VisionIAS - Video Classroom Lecture

Geography Class 02

REVISION OF THE LAST CLASS (05:31 PM)

Marine Erosional Landforms

CLIFFS AND WAVE-CUT PLATFORMS (05:36 PM)

The sea attacks the base of the cliff forming a wave-cut notch.
The notch increases in size causing the cliff to collapse.
The backwash carries the rubble towards the sea forming a wave-cut platform.
The process repeats and the cliff continues to retreat.

FORMATION OF CLIFFS & WAVE-CUT PLATFORMS – GoLearnGeography

MARINE DEPOSITIONAL LANDFORMS (05:53 PM)

When the wind blows parallel to the coastline, the wave performs longshore drift, meaning that the wave travels parallel to the coastline.
The longshore drift results in the formation of depositional features like:
Spits:
Longshore drift moves material along the coastline.
It is a long narrow ridge of sand or pebble with one end connected to the coastline and the other end running into the sea.
Over time, spit grows and develops as a hook.
Waves can not get past a spit, which creates a sheltered area where silt is deposited and salt marshes form.
Bars:
It is a stretch of sand deposition off the shoreline in a parallel direction.
Exampple- Chilika Lake
Tombolo:
It is a ridge of sand and shingle joining the mainland to an island.

KARST LANDFORMS (06:21 PM)

There are two types of Karst Landforms:
Erosional:
All the erosional landforms are formed due to the process of solution.
Sinkholes:
The most recognisable karst landform is the sinkhole.
This is a bowl, funnel or cylindrical-shaped depression in the earth which feeds water underground.
Doline:
A sinkhole with a diameter of around 1 km.
Uvala:
When two or more doline coalesce to form a large sinkhole is called Uvala.
Polje:
These are major sinkholes with flat floors and steep walls.
Limestone Pavement:
These are small solution pits, grooves or runnels, collectively called pavements or Karren.
Karst Caves
Depositional:
Stalactite/Stalagmite:
These are elongated forms of various minerals deposited from the solution by slowly dripping water.
A stalactite hangs like an icicle (a pendent mass of ice formed by freezing or dripping water) from the ceiling of a cavern.
A stalagmite appears like an inverted stalactite, rising from the floor of a cavern.
Cave Pillars

CLIMATOLOGY (06:59 PM)

The climate is defined as the study of weather conditions over a large time, normally per 30 years.
Weather is defined as day-to-day changes in temperature, pressure, humidity, winds, cloud cover and precipitation.
These are called weather parameters.
All these weather parameters play their role in the medium called atmosphere.
Atmosphere: (07:35 PM)
It is a thin layer of gases enveloping the earth's surface and the gases are held to it due to gravity.
Composition:
The atmosphere consists of normally two gases: Nitrogen (78%) and Oxygen (21%).
Argon occupies 0.9% and Carbon dioxide occupies 0.03%.
The remaining gases in the atmosphere are called trace gases.
Structure:
Just like the Earth's interior, the atmosphere of the Earth is also a layered structure.
The first layer is called as Troposphere in which humans and other life forms are living.
Troposphere:
'Tropous' in the Latin language means mixing.
Because of the mixing of the gases, the Troposphere is a turbulent layer.
The turbulence is like rainfall/cyclones/lightning and thundering.
These weather disturbances are due to the presence of 75% of the mass of the atmosphere.
99% of the moisture and 90% of the clouds are found in the troposphere.
The troposphere is an unevenly distributed layer.
It is more over the equator and less over the poles.
It extends up to 18 kilometers over the equator and it is just 8 kilometers over the poles.
This is due to equatorial areas experiencing high temperatures and the gases becoming light in density and rising vertically up to 18 kilometres.
In the polar region, the temperatures are very low and the gases are restricted only up to 8 kilometres.
The other minor reason for this unequal distribution is the gravitational pull of the earth.
The gravitational pull of the earth is not equally distributed.
It is strong over the poles and weak over the equator.
Lapse Rate: (08:05 PM)
A change in temperature for height is called lapse rate.
Positive Lapse Rate:
A decrease in temperature with an increase in height is called a positive lapse rate.
Normal Lapse Rate:
If there is a uniform decrease in temperature with an increase in height, it is termed a normal lapse rate.
It is for every 165 meters of ascent, 1 degree of temperature decreases.
For every 1000 meters, 6.5 degrees of temperature decreases.
Tropopause:
Between 6 to 8 km over the poles and 16 to 18 kilometres over the equator, there is a transition zone with a width of two kilometres called the tropopause.
In this, the tropo character ceases and the new character starts.
Stratosphere:
It extends up to a height of 50 km from the surface above the troposphere.
It is stratified in nature.
The ozonosphere extends up to 15 kilometres over the poles and up to 22 kilometres over the equator.
The reaction between chlorine and ozone in the stratosphere is a catalytic cycle that leads to ozone depletion.
It begins when chlorofluorocarbons (CFCs) rise into the stratosphere and are broken down by ultraviolet radiation, releasing chlorine atoms (Cl).
The key reactions then occur in a cycle:
Cl + O₃ → ClO + O₂
ClO + O → Cl + O₂
In the first step, a chlorine atom reacts with ozone (O₃) to form chlorine monoxide (ClO) and molecular oxygen (O₂).
Then, the ClO reacts with a single oxygen atom (O) to regenerate the chlorine atom while producing another O₂ molecule.

TOPIC TO BE DISCUSSED IN THE NEXT CLASS: 'ATMOSPHERE' TO CONTINUE