Earth

Radius: 6,371 Km
Age:4.543 billion years
Distance From Sun:149.6 million Km
Galaxy: Milky Way
Permanent Gases: Nitrogen, Oxygen, Argon

When we look at the landscape, it all seems quite still and and unaltered. But, very slowly , Earth is continually changing. The surface of the Earth changes position following the movements of tectonuc plates. It would take many millions of years, for example: North and South America to seperate at Panama, or Africa to break from Asia at Suez.

Volacanic eruptions, Earthquakes and Flood change the appearance of the earth and the Oceanic Crust. The rain, the rivers, the seas and ice all erode or wear away the rocks, taking away debris and putting this in different places, thus changing the appearance of the landscape.

An earthquake can split the ground in a few seconds. Lava from a volcanic eruption can spread over the land destroying everything near by in minutes. A heavy rainstorm can flood a n entire city in a day.

AVALANCHES

Sometimes, because of sudden changes of temperature, great blocks of snow or ice break away from mountains and descend to the bottom at speed. This is known as avalanche.It is one of the cause of landscape change in cold regions.

They are a part of nature and have been happening for thousands of years.

Earthquakes

An earthquake also known as a quake, tremor or temblor is the perceptible shaking of the surface of the Earth, resulting from the sudden release of energy in the Earth's crust that creates seismic waves. Earthquakes can be violent enough to toss people around and destroy whole cities.

Shaking and ground rupture are the main effects created by earthquakes, principally resulting in more or less severe damage to buildings and other rigid structures. The severity of the local effects depends on the complex combination of the earthquake magnitude, the distance from the epicenter, and the local geological and geomorphological conditions.

The ten largest recorded earthquakes have all been megathrust earthquakes. However, of these ten, only the 2004 Indian Ocean earthquake is one of the deadliest earthquakes in history.

Floods

A flood is an overflow of water that submerges land which is usually dry. Flooding may occur as an overflow of water from water bodies, such as a river, lake, or ocean, or it may occur due to heavy rainfall.

The primary effects of flooding include loss of life, damage to buildings and other structures, including bridges, sewerage systems, roadways, and canals.

Tsunami

A tsunami also known as a seismic sea wave, is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explosions, landslides, glacier calvings, meteorite impacts and other disturbances above or below water all have the potential to generate a tsunami.

Tectonic Plates

Tectonic plates are pieces of Earth's crust and uppermost mantle, together referred to as the lithosphere. The plates are around 100 km thick and consist of two principal types of material: oceanic crust and continental crust. The composition of the two types of crust differs markedly, with basaltic rocks dominating oceanic crust, while continental crust consists principally of lower density granitic rocks.

In the history of Earth many tectonic plates have come into existence and have over the intervening years either accreted onto other plates to form larger plates, rifted into smaller plates, or have been crushed by or subducted under other plates.

Plate tectonics has been responsible for many of the features that we find on the surface of the Earth today.

  • The Appalachian Mountains were formed from wrinkling of the Earth's surface produced by the collision of the North American and African plates.
  • The seismic and volcanic activity of the West Coast of the United States, the San Andreas Fault is produced by the grinding of the Pacific and North American Plates against each other.
  • The Dead Sea in Israel is part of a rift system produced by plates that are pulling apart in that region.
  • The Himalayan Mountains were formed (indeed are still growing) as a result of the Indian subplate burrowing under the Eurasian plate and raising its edge.

Plate tectonics is still an active process, and will drastically reshape the face of the Earth over the next 50 million years or so. Some of the Future assumptions are :-

  • Portions of California will separate from the rest of North America.
  • The Italian "boot" will disappear.
  • Australia will become linked to Asia.
  • Africa will separate from the Near East.

What How Why

What is a Light Year?

The unit of measurement used to calculate distances in space is called Light Year. It is the distance which light travels in one year. 1 Light-Year = 9460 billion km. (approx)