Physical Geography Test 1
Weathering Process and Causes
WEATHERING,
PROCESSES AND AGENTS SIMPLIFIED
Weathering
is the physical disintegration of the earth material and change in its chemical
properties due to the action of Air, Water and Organisms at a particular place
without distant removal of its products. It is a continuously occurring process
both on exposed surface of earth and beneath the ground within the rock strata.
Various weathering agents are classified into two major classes.
WEATHERING
PROCESSES OR TYPES
MECHANICAL WEATHERING
It
is also called physical weathering. The process of weathering that occur due to
imposition of certain stresses occurring by some physical means such as
freezing and thawing, expansion of salt crystals, rainfall and temperature.
FACTORS RESPONSIBLE FOR MECHANICAL WEATHERING
Following
factors are responsible
Frost Action
Ice
has a great damaging capacity as the volume of water increases by 9% upon ice
formation. So upon freezing the water in the cracks, joints or pores in the
rocks expand by 9%, as a result the material on both sides of the cracks
experiences huge pressure resulting in the wear and tear of those rocks
Salt Wedging
In
deserts salt play same role as ice. The saline water in small pores and cracks
evaporates leaving behind the deposits of salt crystals that result in cracks
in the rocks. When this process is helped by wind the weathering may occur
Temperature Changes
The
rocks are made up of different mineral grains that have different physical and
chemical properties and different expansion rates on basis of temperature
changes. If continuous temperature changes occur borders between these mineral
grains may be loosened resulting in weathering of rocks.
Rainfall
When
the rain water drops on temperature heated rocks in dry areas, the rocks
develop cracks and are broken
Removal of Overburden
Many
rocks are formed under pressure below the earth crust. When the upper material
is eroded off those underlying rocks are exposed and the pressure is released.
As a result the cracks may occur in these rocks and result in weathering.
Gravity
Many
rocks having large cracks may be disintegrated on the basis of gravity. However
its effect is minute and time taking.
CHEMICAL WEATHERING
The
rocks are made up of mineral particles so the disintegration of these mineral particles
due to chemical action results in the breakdown of the whole rock. This type of
weathering is called Chemical Weathering. Various agents or processes of
chemical weathering are:
Hydrolysis
We
know that hydrolysis is breakdown of material due to water acting as a chemical
agent. When the water present in the rock material comes in contact with
certain minerals of the rock hydrolysis is initiated and during this process
expansion of the rocks occur due to the formation of certain new products. As a
result cracks appear in the rocks and ultimately wear and tear of rocks occur
Oxidation
Chemical
reaction of Oxygen present in the air with any element is called Oxidation. It
is a dominant weathering agent in the tropics. Oxidation process is easy to
judge because when oxygen chemically react with rock minerals it produces Iron
or Aluminum product that show a distinct red color e.g. “Grand Canon”.
Carbonation
Under
various conditions the H2O might be converted into a mild acid solution and its
effectiveness as a weathering agent is increased. For instance when water
combines with CO2 it forms a highly reactive acid known as Carbonic acid. It
reacts readily with Limestone and Dolomite and result in weathering of rocks.
This process is known as Carbonation. It is a prominent process in the humid
areas.
Solution
Some
minerals such as Rock Salt and Gypsum may be Dissolved by water and then
removed in solution resulting in weathering of rocks.
BIOLOGICAL WEATHERING
The
disintegration of rock minerals through the biological agents is known as
biological weathering. For instance Earthworms and plant roots are important in
the development of the soils; Lichens contribute to the breakdown of rocks and
human also play various roles in the disintegration of rocks. It may be
classified as:
Weathering by Animals and Human
An
important aspect of this type is the mixing of soil by the burrowing animals
and the earth worms, Rats, Rabbits and Termites etc. they burrow the soil for
food and shelter and thus soften it and cause its weathering. Similarly hoved
animals or grazers also soften the upper layer of soil with their hoves and
make it soft. Human also contribute a lot to the weathering process through
activities like mining, roads, dams, tunnels and other construction processes.
The harmful chemicals released by industry and Auto-mobiles also act as
weathering agents.
Weathering due to Vegetation
The
trees and shrubs grow in a thin layer of fertile soil on the Rocks and
mountains. Their roots may percolate deep into the rocks and on growth these
produce cracks in the rocks causing the weathering of the rocks. Similarly
Lichens (combination of Algae and Fungi) living on bare rocks by drawing minerals
from the rock material trough ion exchange method. The swelling and contraction
of lichens as they alternatively get wet and dry may cause small particles of
rock to fall off.
FACTORS AFFECTING WEATHERING
PROCESS
· Nature of rock is an important factor,
if rock is soft it will weather easily and if it is hard process will be slow
· If slope is less there will be less
weathering as compared to sharp slopes
· The rocks with joints are easily
weathered by factors such as temperature variation, Gravity etc.
