The Earth and the Universe
Concept: The Earth and the Life on it
The Earth is the third planet from the Sun in the solar system. It is a huge planet whose surface is mostly covered with water. It belongs to the category of terrestrial planets.
Measurement of the Earth:
- Scientists believe that the Earth is not a perfect sphere; rather it resembles an oblate sphere.
- The Earth's total surface area is 509,7000,000 sq. km, out of which 361,300,000 sq. km is covered with water. The surface covered with water makes up 71% of the total surface area of this planet.
- The diameter of the Earth is 12,742 km. If compared to the size of the Sun, then the diameter of the Earth is 109 times smaller than that of the Sun.
Distance of the Earth from the Sun:
- The Earth is 93 million miles away from the Sun.
- The distance between the Earth and the Sun is measured in Astronomical Unit (AU).
- Light from the Sun takes eight minutes to reach the surface of the Earth.
- The Earth comes closest to the Sun in early January. This distance is called perihelion.
- It is, however at the farthest distance from the Sun in early July. This distance is called aphelion.
Motions of the Earth:
The Earth shows two types of motions—Rotation and Revolution.
- It denotes the circular movement of the Earth on its axis.
- The Earth takes 24 hours to complete one rotation on its axis. It leads to the occurrence of day and night.
- It signifies the circular movement of the Earth around the Sun in a fixed elliptical path called the orbit.
- The Earth takes 365 days, 6 hours and 9 minutes to complete one revolution around the Sun. This duration is considered a year.
- These extra 6 hours yearly combine to add one extra day every fourth year, which is called a leap year and has 366 days.
Atmosphere on the Earth:
- The Earth is surrounded by an envelope of a mixture of gases.
- The gases in the air, along with their percentage, are as follows—
- Nitrogen: 71%
- Oxygen: 21%
- Carbon dioxide: 0.03%
Landforms on the Earth:
- The Earth has a variety of landforms due to the significant variation in temperature and climatic conditions across the globe.
- The landmass is divided into different continents, as shown in the image below—
- India is a part of Asia, the largest continent on Earth.
- Australia is the smallest continent in the world.
- The continent of Africa is occupied by 54 countries, the highest among all other continents.
- South America is known for its natural wonders. The longest mountain range—the Andes, the highest waterfall—Angel Falls and the driest place— Atacama Desert are located on this continent.
The different landforms found on the Earth are discussed below—
- Mountains and Hills:
- Mountains and hills are found on all seven continents.
- These are considered the tallest geographical structures on Earth.
- The mountains are usually found in long ranges and form 20% of the landmass of the Earth.
- The highest mountain peak in the world is Mount Everest, located in the Himalayas.
- Hills are also elevated landmasses but smaller than mountains.
- Examples: Mountains—Himalayas, Andes, Rockies; Hills: Aravalli Hills,Malabar Hills.
- It is an elevated area that sharply rises above its adjoining area. Plateaus, unlike mountains, have flat tops, due to which they are also called tableland.
- Example: Deccan Plateau, Ethiopian Plateau.
- These are depressed areas usually found between mountains or hills.
- Valleys are generally drained by rivers and lakes.
- The different types of valleys are river valleys, glacial valleys and rift valleys.
- Example: Yosemite Valley and Kangra Valley.
- Vast stretches of flat land are called plains.
- They can extend from 10 acres to 1000 acres.
- Plains are usually fertile tracts of land and are suitable for agriculture.
- Plains can be flat or gently undulating.
- Example: Indo-Gangetic Plains, West Siberian Plains
- The driest areas on Earth which receive very little rainfall are called deserts.
- Less precipitation leads to a scorching climate in which some specific species of flora and fauna are found.
- They approximately cover 1/3rd of the landmass on the Earth.
- There are both hot and cold deserts with extreme climatic conditions.
- Example: Sahara desert in Africa is the largest desert in the world, and the Thar desert is the largest in India.
- They resemble bowls. These are depressions with sides higher than the bottom.
- Basins are drained by rivers and their tributaries.
- Example: The largest river basin in the world is the Amazon river basin.
- Oceans and Seas:
- A large area covered with saltwater is called an ocean. A sea is a part of an ocean which remains fully or partially enclosed by land.
- 71 % of the Earth is covered with oceans and seas.
- 70% of the biotic components found on the Earth are aquatic. It means that aquatic plants release 70% of the oxygen found in the atmosphere.
- Oceans have an average depth of 12,100 feet.
- Example: The Pacific Ocean is the world’s largest ocean, whereas the Arctic Ocean is the smallest.
- These are large bodies of water surrounded by land.
- Lakes can be both freshwater and saltwater lake in nature.
- Water in the lake can be either stagnant or slow-moving.
- Example: Lake Baikal and Lake Superior. Arctic Ocean is the smallest.
- These are naturally flowing bodies of water and usually move downhill.
- Rivers have freshwater.
- Rivers get their water from the melting of glaciers or are rain-fed.
- Rivers usually drain into seas, oceans or lakes.
- Example: River Nile, River Ganga, River Thames
Life on the Earth:
- Due to the availability of life-supporting factors, our planet is home to many animal and plant species, including humans.
- The present species found on the Earth have evolved gradually over a long period in which the environmental factors have played a vital role.
- The easiest evolution one would be able to relate is that of humans from the early men to the present Homo sapiens.
Homo sapiens: : The scientific term for human beings.
Glacier: A gradual moving mass of ice or snow.
Depression: A region which is at a lower level compared to the surrounding area.
Oblate sphere: A shape which is flat at the poles and bulging at the Equator.
Did You Know?
- The Earth rotates around an imaginary line that runs through the north and south poles.
- Imaginary horizontal and vertical lines are running through the surface of the Earth, which are called latitudes and longitudes.
- The Equator is a latitude that divides the Earth into two hemispheres—Northern and Southern Hemispheres.
- The heat of the Sun is maximum at the places falling on the Equator.
- The longitude named Prime Meridian divides the Earth vertically into Eastern and Western Hemispheres.