amazing facts about the earth

PLANET
EARTH

Earth formed about 4.5 billion years ago, but it was a 
very different place then. Its surface was a hot inferno
of mostly molten rock, with little or no liquid water
and no oxygen in atmosphere. Since then Earth has
developed oceans, continents, an oxygen-rich
atmosphere - and life.

THE CHANGING EARTH

Look at map and it will show you the position of the continents, but
in fact our world is always changing. Earth's surface is split up into
large slabs called tectonic plates. The plates steadily shift around,
carrying continents and oceans with them. When they collide, new
mountain rages are pushed up. Afterwards, over millions of years,
wind, water, and ice gradually wear the mountains down.

                 250 MILLION  YEAR AGO,

         EARTH'S CONTINENTS ALL            JOINED TOGETHER, FORMING           AN ENORMOUS SUPERCONTINENT          KNOW  AS PANGAEA

UNIQUE PLANET 

Earth is the only place in the Universe known to support life.
It is thought that life developed after water began to collect on
Earth's surface. Eventually, tiny life forms evolved that could
survive on water, sunlight, and a few chemicals in water.
These microbes added oxygen to the atmosphere - an essential
step for development of planets and animals.

Earth's atmosphere

The atmosphere of Earth is made up several
different gases.

Photo by The New York Public Library on Unsplash

• NITROGEN - 78%

A gas that can be "fixed" in the soil, as well as
loose in the atmosphere. Plants need nitrogen
from the soil to survive.

• OXYGEN - 21%

Essential for animals to breath. Oxygen was absent
until microbes evolved that could use sunlight to
turn carbon dioxide and water into carbohydrates,
releasing oxygen.

• ARGON - 0.9%

An inert gas (one that doesn't
react with other substance).

• Carbon dioxide - 0.1%

These include carbon dioxide (CO2), which was once abundant,
but is now mostly incorporated into materials such as limestone rock.

Inside our planet

Earth's interior has layers. Scientists discovered this by studying paths

by which earthquake waves pass through the planet.

Thickness (km)

• Crust - 6 - 90 km (3.7 - 56 miles)

• Mantle - 2,880 km (1,790 miles)

• Outer core - 2,225 km (1,400 miles)

• Inner core - 1,215 km (755 miles)

 CRUST

Different types of  crust make up Earth's land and its ocean  floor.

The crust under the land is thicker and contains more rock types.

MANTLE

This rocky layer is denser than the crust. It is mostly solid,

although it can very slowly deform and flow.

OUTER CORE

The only liquid layer the outer core is mainly iron but also

contains some nickel and small amounts of  other substances.

INNER CORE

This is solid , and is mostly iron with nickel. Its temperature

is very hot - about 5,400°C (9,900°F).

What's in a layer?

Earth's crust and mantle are mostly made of  minerals called

silicates, which are a combination silicon dioxide and metal-

oxides. The mantle is rich magnesium-containing silicates,

whereas the two different types of crust have less magnesium

and more aluminium and calcium. The core is dominated by

metallic iron. No part of it has ever been brought to the 

surface, but its composition has been worked out by 

scientific methods such as studying earthquake waves.

The oceans

Earth's surface and atmosphere contain the equivalent 

1.39 km³ (333 million miles³) of water. There are regions

of deep ocean as well as shallow seas that over areas around

the edges of the continents - these are called continental shelves.

Earth's surface has not always been as dominated by liquid water.

In the past, during ice ages when the polar ice caps were much

thicker and more extensive, so much water became locked up

in them that sea level was at least 120 m (400 ft) lower than

it is today, exposing the continental shelves as dry land.

Water world

Almost three - quarters

of  Earth's surface is

water. Over 97 per cent

of  Earth's water is found

in the oceans.

Continental drift

Over millions of  years, tectonic plates have moved, shifting

around the continents on Earth's surface. Chucks of continents

split away and push into each other, creating new land masses

and moving the oceans in a process called "continental drift"

200 MILLION YEARS AGO 

( North America, Europe, and parts of Asia are one landmass)

The supercontinent Pangaea has just began to break into two

main landmasses.

130 MILLION YEARS AGO

(India moves north , Australia is joined to Antarctica)

India has escaped from the southern landmass, and is 

slowing moving north, towards Asia.

70 MILLION YEARS AGO

(South America separates from Africa)

South America has split from Africa , while in the north,

North America is splitting from Europe.

TODAY 

(Australia moves into the pacific Ocean)

Australia has separated from Antarctica, and India has

collided with Asia, forming the Himalayas.

Plate movement

The continents get rearranged because they are carried along

as part of moving plates. This process has been going on for billions

of years, and is thought to be caused by slow, heat - driven movements

in the Earth's mantle.

Yearly shift

Plates typically move at a rate of about 2.5 (1 in) in a year. That's about

as fast as your fingernails grow. Some move faster - up to 10 cm (4 in) a year

A spinning planet

Earth's gravity would pull it into the shape of  a sphere, but its rotation

makes it bulge slightly. This means its diameter at the equator 

is 41 km (25 miles) more than the distance between its poles.

 Not quite round 

At the moment, scientists think that Earth's equatorial bulge is growing

at rate of  7 mm (0.3 in) every 10 years.

Magnetic Earth

Because Earth's outer core is liquid, the planet's rotation stirs it into motion.

This causes electric current to develop in the liquid iron itself. Any pattern of

electric currents creates a magnetic field, and in Earth's case, the field is 

similar to what would be produced by a large bar magnet inside the planet.

The field protects Earth from damage by harmful, energetic particles that come from the Sun.

The magnetic field

The magnetic poles do not coincide exactly with the geographic (rotational)

poles, and they gradually change position over time.