· Vegetative cover protects rocks. Those
without vegetative cover or having less vegetative cover are more exposed to
weathering process
· Climate is an important factor, humid
climates promote Chemical Weathering whereas dry climate promote Mechanical
Weathering.
IMPORTANCE
OF WEATHERING
It is a significant process in a
way that
· New land forms are produced as a result
of Weathering
· Weathering produces sediments that are
then transported by transporting agent such as Wind and then come under
pressure and converted into Sedimentary Rocks
· Weathered minerals are when transported
to Agricultural zones through agents such as River floods they increase the
fertility of the soils.
Ocean Currents of Indian Ocean
OCEAN CURRENTS
OF INDIAN OCEAN
CURRNTS OF NORTH
INDIAN OCEAN
The
currents of North Indian Ocean are influenced by the seasonal impact of Monsoon
winds.
South-West
Monsoon Drift (SWMD)
In
the winter season this Current starts from the eastern coasts of Africa under
the influence of monsoon winds and moves along Arabian Peninsula then the
Persian Gulf, the Bay of Bengal and finally disappears in the strait of Melaka.
North-East
Monsoon Drift (NEMD)
During
the summer season the Current originates from the strait of Melaka and after Bay
of Bengal, Persian Gulf and the Arabian Peninsula it reaches the eastern coasts
of Africa and disappears.
CURRENTS OF
SOUTH INDIAN OCEAN
South Equatorial
Current (SEC)
This
Current starts from the western coasts of Indonesia and moves towards coasts of
eastern Africa. It is then deflected towards South and reaches Madagascar
Islands.
Mozambique
Current (MC)
On
striking the Northern borders of Madagascar the South Equatorial Current is
deflected into two branches. One moving along western coasts of Madagascar and
eastern coasts of Mozambique is known as the Mozambique Current.
Madagascar
Current (MC)
The
other branch of South Equatorial Current that moves along the eastern coasts of
Madagascar is known as the Madagascar Current.
Agulhas Current (AC)
When
the waters of Madagascar Current and Mozambique Current reunite and move
further along eastern coasts of Africa the new Current is formed known as
Agulhas Current.
West Wind Drift (WWD)
As
it reaches the borders of eastern coasts of South Africa the Agulhas Current
comes under the influence of strong winds and is deflected towards east as West
Wind Drift.
West Australian
Current (WAC)
On
reaching the Australian western borders this Current comes under influence of
strong winds again and is deflected North wards this time. It is now called
West Australian Current and ultimately joins South Equatorial Current to
complete the Circuit.
Ocean Currents of Pacific Ocean
OCEAN CURRENTS
OF PACIFIC OCEAN
CURRENTS OF
NORTH PACIFIC OCEAN
North Equatorial
Current (NEC)
It
starts from the Western borders of South America and reaches the borders of
Philippines.
Kurushio
Current/ Japan Current (JC)
When
the North Equatorial Current reaches the Philippines Islands it is deflected
towards North and washes the Islands of Japan and is known as Kurushio or Japan
Current.
North Pacific
Current (NPC)
After
crossing Japan the Japan Current comes under the influence of strong winds and
is deflected towards east and moves towards the western borders of North
America as North Pacific Current where it is deflected in two directions.
California
Current (CC)
One
part of North Pacific Current is deflected towards south and comes in contact
with the state of California so named as California Current and ultimately
joins North Equatorial Current to complete the circle.
Alaska Current (AC)
The
second branch of North Equatorial Current moves towards north along the coasts
of North America passing along the borders of Alaska, ultimately falling into
Arctic Ocean known as Alaska Current.
Kamchatka
Current (Oyashio) (KC)
This
Current originates from Arctic Ocean and after crossing the Sea of Bering it
joins North Pacific Current. It is a cold Current.
Okhotsk Current (OC)
This
Current comes from the Sea of Okhotsk which is situated in the south-eastern
borders of Russia and ultimately becomes the part of Japan Current. It is also
a cold Current.
CURRENTS OF
SOUTH PASIFIC OCEAN
South Equatorial
Current (SEC)
This
Current originates from western borders of Latin America and moves parallel to
the equator and reaches the eastern borders of Australia.
East Australian
Current (EAC)
When
the South Equatorial Current strikes the north-eastern borders of Australia it
is deflected towards south and washes the whole coast of east Australia. It is
called the East Australian Current.
South Pacific
Current (SPC)
When
the East Australian current reaches the east-southern borders of Australia it
comes under the influence of strong winds and adopts the path towards east and
moves towards western borders of Latin America. Now it is called South Pacific
Current.
