Physical Geography (UPSC) (Part-II)

The forces which influence the ocean currents are as follows:–

Planetary Winds
• The movement of water on the surface of the ocean is influenced by the wind blowing over it. The friction between the wind and the water’s surface impacts the direction and speed of the water’s movement.
• It is important to understand that the wind affects the momentum of the water, but it does not initiate the movement.
• A notable example of the impact of prevailing winds on ocean currents can be observed in the North Indian Ocean.
• In this region, the direction of the current completely changes when the monsoon winds reverse.

Temperature
• The movement of ocean water, both on the surface and below it, is initiated by temperature differences. The temperature of the ocean water at the equator differs significantly from that at the poles.
• The solar energy heats the water, causing it to expand. As a result, there is an 8 cm gradient between the elevated equatorial water and the middle latitude. This gradient causes the water to flow downhill.
• Due to its lower density, the warm water moves from areas of lower density to areas of higher density. On the other hand, the denser cold water sinks.
• The warm equatorial water slowly moves towards the poles along the surface, while the colder polar water slowly creeps along the bottom towards the equator.

Salinity
Water with high salinity is denser than water with low salinity. Thus, denser saline water sinks below, while the relatively lighter water tends to rise.

Coriolis Force
• The Coriolis Effect influences the movement of oceanic currents by providing them with direction.
• This effect occurs due to the Earth’s surface rotating faster at the equator compared to the poles. It affects the paths of various moving objects, such as currents, winds, and airplanes, that are only loosely connected to the ground.
• Specifically, in the northern hemisphere, the Coriolis force causes the water to move to the right, while in the southern hemisphere, it causes the water to move to the left.

Coastal Configuration
The coastal alignment and presence of underwater ridges play a role in determining the direction of ocean currents. The shape of the land also influences the flow of these currents. For example, the equatorial current is divided into two branches after encountering the Brazilian coast.

About The Atmosphere

• The atmosphere, ever-changing, consists of layers of gases that surround the Earth, sustain life, and provide an environment in which the planet exists.
• Consisting predominantly of nitrogen (78%) and oxygen (21%), and trace amounts of argon, carbon dioxide, water vapor, and many other gases, it plays the role of balancing the energy budget of the Earth.
• Split into layers such as the troposphere, stratosphere, mesosphere, thermosphere, and exosphere, the atmosphere regulates temperature, induces weather phenomena, and blocks dangerous solar radiation through the ozone layer from reaching life.
• The troposphere, being nearest to the Earth, supports weather and climate, while the ozone in the stratosphere blocks ultraviolet rays of the sun.
• Besides, the atmosphere allows water to cycle through precipitation, somehow ensuring that ecosystems remain viable.
• A favorable atmospheric composition and equilibrium mean life, but mankind jeopardizes this equilibrium through pollution and greenhouse gas emissions. If we want to retain life on Earth for a while longer, we must save this thin layer.

• The savanna is a unique tropical biome characterized by vast open grasslands interspersed with scattered trees and shrubs. Found in regions like Africa, South America, Australia, and parts of Asia, it is defined by its warm climate and distinct wet and dry seasons.
• During the wet season, the savanna bursts into life with lush greenery, supporting diverse species of plants and animals. In the dry season, water sources shrink, and the landscape becomes arid, challenging its inhabitants to adapt for survival.
• The savanna is home to iconic wildlife such as elephants, lions, giraffes, and zebras, along with a variety of birds and insects. Its plant life, including drought-resistant grasses and acacia trees, has adapted to withstand periodic fires and low rainfall.
• This ecosystem plays a vital role in global ecology, serving as a carbon sink, a habitat for biodiversity, and a resource for local human communities.

Geographical Features and Locations

The revolution of Earth has the following impact:

Seasons: Due to the 23.5° tilt of Earth’s axis, different hemispheres receive varying sunlight during revolution, leading to spring, summer, autumn, and winter.
Length of the Year: Revolution defines the calendar year and seasonal cycles.
Solar Energy Distribution: The angle at which sunlight strikes the Earth varies with revolution, affecting ecosystems, agriculture, and climatic zones.
Eclipses: Revolution, combined with the Earth-Moon system, results in solar and lunar eclipses depending on relative alignments.
Tides: While primarily influenced by the Moon, the Sun’s position relative to the Earth (during revolution) intensifies tides, creating spring and neap tides.

The decreasing order of proportion of freshwater in different forms is as follows: snow caps, icebergs, and glaciers > groundwater > freshwater lakes atmosphere > rivers.

Geothermal energy is the heat received from the earth's core. This heat continuously flows outward. It transfers to the surrounding layers of rock, the mantle. When temperature and pressure becomes very high some mantle rocks melt becoming magma. It then either comes out as lava or heat up the nearby rocks and water which comes out as hot springs or geysers.

Gravitational force is constantly working on all physical bodies. It is giving weights to objects with mass and causes them to fall to the ground when dropped. Plate movement is a dynamic change on the surface of the earth.

It explains many aspects of the interrelationship of volcanoes, earthquakes, climate change, and the evolution of life itself. Everything about our planet is related either directly or indirectly to plate tectonic. Rotation causes day and night. Revolution causes seasons, change in the length of day and night.

The revolution of Earth has the following impact:

Seasons: Due to the 23.5° tilt of Earth’s axis, different hemispheres receive varying sunlight during revolution, leading to spring, summer, autumn, and winter.
Length of the Year: Revolution defines the calendar year and seasonal cycles.
Solar Energy Distribution: The angle at which sunlight strikes the Earth varies with revolution, affecting ecosystems, agriculture, and climatic zones.
Eclipses: Revolution, combined with the Earth-Moon system, results in solar and lunar eclipses depending on relative alignments.
Tides: While primarily influenced by the Moon, the Sun’s position relative to the Earth (during revolution) intensifies tides, creating spring and neap tides.

About the Equatorial Climate

• Equatorial climate, also known as tropical climate, is found near the equator, between the Tropic of Cancer and Tropic of Capricorn.
• This climate is characterized by high temperatures and significant rainfall throughout the year.
• Due to its consistent warmth, equatorial regions experience little seasonal variation, maintaining a nearly constant climate with temperatures typically ranging from 25–30°C (77–86°F).
• The heavy rainfall, often exceeding 2000 mm annually, supports lush vegetation, making it ideal for dense rainforests.
• These regions are home to extraordinary biodiversity, including unique plant and animal species.
• The consistent climate fosters the growth of various tropical crops like bananas, cacao, and palm trees.
• However, equatorial regions are also prone to extreme weather events such as thunderstorms and hurricanes.
• Deforestation and human activities, like agriculture and urbanization, pose significant threats to the ecosystems in these areas.
• Despite these challenges, equatorial climates play a crucial role in regulating the Earth’s climate and maintaining global biodiversity.

This is the reason that the temperatures of the Oceans are moderate while that of continents is extreme. The moderating effect on temperature of the land due to proximity of the seas is called Maritime influence. The increasing effect on temperature of the land at interior of the continents is called Continental Influence.