Underground Water and Landforms

Water forms

  • Artesian well
  • water rises automatically under its own pressure to the surface
  • Springs
  • Springs are surface outflow of ground water through an opening in a rock underhydraulic pressure
  • Hot springs
  • Springs with hot water outflow are called hot springs
  • occurs in areas of activity or recent vulcanism
  • Hot springs in India
  • Jammu and Kashmir
  • Himachal Pradesh – Manikaran in Kulu valley, Tatapani near Shimla
  • Jharkhand – Rajgir and Sitakund
  • Uttarakhand – Badrinath
  • Assam
  • Haryana – Sohna

Geysers

  • Springs emitting hot water and steam in forms of fountains or jets at regular intervals are called geysers
  • water is forced out by steam pressure at intervals

Landforms

  • The distinctive topography formed due to the action of underground water in limestone region is known as Karst topography
  • On the surface
  • Sink holes
  • A sinkhole is a funnel-shaped depression in a region of limestone or chalk terrain
  • Swallow holes
  • They are sylindrical in shape lying underneath the sinkholes at some depth
  • surface streams often enter the sinkholes and then disappear underground through swallow holes

Underground

  • Caverns
  • Caverns are interconnected subterranean cavities in bedrock formed by the corrosion of limestone
  • Caverns in India
  • Stalactites
  • Solid conical depositional features hanging from the caver’s roofs are called stalactites
  • They are formed by the evaporation of water containing limestone in solution
  • Stalagmites
  • Broad conical pillars developing on the floor of the caverns are called stalagmites
  • They are formed by the evaporation of water dripped from the stalagmites containing limestone

Wind and Sea wave Landforms

Wind landforms

  1. Erosional landforms
  2. Mushroom Rocks
  3. Wind Eroded Basins
  4. Depositional landforms
  5. Sand Dunes
  6. Barchan
  7. Seif Dunes
  8. Loess
  • A fine-grained unstratified accumulation of clay and silt deposited by the wind

Sea wave landforms

  1. Erogional landforms
  2. Sea Cliff
  • Impact of the sea waves erodes the lower part of coastal rocks more rapidly than the upper part
  • The upper part of the rock projects out towards the sea and fall into the sea under its own weight, leaving a vertical wall called cliff
  1. Sea caves
  • Sea Arches
  1. Sea Stacks
  2. Depositional landforms
  3. Beach
  4. Sand Bar
  • deposits of sand and gravel laid down by waves and currents form an embankment called sandbar
  • Spit
  • one end of sandbar extended into the sea is called a spit
  1. Lagoon
  • ends of sandbar join to enclose a part of the sea water between the coast and the bar forming a lake of saline water called lagoon
  • lagoons are also formed by wave erosion
  • lagoons in India
  • Vembanad lake in Kerala
  • Chilka and Pulicat lakes

Glaciers and landforms

Snowfields

  • Permanently snow covered regions are called snowfields
  • snow accumulates and compacts to form Glaciers
  • Snowfields occur in polar regions and on high mountainous areas
  • Snowfields are always found above the snow line
  • factors affecting snow line are
  • latitude
  • amount of snowfall
  • direction of winds
  • slope of the land

Glaciers

  • great mass of ice moving under its own weight is called a glacier
  • Velocity of glacier is very low and it moves from a few centimetres to a few meters in a day
  • Types of Glaciers
  1. Continental glaciers
  • A thick ice sheet covering vast area land is called a continental glacier
  • found mainly in Antarctica and Greenland
  1. Valley glarier
  • Large mass of ice moving down from the high mountainous regions into valleys is called a valley glacier
  • also called as mountain glacier
  • Glaciers in India
  • The longest glacier in India is the Siachen Glacier in Karakoram range which is 72 km long
  • ganga river originates from Gangotri glarier (25 km long)
  • Yamuna river originates from Yamunotri glacier

