So, we are starting with world physical
geography, which was already mentioned in the schedule. Here we have given a
brief outline of what we are going to cover in the upcoming module.
Basic
concepts (Geomorphology)
To understand the interior of the
Earth
1. Crust – The
outermost layer, or shell, of the earth (or any other differentiated) planet.
Earth’s crust is generally defined as the part of the Earth above the
Mohorovivic discontinuity. It represents less than one per cent of Earth’s
total.
2. Mantle – The zone
of earth’s interior between the base line of the crust (the Mohorovivic (Moho)
discontinuity) and the core. The mantle has an average density of about 3.3g/cm3
and accounts for about 68 per cent of earth’s mass. The mantle lies
between the crust and the core of the earth. The lower layers of mantle are
floored by the Gutenberg discontinuity.
3. Core – The
central part of the earth below the depth of 2900 Km.
4. Mohorovivic (Moho) Discontinuity
– The first global seismic discontinuity below the surface of the Earth. It
lies at a depth varying from about 5 to 10 km beneath the ocean floor to about
35 km beneath the continents, commonly referred to as the Moho.
5. Vulcanicity
– The movement of magma, both into earth’s crust (intrusion) and onto Earth’s
surface.
6. Magma – A mobile
silicate melt, which can contain suspended crystals and dissolved gasses as
well as liquid.
7. Silicate (silicate minerals)
– A mineral containing silicon oxygen tetrahedral, in which four oxygen atoms
surround each silicon.
8. Seismology
– It is the science which study various aspect of seismic waves, generated
during the occurrence earthquakes.
9. Seismic waves
– The different types of tremors and waves generated during the occurrence of
an earth quake are called seismic waves.
10. Seismograph
– Seismic waves are recorded with the help of an instrument known as
seismograph.
11. Sial – A
general term for the silica – rich rocks that form the continental masses.
12. Sima - A
general term for the magnesium – rich igneous rocks (basalt, gabbro and
peridotite) of the ocean basin.
13. Nife – It is
located just below ‘sima’ layer.this layer is composed of nickel (NI) and
ferrium (Fe).
14. Lithosphere
–It is having thickness of about 100 km is mostly composed of granites. Silica
and aluminium are dominant constituents. Average density is 3.5.
15. Pyrosphere
– It stretches for a thickness of 2780 km having an average density of 5.6. The
dominant rock is Basalt.
To
understand the continents and ocean basins
1. Continent - A large landmass, from 20 to 60 km thick, composed mostly
of granitic rock. Continents rise abruptly above the deep – ocean floor and
include the marginal areas submerged beneath sea level. Examples – the African
continent, the Asiatic continent, the North American and South American
continent, etc.
2. Basin – A depression into which the surrounding area drains.
3. Plate- The rigid
lithospheric slabs or rigid and solid crustal layers are tectonically called
plates.
4. Plate tectonics – The whole mechanism of the evolution, nature and
motion of plates and resultant reaction.
5. Constructive plate margins- these are also called as ‘divergent
plate margins’ or ‘accreting plate margins’. Constructive plate margins
(boundaries) represents zones of divergence where her is continues upwelling of
molten materials (lava) and new oceanic crust is continuously formed.
6. Destructive Plate margins – these are also called as
‘consuming plate margins’ or ‘convergent plate margin’ because two plates move
towards each other or two plates converge along a line and leading edge of one
plate overrides the other plate and the overridden pate is subducted or thrust
into the mantle and thus part of the crust (plate) is lost in the mantle.
7. Sea floor spreading – The theory of that the sea floor
spreads laterally away from the oceanic ridge as new lithosphere is created
along the crest of the ridge by igneous activity.
8. Pangaea - About 700million years ago all the land masses were united
together in the form of one single giant land mass known as Pangaea.
9. Isostasy – The continental crust of earth has a visible part above
the surface and lower, in visible one. The balance between these two is
Isostasy. If part of the upper surface is removed by erosion, the continental
crust will rise to offset this erosion, at least in part. Section of the
continental crust have been pushed down by the weight of glacial ice, the
extent of depression varying with the thickness of ice, and the density of the
material below. It is believed that the critical size for an ice cap to depress
a landmass is a 500km diameter. Landmass will rise again if the ice melts.
To understand the Movement of Earth
1. Endogenetic forces – the forces coming from within the
earth are called as Endogenetic forces which cause two types of movement in the
earth viz (i) Horizontal movement and (ii) vertical movement
2. Exogenetic forces – it applies to the processes which
occur at or near the earth’s surface.
3. Folds – Wave – like bands are formed in the crustal rocks due
tangential compressive force resulting from m horizontal movement caused by the
Endogenetic force originating deep within the earth. Such bands are called
folds.
4. Faults - A fault is a fracture in the crustal rocks wherein the
rocks are displaced along a plane called as fault plane.
5. Plate tectonics – the study of whole mechanism of evolution, nature
and motion of plates, deformation within plates and interaction of plate margin
with each other is collectively called as plate tectonics.
6. Volcano – A land form at the end of a conduit or pipe which rises
from the below the crust and vents to the surface. Magma rises and collect in a
magma chamber deep below, resulting in eruptions that are effusive or explosive
forming the mountain/plateau landform.
To understand mountain building
1. Mountain – A general term for any land mass that stands above its
surrounding. In the stricter geological sense, a mountain belt is a highly
deformed part of the earth’s crust that has been injected with igneous
intrusion and the deeper part of which have been metamorphosed. The topography
of Young Mountain is high, but erosion can reduce Old Mountain to flat low
land.
