What is Earth?

The earth is the 3rd planet from the sun between Venus and Mars. The earth is made up of several unique properties, characteristics, composition and they all affect the processes of the earth differently. Every of these properties and elements in Earth’s system are largely categorized into one of the four major subsystems including water, living things, land, and the air. These are regarded as the four interlocking “wonders” that create the earth’s diversity. Cumulatively, they are primarily grouped into biological (living things) and physical (non-living things).

These four “wonders” of the earth are dependent upon each other and have been used to make the study of biological and physical components of the earth easily comprehendible. They are scientifically called the biophysical elements namely the hydrosphere (‘hydro’ for water), biosphere (‘bio’ for living things), lithosphere (‘litho’ for land), and atmosphere (‘atmo’ for air). These spheres are further divided into various sub-spheres.

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According to Wikipedia,

Earth is the third planet from the Sun, the densest planet in the Solar System, the largest of the Solar System’s four terrestrial planets, and the only astronomical object known to harbor life. According to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago. Earth gravitationally interacts with other objects in space, especially the Sun and the Moon.

4 Different Spheres of the Earth

Lets take a look at these four spheres of the earth in bit more detail to understand how they help make up the earth.

  1. Hydrosphere (Water)

The hydrosphere includes all the gaseous, liquid, and solid water of the planet earth. The hydrosphere stretches all the way from the Earth’s surface downward numerous miles into the lithosphere and high above the crust into the atmosphere. Most of the water in the atmosphere is in gaseous form and as it rises higher into the atmosphere it condenses to form clouds which fall back on earth as precipitation.

All the water in the hydrosphere is always in motion just like the atmospheric gases. The natural earth features depicting the hydrosphere are the rivers, streams, lakes, seas, oceans and the water vapor. Glaciers, which are the slowly moving masses of ice, are also part of the hydrosphere. 97% of all earth’s water is salty. Oceans carry most of the salty water while the majority of lakes and rivers carry fresh water. The earth’s temperature is highly influenced by the hydrosphere.

Very low temperatures are associated with icebergs, glaciers or icecaps; low to moderate temperatures are associated with the common types of precipitation like snow, rain, drizzle, sleet or hails; and high temperatures are tied to dry and hot conditions and evaporation. The glaciers, icebergs, and icecaps are also categorically called the cryosphere.

  1. Biosphere (Living Things)

All the living things in the planet are categorized under the biosphere. In this view, the biosphere includes all of the animals, plants, and microorganisms of earth. Humans as well belong to this group. The entire ecological communities within the physical surrounding of the earth are within the umbrella of living things (biosphere). These ecological communities interact together with the physical aspects of the earth including the hydrosphere, lithosphere, and the atmosphere.

Collectively, these ecological communities are made reference to as biomes. Deserts, forests, grasslands, aquatic, tundra, and chaparral are the six main biomes that are present in the biosphere. The living things on earth interact with each other in various ways, which is well elaborated under the trophic levels of food chain – how energy is transferred in ecological systems.

  1. Lithosphere (Land)

The lithosphere is made up of all the hard and solid land mass on the earth’s surface, the semi-solid rocks (molten materials) underneath the earth crust, and the liquid rocks in the inner core of the earth. The surface of the lithosphere is uneven as it is characterized by various landform features. Some of the landforms include mountains like the Mount Fuji in Japan and Mount Vesuvius in Italy, deep valleys within the mountain ranges, huge plains like the ones in Texas and Brazil, extensive plateaus like Bolivian plateau in South America and the Colorado plateau of the United States, and hills like the black hills.

The liquid, semi-solid, and solid land components of the lithosphere form layers that are chemically and physically different. This is why the lithosphere is further divided into sub-spheres namely the crust, the mantle, the outer core, and the inner core. The crust is made of loose soil and rocks. The mantle is made of dense rock made up of nickel and iron in the form of silicate rocks and its lower part is semi-solid (partially molten) rocks.

The outer core is made up of liquid (purely molten) rock materials. The inner core is the centre of the earth which is purely made of very hot and liquid iron and nickel. The rock materials are divided into three primary categories based on how they are formed namely igneous rocks, sedimentary rocks, and metamorphic rocks.

  1. Atmosphere (Air)

All the air in the atmosphere makes up the atmosphere. The atmosphere is a mixture of nitrogen (about 78%), oxygen (about 21%), and other gasses (about 1%) such as carbon dioxide (0.039%), argon (0.93%) and the rest are trace gases (krypton, neon, helium , and xenon). The higher the atmosphere, the thinner it becomes and this trait gradually moves towards space. The atmosphere extends all the way from the earth’s crust to more than 6200 miles (10,000 kilometers) above the earth’s surface into space. The atmosphere is divided into several layers and amongst the layers is the stratosphere that contains the ozone layer which protects the organisms in the biosphere from the sun’s harmful radiation.

Other layers of the atmosphere include the troposphere, mesosphere, thermosphere, and the exosphere. These atmospheric layers exhibit different chemical compositions and temperatures, and the temperatures and chemical compositions widely vary within the different layers. The troposphere is where most of the weather happens and it becomes colder with altitude. The air is in constant motion around the planet and it is normally responsible for some natural events in the planet such as local breeze, winds, tornado, and tropical cyclones. The atmosphere is always in constant interaction with the hydrosphere, giving rise to the planets weather conditions.

Photo by: W-pix

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