Glacial landforms

  1. Erosional landforms
  2. Cirque
  • bowl shaped depression at the head of a valley or on a mountainside, formed by glacial erosion
  1. U-shaped valley
  • valley formed in a manner resembling the shape U is called U-shaped valley
  • These valley are relatively straight with flat floor and nearly vertical sides
  • Hanging valley
  • valley of the tributary glacier hanging downwards at the point of its confluence with the main valley is called a hanging valley
  1. Depositional landforms
  • Deposits of glaciers are called as moraines
  1. Terminal moraine
  • Glacier deposits at the end of the valley glacier in the form of a ridge is called terminal moraine
  1. Lateral moraine
  • Deposits on either side of a glacier is called lateral moraine
  • Medial moraine
  • Moraines formed on the confluence of two glaciers are called medial moraines
  1. Ground moraine
  • Deposits left behind in areas once covered by glaciers are called ground marines

 

Ocean Basins and Submarine Relief

Ocean Basins

  1. Continental shelf
  • The shallow submerged extension of continent is called the continental shelf
  • The width of the continental shelf ranges between a few kilometres to more than 100 km
  • Formation of continental shelf
  1. erosional deposits of ocean
  2. deposits of rivers
  • retraction of ice sheets
  • Largest continental shelf : Siberian shelf in the Arctic ocean(1500 km)
  • economic importance
  • Abundant in fishes
  • Minerals such as sand and gravel
  • petroleum and natural gas
  1. Continental slope
  • The steep descent of the seabed from the continental shelf to the abyssal zone
  • Inclination of continental slope is around 5 degrees
  • Sedimentary deposits on the continental slope gives rise to formation of continental rise
  1. Continental rise
  • Connects the continental slope with the Abyssal plains
  • it represents the final stage in the boundary between continents and the deepest part of the ocean
  1. Abyssal plains
  • Abyssal plains are extremely flat and featureless plains of the deep ocean floor
  • Abyssal plains cover major portion of ocean floor between the depth of 3000 m to 6000 m
  • It is major reservoir of biodiversity
  1. Ocean deeps or trenches
  • These areas are the deepest parts of the oceans
  • They occur at the bases of continental slopes and along island arcs
  • they are significant in the study of plate tectonics
  • Pacific ocean has maximum number of trenches
  • Deepest trench
  • Mariana trench
  • Location : West pacific ocean
  • Deepest point : Challenger deep
  • Steepest trench
  • Tonga trench
  • Location : South pacific ocean
  • Deepest point : Horizon deep

Submarine relief

  1. Mid-Oceanic Ridges
  • Mountain systems beneath the ocean water are known a submarine ridges
  • They are linear belts occurring near the middle of the oceans and are also called mid-oceanic ridges
  • These ridges are interested by faults
  • Earthquakes and Volcanic eruptions occur frequently in mid-oceanic ridges
  1. Seamount
  • Submerged Volcanoes with sharp tops called seamunts
  • g. Hawai and Tahiti Islands
  1. Guyots
  • A flat topped seamount or in active volcano flattened by erosion and covered by water is called Guyot
  1. Submarine Canyons
  • Submarine canyons are deep valleys cut across the continental shelves and slopes
  • g. Gogavari canyon, Hudson canyon
  1. Atoll
  • These are low islands found in the tropical oceans consisting of coral reefs surrounding a central depression

Ocean Salinity

Basics

  • Salinity is the measure of total content of dissolved salts in sea water
  • Salinity is calculated in grams per kg and expressed as parts per thousand(ppt)
  • Sea water with salinity of 24.7% is demarcated as brackish water

Factors affecting ocean salinity

  1. Evaporation
  2. Precipitation
  • Outflow of rivers
  1. Freezing and thawing of ice
  2. Wind
  3. Ocean currents
  • Temperature
  • Density

Distribution of salinity

  • Salinity in open ocean ranges between 33% and 37%
  • Salinity in landlocked sea is as high as 41%
  • Average salinity of northern hemisphere is higher than southern hemisphere
  • The highest salinity is recorded between 150 and 200 latitudes
  • The average salinity of the Indian Ocean is 35%
  • Salinity increases with depth and there is a distinct zone called the halocline
  • High salinity seawater sinks below the lower salinity water, which leads to stratification of ocean waters
  • Arabian Sea shows higher salinity due to high evaporation and low influx of fresh water
  • The north sea records higher salinity due to more saline water brought by the North Atlantic Drift
  • Baltic Sea and Black sea records low salinity due to influx or river waters in large quantity