2. Geosyncline – A subsiding part of the lithosphere in which thousands of
metres of sediment accumulate.
To understanding Weathering and Mass movement
1. Weathering – the process of disintegration and decomposition of rocks
in situ, it’s a static process.
2. Mass Movement (mass wasting) – Disintegrated and fragmented rock
materials due to mechanism of weathering process (mechanical, chemical, biotic
and biochemical).
3. Landslide – a general term for relatively rapid types of mass movement
such as debris flows, debris slides, rockslide, and slumps.
4. Slump –It involves intermittent sliding of rock fragments, rock
blocks or soil down slope along a curve plane caused by rotational movement and
displaced blocks (whether rocks blocks or soil blocks) cover very short
distance.
5. Rock slide – its most significant of all types of slides wherein large
rock blocks slide down the hillslope.
6. Creep – very slow and imperceptible movement of materials
(colluviums) is called creep.
To understand erosion
1. Erosion – the processes that loosen sediment and move it from one
place to another on earth’s surface. Agents of erosion include running water,
ice, wind, sea waves , underground water, and gravity.
2. Denudation – A general term that refers to all processes that cause
degradation of the landscape weathering, mass movement, erosion, and transport.
To understand drainage systems
1. Drainage – An integrated system of tributaries and trunk stream,
which collect and funnel surface water to the sea, a lake, or some other body
of water.
2. Stream – long, narrow body of flowing water occupying a stream
channel and moving to lower levels under the force of gravity.
3. Drainage pattern – the drainage pattern means the ‘form’ (geometrical
forms) of the drainage system and the spatial arrangements of streams in a
particular locality or regions.
To understand fluvial landforms
1. Fluvial - Pertaining to river or rivers
2. Fluvial landforms – the landforms either carved out
(due to erosion) or built up (due to deposition) by running water.
3. Surface runoff – The rainwater reaching the earth’s surface becomes
surface runoff when it spreads laterally on the ground surface.
4. Solution or corrosion – It involves the dissolution of
soluble materials through the process of disintegration and decomposition of
carbonate rocks.
5. River meanders – It refers to the bands of longitudinal courses of
the rivers.
6. Ox bow lakes – The lakes formed due to impounding of water in the abandoned
meander loops are called ox bow or horse – shoe lakes.
7. Peneplains – It represents featureless plain having undulating surface
and remnants of convexo – concave residual hills.
8. Delta – the depositional feature of almost triangular shape at the mouth
of river debouching either in a lake or a sea is called delta.
To understand karst landforms
1. Regolith – The blanket of soil and loose rock fragment overlying the
bedrock
2. Groundwater – The water present in the pore spaces of regolith and
bedrocks (those rocks which have not been weathered and eroded) below the
ground surface.
3. Aquifers - A permeable stratum or zone below the earth’s surface
through groundwater moves.
4. Ponores – The vertical pipe – like chasms or passages that connect
the caves and the swallow holes are called ponores.
To understand coastal landforms
1. Swell – The regular pattern of smooth rounded waves that
characterizes the surface of ocean during fair weather.
2. Wavelength – The straight horizontal distance between two successive
crests or through.
3. Swash or uprush – The turbulent water, known as swash or uprush rushes
shoreward with great velocity and force.
4. Plungeline – The distance from the shore where the waves break is called
plungeline, where the depth of seawater and the wave height is approximately
equal.
5. Surf – The turbulent forward moving swash or breaker.
6. Hydraulic action – It refers to the impact of moving
water on coastal rocks.
7. Cliffs - Steep rocky coast rising almost vertically above sea water
is called sea cliff, which is very precipitous, with overhanging creast.
8. Wave cut platform – Rock – cut flat surface in front of
cliffs they are also known as shore platform, which are slightly concave
upward.
9. Beaches – Temporary or short – lived deposits of marine sediment
consisting of sands, shingles, cobbles etc. On the sea shore.
10. Bars – The ridges, embankments or mounds of sand formed by
sedimentation through sea waves parallel to the shore line.
11. Barriers – The larger forms of bars.
To understand arid and
semiarid landforms
1. Ergs – The deserts having mobile sands, Arabic word erg means
shifting sands
2. Attrition – It involves mechanical tear and wear of the particle
suffered by themselves, while they are being transported by wind through the
processes of saltation, and surface creep
3. Saltation – It involves the movement of sand and gravels through the
mechanisms bouncing, jumping and hopping by turbulent air flow.
4. Mushroom rocks – The rocks having broad upper part and narrow base
resembling an umbrella or mushoroom.
5. Inselbergs – These are very controversial landforms , this is a German
word, was used by Passarge in 1904 to
indicate sharply rising residual hill above the flat surfaces in South Africa.
6. Zeugen – Rock masses of tabular form resembling a capped inkpot
standing on softer rock, pedestal shale, mudstone etc.
7. Yardangs – These are steep sided deeply undercut overhanging rock
ridges separated from one another by long groups corridors or passage ways cut
in desert floors relatively softer rocks
8. Loess – It is the example of most significant windblown deposits.
Loess (German term loess meaning there by fine loam, loose or unconsolidated
materials) represents thick deposits of unstratified, non indurated, buff-
coloured, well sorted, fine grained sediments consisting of quartz silt
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