Know The Planet Where We Live.

 Earth is one of the planets in the solar system and one of the four made of rocks. Earth is unique because it is the only planet that supports life. The distance from the sun makes it neither hot nor too icy cold. It helps the existence of water here in liquid form. Earth has an oxygen-rich atmosphere. Oxygen and water are two key factors that allow life to flourish on Earth. 

From the analysis of meteorites, Geologists believe that the earth may be from the solid piece of an exploded planet. Meteorites are natural objects that fall to the earth from space. They are composed of iron or stone or a mixture of both. The two main types are chondrites and achondrites.

Achondrites Meteorites.

More than 70% of the earth's surface is water. Above sea level, the earth's land surface has seven land masses called continents. Earth is in a constant state of change above and below sea level. Most volcanoes and earthquakes are due to the movements of rocky plates in the earth's crust.

The ten highest mountains in the world are all in the Himalayas, which lie between Tibet, China, and the Indian subcontinent.

Earth facts:

Diameter: 12,756 km at the equator and 12,713 km at the poles.
Age: 4.6 billion years
Distance from the sun: 150 million kilometers
Mass:5854 billion billion tonnes
Area: 29.2% land and 70.8% water
Orbiting time: 365.26 days
Orbiting speed 28.9 km/sec.
The highest point above sea level: Mt. Everest (Asia), 8848 m
Highest point below mean sea level: Bentley sub-glacial trench (Antarctica), -2538 m
Largest lakes and inland sea: Lake Superior (Canada),82098 sq. km and Caspian Sea (Asia), 370980 sq. km
The largest river: the Nile (Africa) 6695 km
Desert: Sahara (Africa), 9065000 sq. km
Ocean: Pecefic ocean, 165,241,000 sq. km
Waterfall: Angel waterfalls in Venezuela 979 m (discovered by James Angel, a US pilot in 1935).

Deserts:

Few places on earth are as stark and hostile as a desert. Deserts are areas where very little rain falls (under 100 mm a year). Any rain that does fall quickly evaporates. Soil can not develop in such a dry environment, and the survival of plants is impossible. The landscape is bare sand, gravel, or rocks. Clear skies and sparse vegetation leave the ground exposed to extremes of temperature. In the tropics, cloudless skies can create temperatures up to 50 degrees Celsius. Desserts at high altitudes are cold all day.

The world's great deserts lie within the continents, far from the ocean. They are also along the tropic of Cancer and Capricorn on either side of the equator. The sinking air in that region creates stable dry weather.

Desertification is the effect of drought and heavy grazing by cattle, sheep, etc. Heavy grazing destroys vegetation cover and turns the area permanently into the desert.

The climatic condition creates a different type of deserts. Sometimes, it causes the shrinking and expansion of the desert. History revealed that the Sahel, the southern margin of the Sahara, was watered by summer rains. In recent years, the lack of rain in the Sahel has caused drought and farming problems.

Desert features:

Strong wind piles the sand upwards in dunes

Flash floods curve canyon-like valleys

Extreme heat creates corrosive chemicals that sculpt rocks into bizarre shapes.

Oasis:

An oasis is a fertile area within a desert near an underground stream or spring. Crops such as date palms can grow there. Through irrigation, we can create an artificial oasis.

Mirage:

Mirages happen when light passes through two layers of air with different temperatures. The sun heats the sand, resulting in the heat of the air above it. The hot air bends light rays and reflects the sky. When we see it from a distance, the air masses with different temperatures collide and appear as a mirror. An optical illusion that the desert ahead seems like a lake. It is a reflection of the sky above. On a sunny day, we can observe the mirage on hot tar roads.

Richter Scale:

Charles F. Richter discovered the Richter scale in 1935. It measures the magnitude (the size of the shock wave and the energy it produces). The worst volcanic eruption ever recorded was in 1815 in Tambora, Indonesia, with a fatalities rate of 92,000.

The intensity and probable effects of earthquakes on Earth are:

Intensity	Probable effects
1	Not felt by people but recorded by the instrument.
2	Felt by people resting
3	Detected indoors, hanging objects swing
4	Doors rattle, trees shake
5	Felt outdoors by most people, objects move
6	Felt by everyone, windows break
7	Difficult for people to stand. Bricks and tiles fall
8	Major damage to buildings, tree branches break
9	Damage to foundations, some buildings collapse
10	Large landslides, destruction of buildings
11	Major ground destruction, railway lines buckle
12	Destruction in full swings, river courses alter

 

The Earth's Structure:

Scientists discovered that the earth has an egg-like structure. The Center is a yolk of metals surrounded by a rock called the mantle. The outer shell of the hard rock is called the crust.

More than 80 elements occur naturally on earth. The bulk of earth is made of iron(35%), oxygen (28%), magnesium (17%), silicon (13%), a small amount of nickel (2.7%), sulfur (2.7%), calcium (0.6%) aluminum (0.6%), and a tiny proportion of other elements (0.6%). 

Elements occur naturally on earth Iron (top one) and aluminum (bottom)

​​The Earth is made up of three different layers: the crust, the mantle, and the core. 