Humboldt Current (HC)
It
is a cold Current that originates from the north of Antarctica and passes along
the coasts of western Chile and ultimately joins the South Pacific Current
Ocean Current of Atlantic Ocean
OCEAN CURRENTS
OF ATLANTIC OCEAN
CURRENTS OF NORTH ATLANTIC OCEAN
North Equatorial Current (NEC)
It
starts from western coast of Africa and moves towards the eastern coasts of
Latin America parallel to the Equator.
Antilles Current (AC)
It
gets its name from the islands of Antilles. As the North Equatorial Current
strikes the coasts of Brazil near “Cape de Sea Rogue” it is deflected towards
north and when it reaches West-Indies it splits into two branches. The one that
passes along the eastern coast of West-Indies is called Antilles Current.
Florida Current (FC)
Both
Antilles Current and NEC reach the gulf of Mexico where the waters of two large
North American rivers “Mississippi” and “Missouri” also fall. Here a rise in
water level occur that result in generation of Florida Current that moves along
the USA coasts in the east up to “Cape Halteras”
The Gulf Stream (GS)
The
Current of Ocean that is moving from “Cape Halteras” to “Grand banks” is Known
as the Gulf Stream.
North Atlantic
Drift (NAD)
As
the current reaches the “Grand Banks” the effect of Westerlies changes
direction of the Current towards east and it moves towards Europe in form of
North Atlantic Drift.
Norwegian
Current (NC)
When
NAD reaches Ireland coasts it divides into two branches. One moves along the
coasts of Norway as Norwegian Current ultimately it enter Arctic Ocean.
Canaries Current (CC)
The
other branch of North Atlantic Drift moves towards Equator along the coasts of Canary
so is called Canaries Current. Finally this cool current joins the North
Equatorial Current and completes its circuit.
East Greenland
Current (EGC)
It
is a cool current that moves between Greenland and Iceland and enters the North
Atlantic Drift. The point of convergence is near Iceland where dense fog is
produced as a result. This current also cools down North Atlantic Drift.
Labrador Current (LC)
This
current moves from Arctic to Atlantic in North to South Direction along the
eastern coasts of Canada and meets Warm Gulf Stream at New-Foundland. As a
result dense fog is produced here as well.
Saragossa Sea
It
is the calm part of North Atlantic Ocean within the close circuit of North
Equatorial Current, Gulf Stream, North Atlantic Drift and Canaries Current. It covers
almost 11000 Km2 of area. It is named so because Saragassum grass grows over
its surface due to its static nature.
CURRENTS OF SOUTH ATLANTIC OCEAN
South Equatorial
Current (SEC)
This
current originates from the western borders of continent of Africa and moves
parallel to the equator and reaches the eastern coasts of Brazil
Brazilian
Current (BC)
On
striking the Brazilian coasts the South Equatorial Current is deflected towards
the south along Brazilian coasts and is known as Brazilian Current
South Atlantic
Drift (SAD)
When
the Brazilian Current reaches the Falkland Islands it comes under the influence
of strong Westerlies and is deflected towards east and is known as South
Atlantic Drift.
Falkland Current (FC)
This
is a cold Current that starts from the southern part of Ocean near the coasts
of Antarctica and washes the borders of Falkland Island near eastern coasts of
Argentina. It falls in Brazilian current and adds cooling effect in it.
Benguela Current (BC)
When
the South Atlantic Drift strikes the Western Coasts of Africa its direction is
changed towards north and touches the coasts of Benguela and is known as
Benguela Current. It ultimately joins the South Equatorial Current.
Ocean Currents
OCEAN CURRENTS,
THEIR CAUSES AND EFFECTS SIMPLIFIED.
“Ocean
currents are the general movements of water in the ocean in a fairly defined
direction”
These
ocean currents produced due to the movement of the water not only affect the
71% water portion of earth but also the continental landmasses. Hence their study
is vital for understanding the weather and climate of each part of the Planet.
Like
atmospheric circulation above it the movement of ocean is also responsible for
transfer of heat from tropics to poles.13% of heat from low to high latitude and
25% of heat from tropics to poles is transferred through ocean currents. It is
through the movement of water in large currents that ocean play vital role in
the constant adjusting the heat Imbalance of earth’s surface. The currents may
b horizontal, vertical or diagonal but all the heat carrying activity takes
place in the uppermost 100m (330ft) of water of horizontal currents.
It
is very difficult to distinguish the currents from their surrounding as they
more slowly and steadily, averaging only about 8km/hr. That is why these are
also called (Drifts) as they slowly move in the same direction in which winds
blow the fast moving currents are only observed where narrow straits are
located e.g. between Florida and Cuba.
TYPES OF
CURRENTS
WARM
CURRENTS
The
Currents that move from hotter region towards cold regions.