Ocean Temperature

Factors Affecting Temperature Distribution

  1. Latitude
  • The temperature of surface water decrease gradually from the equator towards the poles
  • The mean annual temperatures in tropical seas (270 C) is higher than poles(1.80 C)
  1. Unequal distribution of land and water
  • the oceans in the northern hemisphere receive more heat than southern hemisphere
  • This is due to the larger extent of land in northern hemisphere than southern hemisphere
  • Prevailing wind
  • winds blowing from the land towards the oceans drive warn surface water away from the coast
  • This results in the upwelling of cold water from below an longitudinal variation in temperature
  1. Ocean Currents
  • warn ocean currents raise the temperature in cold areas while the cold currents decrease the temperature in warm ocean areas
  • g. Gulfstream(warm) Labrador current (cold current)

Facts

  • The process of heating and cooling of the oceanic water is slower than land
  • The maximum temperature of the oceans is always at their surfaces
  • Enclosed seas
  • in the low latitudes record relatively higher temperature than the open seas
  • in the high latitudes have lower temperature than the open seas
  • The highest temperature is not recorded at the equator but slightly towards north of it.
  • The temperature falls very rapidly up to the depth of 200 m and decreases gradually thereafter
  • Region below the sea surface from where, there is a rapid decrease in temperature is called thermocline
  • The average temperature is
  • 220 C at 200 C latitudes
  • 140 C at 400 latitudes
  • 00 C near poles

 

Tides

Basics

  • Tides are periodic rise and fall of the sea level due to the attraction of the moon and sun
  • Tides are generated by the gravitational force between earth, sun and moon

Tides

  • Flood tide
  • The incoming tide towards the land is called flood tide or high tide
  • Flood tide is a high tide
  • Ebb tide
  • tide going out or withdrawn, is an ebb tide
  • ebb tide is a low tide

Types of Tides

  1. Spring tide
  • Generated, when the sun and the moon are in a straight line as on a new moon or a full moon day
  • Combined force of the sun and the moon pulling together at the same time in the same direction produces spring tide
  1. Neap tide
  • During the first quarter and the third quarter, the gravitational force of the sun and the moon is at right angle
  • At this time, the two pulls are opposing each other and cancel or neutralize each other’s forces producing a weak tide called as neap tide

Factors affecting the size the tides

  1. Location of the sun, the moon and the earth in relation to each other
  2. Variation of distances between the sun and the moon from the earth

Advantages of tides

  1. Tidal power
  2. Increased fish catch during the new and full moon days
  3. Desiltation of river mouths
  4. Increased impetus to the ships at tidal bores

Facts

  • Moon exerts twice the gravitational pull of the sun on the earth
  • coastal areas experience two high tides and two low tides per day
  • Enclosed water bodies experience only one high tide and one low tide per day called as diurnal tides
  • Regular interval between two high tides or between two low tides is 12 hours and 25 minutes
  • Each day the high tide arrives about 51 minutes later than on the previous day due to delayed rising and setting of the moon by 51 minutes
  • Gravitational attraction of the moon is more effective on the earth than the gravitational attraction of the sun
  • Highest spring tide occurs when the moon is closest to the earth

Ocean Currents

Facts

  • The steady flow of ocean water in a prevailing direction over great distances
  • The average speed of current is between 3.2 km to 10 km per hour
  • Ocean currents
  • with higher speed are called stream
  • with lower speed are called drift

Types of ocean current

  • Warm currents
  • Warm currents flow equatorial regions towards poles
  • They have higher surface temperature
  • Cold currents
  • Cold currents flow from polar regions towards equator
  • They have lower surface temperature

