along tiny cracks or long fissures, in chatic clusters or fields & on the surface of lava flows & thick deposites of pyroclastic flows. a fumarole field is an area of thermal springs & gas vents are releasing gases or interacting with groung water from the perspective of ground water. fumarole could be described as a hot spring that boils off call its water before the water reaches the surface example famous valley of ten thousand smokes , which was formed during the 1912 erruption of novarupta in alaska.    

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