Examples
North
Equatorial Currents
South
Equatorial Currents
East
Australian Current
COLD CURRENTS
The
Currents that move from cold region towards hotter region.
Examples
East
Greenland Current
Falkland
Current
Kamchatka
Current
CAUSES, ORIGIN
AND GENERATION OF OCEAN CURRENTS
The
ocean currents are produced in several ways
PREVAILING WINDS
The
blowing winds provide the kinetic energy to the water that enables it to drift
in the direction of the winds.
EVAPORATION
High
rate of evaporation causes lowering of water level due to the escape of water
molecules, as a result the water from surrounding areas of low evaporation move
towards the areas of higher evaporation. For instance the Mediterranean Sea has
higher evaporation rate as compared to the Atlantic Ocean, so the current moves
from Atlantic Ocean towards Mediterranean Sea to compensate evaporation losses.
DIFFERENCE OF
TEMPERATURE
It
is property of water that it becomes dense as temperature decreases and the
density is maximum at 4⁰C. Due to
increase in the density the water becomes heavier and settles down that result
in a net influx of water from tropics towards poles is created in the form of
water Current.
SALINITY
DIFFERENCE
The
increase in salinity result in the increase of water density, hence the water
of more saline oceans settle down and the water from surrounding less saline
areas move towards it in form of water Current.
ROTATION OF THE
EARTH
The
earth is constantly rotating around its axis as a result Coridis Force is
produced. This force acts on the water bodies and moves them in specific directions.
A good example of this effect is the Zigzag path of the rivers under influence
of these forces.
SHAPE OF THE COASTS
The
coastal shapes not only change the direction of the currents but also have the
ability to generate the currents. The shape of the coast may be such that the
water is piled up producing a slightly higher sea level as compared to the
surrounding Ocean. As a result Ocean Current may be generated. It is due to the
shape of the coast that the North Equatorial Current is diverted towards
North-East on reaching gulf of Mexico and comes out as Gulf Stream.
CHANGE OF
SEASONS
Sometimes
the change in seasons acts as driving force for current generation. A good
example is in North Indian Ocean. Here South-West Monsoon Drift and North-East
Monsoon drift are the currents that are governed by Monsoon winds that move
from East to West in Summer and from West to East in the winter season.
EFFECTS OF THE
OCEAN CURRENTS
EFFECT ON
CLIMATE
The
currents influence the Temperature, Rainfall and many other Climatic elements
of a particular area.
TEMPERATURE
When
we look at the Map, New-Foundland and United Kingdom are almost on the same
Latitude but New-Foundland remain frozen for almost 9 months due to the cold
Labrador Current flowing near it whereas ports of United Kingdom are open
almost the whole year.
RAINFALL
The
winds that flow over the warm currents have the ability to carry large amount
of water so they cause heavy rainfall on condensation. The winds that blow over
the cold currents do not have this ability so they don’t produce rainfall. It
is interesting to note that most of the hot deserts have cold currents in their
neighborhood. For instance Canaries Current flow along the Sahara Desert and
the Bengulla Current along the Kalahari Desert.
FOG
Thick
fogs are produced at the meeting points of the cold and warm Ocean Currents
e.g. at New-Foundland thick fog occurs due to the meeting of warm Gulf Stream
and cold Labradore Current.
EFFECT ON TRADE
EFFECT ON
AVAILIBILITY OF COASTS
The
coasts along the warm Currents are open almost throughout the year e.g. Ports
of North-west Europe are open whole year due to warm Gulf Stream whereas most
of the parts of eastern borders of North America remain closed for nine months
due to cold Currents.
DANGER TO SHIPS
Cold
currents flowing from poles bring large icebergs that cause accidents. The
point where two currents meet produce fog resulting in accidents.
EFFECT ON MARINE
ORGANISMS
Cold currents bring large quantity of
planktons and provide food for the fish and also serve as good fishing grounds.
Good quality of fish floats to the coasts along the currents. Currents sweep
large quantity of refuge off the coast that serve as food for planktons. Fishing
grounds are produced at meeting points of cold and warm currents.
Rock Cycle Simplified
THE ROCK CYCLE
The earth is
constantly changing and this happens in a cyclic manner known as the Rock
cycle. This continuous process has neither a start nor an ending. High
temperature and pressure deep inside the crust melts the crustal rocks. As a
result the magma rises and it either intrudes into existing rock material or
extrudes out of earth surface in the form of lava producing both Igneous and
Metamorphic Rocks. The exposed rocks are affected by weathering and erosion.
Then deposition of this eroded material produces sedimentary rocks. The crustal
force pushes Sedimentary, Igneous and Metamorphic rocks deep in the crust and
if they reach lowest levels in the crust will be melted again and a new cycle
will begin again and will continue in this manner.
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