Origin and circulation

  1. Change in density
  • Temperature
  • Sea water’s density varies with temperature
  • The higher the temperature of water, the lesser will be the density
  • Warm and less dense waters of the equator moves towards the poles
  • Cold and high dense waters of the poles move towards the equator
  • Salinity
  • Higher salinity increases the density of the water and the water sinks
  • Water with higher salinity flows towards the less dense water.
  1. Rotation of the Earth
  • Ocean water is affected by Coriolis force and follows the Ferrel’s Law
  • Ocean currents follow
  • clockwise direction in the northern hemisphere
  • anti-clockwise direction in the southern hemisphere
  • Direction of planetary Winds
  • Ocean currents change their direction according to the change in the direction of winds in the latitude
  • Ocean currents follow the direction of planetary winds such as easterlies, westerlies etc.

 

Currents of Atlantic Ocean

Atlantic Circuit

  • Labrador current (cold current)
  • South equatorial current (warm current)
  • Joins north equatorial current – Florida current – Gulf stream – North Atlantic drift –
  • West wind drift (cold current)
  • Benguela Current
  • Falkland Current
  • East Greenland Current (cold Current)

Significance of Atlantic Currents

  • Warm Currents
  • Gulf stream
  • Florida current
  • North Atlantic drift
  • Norwegian current
  • Canary current
  • Guinea current
  • Cold currents
  • East Greenland current
  • Labrador current
  • Falkland current
  • Benguela current

Composition of Atmosphere

  1. Gases

Atmosphere consist a mixture of different types of gases

  • Composition
  • Nitrogen – 78.08%
  • Oxygen – 20.95%
  • Argon – 0.93%
  • Carbon dioxide – o.036%
  • Helium – 0.0005%
  • Neon – 0.002%
  • xenon – 0.-00009%
  • Hydrogen – 0.00005%
  • Nitrogen and Oxygen together makeup 99% of the gases of atmosphere
  • 99% of the total mass of the atmosphere is confined to the height of 32 km from the earth’s surface
  • ozone
  • It is limited to the ozone layer found between 10 and 50 km above the earth’s surface
  • acts as a filter and absorbs the ultra-violet rays radiating from the sun
  1. Water vapour

Gaseous form of water present in the atmosphere is called water vapour

  • Water vapour is the source of all kinds of precipitation
  • water vapour formation
  • Evaporation
  • oceans
  • seas
  • rivers
  • ponds
  • lakes
  • Transpiration
  • plants
  • trees
  • living beings
  • Concentration
  • Its maximum amount in the atmosphere could be up to 4 present
  • Maximum amount of water vapour is found in hot-wet regions
  • Least amount is found in the dry regions
  • Significance
  • It absorbs part of insolation from the sun and preserves the earth’s radiated heat
  • it acts like a blanket allowing the earth neither to become too cold nor too hot
  1. Dust particles
  • found in the lower layers of the atmosphere
  • dust particles help in the condensation of water vapour to form droplets by sticking around these dust particles

Layers of Atmosphere

Basics

  • Atmosphere is divided in to five layers based on their temperature and density
  • 97% of the atmosphere is limited to the height of 30 km
  1. Troposphere
  • Lowest layer of the atmosphere
  • extends about 18 km on the equator and 8 km on the poles
  • The troposphere contains roughly 80% of the mass of Earth’s atmosphere
  • Depth of troposphere is maximum at equator than poles due to
  1. hot convection currents over the equator
  2. less dense air at the equator
  3. larger gravitational pull over the air at the poles than the equator
  4. larger centrifugal force at the equator
  • All kinds of weather changes takes place within this layer
  • Temperature decreases gradually with increase in altitude
  • The average rate of temperature change is about 6.5 C per 1000 metres
  • Only layer that can be accessed by propeller-driven aircraft
  1. Stratosphere
  • Extends about 50 km from the earth surface
  • It is called as stratosphere due to its stratification into warm upper layers and cold lower layers
  • Ozone layer lies within the stratosphere
  • 90% of the ozone in Earth’s atmosphere is contained
  • Temperature
  1. remains constant up to the height of 20 km
  2. after 20 km, it increases gradually with increase in the height

this rise in temperature is caused by the absorption of ultraviolet radiation (UV) radiation from the Sun by the Ozone