Earth has different layers in its structure, and they are different physically and chemically. The outer solid layer is called the crust. Other layers are the mantle, outer core, and inner core. The mantle is a highly viscous layer. The outer core is a liquid layer, and the solid center is called the inner core. We can discover the boundaries between these layers using a seismograph, which shows vibrations bounce off the layers during earthquakes. Between the Earth's crust and the mantle is a boundary called the moho. The oblate spheroid shape is because of slightly flattened poles and bulging at the equator.

 Let us discuss one by one.

Crusts:

Crusts are of two types: oceanic and continental. The solid rocks make the crust, made of elements like Silicon, oxygen, and Aluminium. Because of this, it is called sial (silicon = Si; aluminum = Al) or felsic.

Significant features:

The crust is the outermost part of the earth.

• · The thickness of the crust varies under the oceanic and continental areas.
• · The oceanic crust is thinner as compared to the continental crust.
• · The continental crust is thicker in the areas of mountain systems.
• · The crust is made up of heavier rocks having a density of 3 g/cm³.
• · The kind of rock seen in the oceanic crust is basalt.
• · The mean density of material in the oceanic crust is 2.7 g/cm³.
• · Silica (Si) and Aluminium (Al) are major constituent minerals. 

Mantle:

The mantle is the layer of the Earth right below the crust, made of oxygen, silicon, and the heavier element magnesium. It is known as sima (Si for silicon + ma for magnesium) or mafic. It is up to 2900 km.

The uppermost part of the mantle is solid and forms the base of the crust, made of the heavy rock peridotite. The crust and the upper part of the mantle make up the lithosphere It is in a solid state.

• · It has a density higher than the crust portion.
• · The thickness ranges from 10-200 km.
• · The mantle is from Moho’s discontinuity to a depth of 2,900 km.
• · The asthenosphere is the upper portion of the mantle.
• · It is the chief source of magma that finds its way to the surface during volcanic eruptions.
• · The crust and the uppermost part of the mantle are called the lithosphere.
• · The major constituent elements of the mantle are Silicon and Magnesium, and hence, it is also termed sima

Core:

The core is made of solid iron and nickel and is at about 5000 to 6000 °C, which is about the temperature of the photosphere of the Sun.

• The outer core is a liquid layer below the mantle.
• The inner core is the very center of the earth.[1]
• The core-mantle boundary is positioned at a depth of 2,900 km.
• · The inner core is in the solid state, whereas the outer core is in the liquid state.
• · The core is made up of heavy material composed of nickel and iron. Hence, it is also called the nife layer

Moho

The moho is the boundary between the Earth's crust and the mantle, discovered by Andrija Mohorovičić in 1909. He found that seismograms showed two kinds of seismic waves. There is a shallow, slow wave that arrives first, then followed by a deep, fast wave. He observed that the speed of the deep wave changed as it got just below the mantle. The reason for the increase in speed was that the material of the mantle was different from that of the crust.

The discontinuity lies 30–40 km below the continental surface and less deep below the ocean floors. [1]

Drilling hole: 

Geologists have been trying to get at the moho for decades. During the late 1950s and early 1960s, Project Mohole did not get enough support. The Soviet Union reached a depth of 12,260 meters (40,220 ft) over 15 years before abandoning the attempt in 1989. [2]

Reaching the discontinuity is still a significant scientific target. One proposal considers a self-descending tungsten capsule. The idea was to fill the capsule with radioactive material. It would give off enough heat to melt the surrounding rock, and the capsule would go down due to gravity. [3]

The Japanese project Chikyū Hakken ("Earth discovery") plans to use a drilling shop to drill down through the thinner ocean crust. In 2012, the Scientific deep-sea drilling vessel Chikyu set a new world record by drilling down and obtaining rock samples from deeper than 2,111 meters below the seafloor off the Shimokita Peninsula of Japan in the northwest Pacific Ocean. [4,5]

Macquarie Island:

Macquarie Island, off Tasmania, is at the meeting point of two oceanic plates: the Pacific Plate and the Indo-Australian Plate. The composition of the island from the material pushed up from deep in the Earth's mantle. Now, ophiolite is on the surface because the two plates are scrunching together. It is the only place on Earth where this happens now. [6] There are other places where ophiolite is present but brought up many millions of years ago. Ophiolites are present in all the major mountain belts of the world. [6,7]

References:

1 Levin H. 2006. The Earth through time. 8th ed, New York: Wiley. Chapter 7, p184. ISBN 0-471-69743-5.

2 Ozhovan M. et al 2005. Probing of the interior layers of the Earth with self-sinking capsules. Atomic Energy. 99, 556–562 (2005). Probing of the Interior Layers of the Earth with Self-Sinking Capsules,  Atomic Energy. 99 (2): 556–562. doi:10.1007/s10512-005-0246-y. S2CID 918850.

3  A report on the findings does not appear to be published yet. The following link is to the planning proposal, April 30, 2012. [1]

4  That is the junction between the bottom of the Earth's crust and the top of the Earth's mantle.

5  Macquarie Island - UNESCO World Heritage Centre. Whc.unesco.org. Retrieved on 2013-07-16.

6  Ben-Avraham Z. et al 1982. The emplacement of ophiolites by collision. Journal of Geophysical Research: Solid Earth (1978-2012) 87 (B5) 3861-3867

7 Wikipedia.

8 Encyclopedia.