EARTH

History of Earth

• Earth and the other planets in the Solar System formed 4.54 billion years ago.

• About 535 million years ago there have been five mass extinctions. • The last extinction event occurred 65 million years ago, when a

meteorite collision probably triggered the extinction of the (non-avian) dinosaurs and other large reptiles years ago.

• The development of photosynthesis allowed the Sun's energy to be harvested directly by life forms; the resultant oxygen accumulated in the atmosphere and resulted in a layer of ozone (a form of molecular oxygen [O3]) in the upper atmosphere

Graphics in Solar SystemEarth: • the third planet.• the fifth largest planet. • the densest planet.• has only one satellite, the Moon. • has distance – 149600000 km from the

Sun.

Atmosphere of Earth

• The atmospheric pressure on the surface of the Earth averages 101.325 kPa, with a scale height of about 8.5 km.

• The Earth's atmosphere is composed mainly of nitrogen (77%), oxygen (21%), argon (.93%), and carbon dioxide (0.03%).

• Layers:troposphere

stratosphere mesosphere ionosphere lithosphere biosphere hydrosphere

Composition

• Chemical: 34.6% Iron 29.5% Oxygen 15.2% Silicon 12.7% Magnesium 2.4% Nickel 1.9% Sulphur 0.05% Titanium

• Mass atmosphere = 0.0000051

oceans = 0.0014

crust = 0.026

mantle = 4.043

outer core = 1.835

inner core = 0.09675

FACTS ABOUT EARTH

• Earth is the only planet whose English name does not derive from Greek/Roman mythology.

• The Earth is 4.5 to 4.6 billion years old, but the oldest known rocks are about 4 billion years old.

• There is no record of the critical period when life was first getting started.

• The oxygen in Earth's atmosphere is produced and maintained by biological processes.

• Earth has a modest magnetic field produced by electric currents in the outer core

Moon

• It is called Luna by the Romans, Selene and Artemis by the Greeks, and many other names in other mythologies.

• It is the second brightest object in the sky after the Sun• As the Moon orbits around the Earth once per month, the angle

between the Earth, the Moon and the Sun changes• Moon was first visited by the Soviet spacecraft Luna 2 in 1959• The first landing was on July 20, 1969 and the last was in

December 1972 • The gravitational forces between the Earth and the Moon cause

tides.• The Moon's gravitational attraction is stronger on the side of

the Earth nearest to the Moon and weaker on the opposite side • The Moon has no atmosphere • The Moon's crust averages 68 km thick • Most rocks on the surface of the Moon seem to be between 4.6

and 3 billion years old.

Earth Day is celebrated on 22nd April to inspire the peoples to make the Earth

green and free from pollution and save from extinction.

• To conserve wild life, trees and environment the International Environment Day is celebrated on 5th June.

Satellites• First artificial satellite launched by Soviet Union is Sputnik-1 in 1957.• TypesCommunicational ObservationalNavigationalWeatherResearch• Satellites orbits vary depending on purpose of satellite and

classified as:-Low earth orbitPolar orbitGeostationary orbit

Mountains

• highest mountain in world is Mount Everest(8848m) in Asia.• Tallest mountain in world is Mouna Kea in Hawaii.• Types Volcanic Domed Folded Plateau Fault-block

Minerals

• Minerals can be classified acc. to chemical composition.

• Types of minerals 1. Silicates 2. Carbonate 3. Sulphate 4. Halide 5. Oxide 6. Sulphide 7. Phosphate 8. Element 9. Organic

Rocks• The Earth's lithosphere is made of rock.• Types Igneous Metamorphic Sedimentary• Rocks are classified by mineral and chemical composition• Rocks are used to construct buildings and infrastructure.

Volcanoes• Volcano is an opening of a planets surface which allows hot, molten

rock, ash, and gases to escape from below the surface.

• Volcanoes are generally found where tectonic plates are pulled

apart or come together. .• Mid-Atlantic Ridge- example of volcanoes caused by "divergent

tectonic plates“. • the Pacific Ring of Fire- example of volcanoes caused by

"convergent tectonic plates”. • Volcanoes also formed by- Stretching and thinning of the Earth's crust called "non-hotspot

intraplate volcanism“.

Mantle plums called “Hotspot volcanoes” found elsewhere in the

solar system, especially on rocky planets and moons.

Meteoroids

• If you have a dark clear sky you will probably see a few meteroids per hour on an average night.

• During one of the annual meteor showers you may see as many as 100/hour.

• Very bright meteors are known as fireballs.• One of the Martian meteorites, known as ALH84001 (left), is

believed to show evidence of early life on Mars• The largest found meteorite Hoba, in Namibia weighs 60 tons.• A very large number of meteoroids enter the Earth's

atmosphere each day amounting to more than a hundred tons of material

• The sound of the explosion of meteroid fall in Tunguska was heard half-way around the world in London..

• One of these hits the Earth about once in a million years or so on the average

•

Global warming

Pollution • long-term rising levels of

atmospheric gases cause slight but critical increases in the acidity of ocean waters, and the possible effects of this on marine ecosystems.

• raised levels of toxic gases in the atmosphere affect the Earth's climate.

Green house effect• it is increase in

temperature of Earth. When incoming solar radiation is passed but outgoing thermal radiation is blocked by the atm. then environmental temp. increases which cause global warming. Carbon dioxide and water vapor

are its major factors.

Ozone layer

• The ozone layer" refers to the ozone within stratosphere, where over 90% of the earth's ozone resides. Ozone is an irritating, corrosive, colorless gas with a smell something like burning electrical wiring. In fact, ozone is easily produced by any high-voltage electrical arc (spark plugs, Van de Graff generators, Tesla coils, arc welders). Each molecule of ozone has three oxygen atoms and is produced when oxygen molecules (O2) are broken up by energetic electrons or high energy radiation.

Depletion of ozone layer• a slow, steady decline of about

4% per decade in the total volume of ozone in Earth's stratosphere (ozone layer) since the late 1970s,

• Tropospheric ozone depleting events which occur near the surface in polar regions during spring.

• Ozone depleting substances

CFCs

Freon

Halones

Hole in ozone layer• The ozone hole is

not technically a “hole”

where no ozone is present,

but is actually a region of exceptionally depleted ozone in the stratosphere over the Antarctic

• Blue and purple colored area centered over Antarctica is seen on October 4, 2004.

Indication towards end of Earth

• Global warming.• Ozone hole.• Unbalanced rain.• Very high temp. during summer.

Preventions

• Education programme.• Stop illegal dumping.• Awareness.• Green movement.