The Earth – Facts About Home Planet

The Earth 

 Key Concepts

• Crust
• Mantle
• Core
• Hydrosphere
• Atmosphere
• Biosphere
• Lithosphere

Introduction

To understand the motions of other bodies in the solar system and the universe, scientists need to understand the basic motions of the Earth. The change in seasons and  the weather of a place depends on the movements of Earth. The Earth is a unique planet because it is the only planet in the solar system with water on its surface; it supports life, and its atmosphere contains 21% of the oxygen needed for the survival of life. 

Earth Basics 

The third planet from the Sun in the solar system is the Earth. It is mostly made of rocks and  was formed about 4.6 billion years ago. Around 71% of the Earth’s surface is covered with a thin layer of salt water known as the global ocean. When the Earth is seen from space, it looks blue sphere covered with white clouds, but it has the shape of an oblate spheroid or flattened sphere. 

  Sphere Oblate Spheroid 

Due to the spinning of the Earth on its axis, the polar regions flatten and the equatorial zones bulge. The circumference of the Earth from pole to pole is 40,007 km and its equatorial circumference is 40,074 km. 

Earth’s interior: 

The Earth’s layer is defined as the thickness of a material put on it. These layers mainly consist of rock and iron. There are 4 layers, namely – Crust, Mantle, Outer Core, and Inner Core 

Crust:  

It is the thinnest outermost layer of the Earth. The crust under the oceans is called the oceanic crust. It is 5 to 10 km thick and consists of silica and alumina. 

The continental crust is the crust that makes up the continents. It’s thickness is between 15-80 km thick. Its thickness is very high below the mountain ranges. Continental crust is the land where we live. 

Mantle: 

Mantle lies below the crust and is denser than the crust. It is almost 2900 km thick and makes up almost 2/3rd of the Earth’s mass. The mantle is divided into the upper and lower mantle. It mainly comprises of silicate rocks that are rich in iron and magnesium. There is continuous up and down movement of rocks in this layer  due to the internal heat from the core area. This heat form the convective currents which cause rock plates to move and collide with each other that results in earthquakes. 

Outer core: 

This layer is next to the mantle. T is present in the liquid state at the 5000 degree centigrade temperature. The outer core comprises nickel and iron. These two metals are in liquid state due to tremendous heat in the outer core. The outer core creates a magnetic field around the Earth due to constant circulatory motion of it. The benefit of this magnetic field is that it protects the Earth from the Sun’s damaging solar wind. This layer is very important because without this layer the Earth will not have a magnetic field and without a magnetic field, there will not be any life, ocean, and atmosphere. 

Inner core:

This layer is the hottest layer on the Earth with a temperature of 7000 degrees centigrade. It is hotter than the Sun’s surface. It is present below the outer core and comprises iron and nickel. Though it is the innermost layer, it is present in the solid state because it is under high pressure from the weight of layers present above it. 

Structural zones of Earth’s interior 

The three compositional zones of Earth’s interior are – lithosphere, asthenosphere and mesosphere. The uppermost portion of the Earth’s mantle is cool and brittle. This uppermost part and the crust above it form the lithosphere. It is a rigid layer with 15 to 300 km thickness. The area below the lithosphere is less rigid known as asthenosphere. It is about 200 – 250km thick. Due to tremendous heat and pressure, the rock of asthenosphere has the capacity to flow. This ability of flow is known as plasticity. Below asthenosphere, there is a layer of solid mantle rock called mesosphere. 

Features of Earth 

Earth’s magnetic field extends beyond the atmosphere and affects the area of space known as magnetosphere. Earth is affected by gravity. Gravity is the force of attraction exists between all matter present in the universe. Earth uses a gravitational force that pulls the things towards its center. 

Energy in the Earth System 

Scientist study the way matter and energy interact with each other to create and help Earth’s living things and living conditions. The Earth system consists of four spheres that are storehouse and powerhouse of all the matter of planet. The four spheres of Earth are – geosphere (land), hydrosphere (water), atmosphere (air) and biosphere (living things). 

Geosphere: 

It is the solid part of the Earth that includes rocks, mountains, hills, sand dunes and soils on the surface of the ocean floor and on the continents. 

Hydrosphere: 

All the water present on the Earth is collectively called as the hydrosphere. Hydro means ‘water.’ Earth’s all water bodies such as rivers, pond, lakes, oceans, glaciers, and groundwater are parts of hydrosphere. Majority of the Earth’s surface is covered with water and 97% of  this water is present in oceans that is salty water. The remaining 3% is fresh water present in underground, lakes, river, streams, glaciers, and in the polar regions. 

Atmosphere: 

The layer of gases that surrounds the Earth’s surface is know as atmosphere. ‘Atmos’ means air. Atmosphere consists of all gases essential for the survival of living things. Air consists of 78% of nitrogen, 21% oxygen and 1% other gases. Atmosphere also contains dust particles, pollutants, water vapor and pollens. 

Biosphere: 

Biosphere involves all life on the Earth, i.e., plants, animals, and human beings. It includes all kinds of life such as microorganisms in the soil, water, air, life under water. The habitat of all living things makes up part of biosphere. Following images show the habitat of living things in the biosphere. Biosphere contains any organic matter that is not decomposed. Once the organic matter is decomposed it becomes the part of other spheres such as lithosphere, hydrosphere, and atmosphere. The biosphere can extend from ocean to few kilometers above atmosphere. 

Summary

• Earth is the place where we live. It is the third planet from the Sun.
• Earth is made up of various layers – crust, mantle, outer core, and inner core.
• Earth is also called water planet or blue planet due to the presence of water on it.
  Crust is the thinnest outermost layer of the Earth.
• Mantle is mainly made up of silicate rocks that are rich in iron and magnesium.
• Outer core is present in liquid state at the 5000 degree centigrade temperature.
• Inner core is the hottest layer of the Earth with the temperature of 7000 degree
  centigrade. Earth is affected by gravity.
• The four spheres of the Earth are – geosphere (land), hydrosphere (water), atmosphere (air) and biosphere (living things).