  • The air blows horizontally without much turbulence and is ideal flying of aircrafts
  • highest layer that can be accessed by jet-powered aircraft
  1. Mesosphere
  • Extends up to 30 km from stratosphere
  • Temperature goes on decreasing with increase in altitude
  • It is the coldest place on Earth and has an average temperature around – 85 C
  • Meteors fall and burn in this layer
  • It is too high above Earth to be accessible to aircraft and balloons, and too low to permit orbital spacecraft
  1. Thermosphere
  • Extends up to the height of 400 km from the surface of the earth
  • This layer is completely cloudless and free of water vapour
  • Temperature starts increasing again with increasing height in this layer
  • Temperature inversion in the thermosphere occurs due to the extremely low density of its molecules
  • Lower part of the thermosphere from 80 to 550 km above Earth’s surface, contains the ionosphere
  • Electrically charged currents flows in the air in this sphere and hence called as Ionosphere
  • Radio waves are reflected back on the earth from this sphere
  • aurora borealis and aurora australis are occasionally seen in the thermosphere
  • formed due to the ionisation of atmosphere by solar radiation
  • ionization in the mesosphere largely ceases during the night
  • International Space Station orbits in this layer, between 320 and 380 km
  1. Exosphere
  • last layer of the atmosphere located above ionosphere
  • extends beyond 400 km above the earth
  • Density of air is very sparse in the exosphere
  • mainly composed of extremely low densities of hydrogen, helium and heavier molecules of nitrogen, oxygen and CO2
  • Exosphere doesn’t behave like a gas, and the particles constantly escape into space
  • aurora borealis and aurora australis sometimes occur in the lower part of the exosphere
  • exosphere contains most of the satellites orbiting earth

 

Insolation

Facts

  • Incoming solar radiation through short waves is turned as insolation
  • Amount of insolation received on the earth’s surface is far less due to
  • small size of the earth
  • distance from the sun
  • Water vapour, dust particles, ozone and other gases present in the atmosphere absorb a small amount of insolation
  • amount of insolation received on the earth’s surface is not uniform, it varies from place to place to place and form time to time

Distribution of Insolation

  • Tropics receive the maximum annual insolation
  • Insolation is more in summer than winter

Factors influencing Insolation

  1. The angle of incidence
  • when the sun is almost overhead, the rays of the sun are vertical, giving more amount of insolation at that place
  • When sun’s rays are oblique angle of incidence is small, resulting in less amount of insolation
  1. Duration of the day
  • The longer the duration of the day, the greater is the amount of insolation and vice versa
  • Transparency of the atmosphere

 

  • Cloud cover and dust particles, reflects the insolation
  • Water vapour absorbs the insolation
  1. Rotation of earth on its axis
  • Inclination of earth(661/2 degrees) varies the amount of insolation received on various latitudes

Heating and cooling of the Atmosphere

  1. Radiation
  • Major amount of heat energy coming to and leaving the earth is in the form of radiation
  • Long wave terrestrial radiation heats up the atmosphere more than the incoming short wave solar radiation
  1. Conduction
  • conduction takes place when two bodies of unequal temperature are in direct contact with one another
  • Convection
  • vertical heating of the atmosphere is known as convection
  • Heated air in the surface rises vertically in the form of currents and transmits the heat to the atmosphere
  1. Advection
  • The transfer of heat through horizontal movement of winds is called advection
  • Local winds such as “Loo” is caused by advection

Terrestrial Radiation

  • Earth gets heated by receiving short wave energy and radiates the energy back to the atmosphere in long wave form
  • Portion of long wave radiation is absorbed by carbon dioxide and the other green house gases and reflected back to the earth
  • This contributes indirectly to the addition of energy to the atmosphere

Remaining energy is reflected back to space thereby maintaining the optimal temperature of earth