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 System
• the third planet.
• the fifth largest planet.
• the densest planet.
• has only one satellite, the Moon.
• has distance – 149600000 km from the
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%).
FACTS ABOUT EARTH
• Earth is the only planet whose English name does not derive from
• 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
• The oxygen in Earth's atmosphere is produced and maintained by
• Earth has a modest magnetic field produced by electric currents in
the outer core
• 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
• The gravitational forces between the Earth and the Moon cause
• 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
• To conserve wild life, trees and
environment the International
Environment Day is celebrated on 5th
• First artificial satellite launched by Soviet Union is Sputnik-1 in 1957.
• Satellites orbits vary depending on purpose of satellite and
Low earth orbit
• highest mountain in world is Mount Everest(8848m) in Asia.
• Tallest mountain in world is Mouna Kea in Hawaii.
• Minerals can be classified acc. to chemical
• Types of minerals
• The Earth's lithosphere is made of rock.
• Rocks are classified by mineral and chemical composition
• Rocks are used to construct buildings and infrastructure.
• 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
• 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
Mantle plums called Hotspot volcanoes” found elsewhere in the
solar system, especially on rocky planets and moons .
• 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
• 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
Green house effect
• long-term rising levels of • it is increase in
atmospheric gases cause temperature of Earth.
slight but critical When incoming solar
increases in the acidity of radiation is passed but
ocean waters, and the outgoing thermal
possible effects of this on radiation is blocked by
marine ecosystems. the atm. then
• raised levels of toxic increases which cause
gases in the atmosphere global warming. Carbon
affect the Earth's climate. dioxide and water vapor
are its major factors.
• 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 Hole in ozone layer
• a slow, steady decline of about • The ozone hole is
4% per decade in the total not technically a “hole”
volume of ozone in Earth's
stratosphere (ozone layer) where no ozone is present,
since the late 1970s, but is actually a region of
• Tropospheric ozone depleting exceptionally depleted ozone
events which occur near the in the stratosphere over the
surface in polar regions during Antarctic
spring. • Blue and purple colored area
• Ozone depleting substances centered over Antarctica is
CFCs seen on October 4, 2004.
Indication towards end of Earth
• Global warming.
• Ozone hole.
• Unbalanced rain.
• Very high temp. during summer.