Earth Data

Age: At least 4Y2 billion years.

Motion: Rotation (spinning motion around an imaginary
line connecting the North and South Poles) once every 23 hours, 56 minutes, 4.09 seconds. Revolution (motion around the sun)-once every 365 days, 6 hours, 9 minutes, 9.54 seconds.

Size: Polar diameter (distance through the earth from North Pole to South Pole)-12,713.54 kilometres. Equatorial diameter (distance through the earth at the equator)-12,756.32 kilometres. Polar circumference (distance around the earth through the poles)-40,008.00 kilometres. Equatorial circumfer­ence (distance around the earth along the equator)-40,075.16 kilometres. .

Area: Total surface area-509,700,OOO square kilometres. Land area-approximately 148,400,000 square kilometres, about 29 per cent of total surface area. Water area-approximately 361,300,000 square kilometres, about 71 per cent of the total
surface area.

Mass: 5.882 x 1021 tonnes.

Mean density: 5.517

Surface features: Highest land-Mount Everest, 8,848
metres above sea level. Lowest land-shore of Dead Sea, about 399 metres below sea level.

Ocean depths: Deepest part of ocean-area of the Mariana Trench in Pacific Ocean southwest of Guam, 11,033 metres below surface. Average ocean depth-3,730 metres.
Temperature: Highes'-58° C at AI Aziziyah, Libya. Lowest -89.6° C at Vostok Station in Antarctica. Average surface temperature-14° C.

Atmosphere: Heig!l'-more than 99 per cent of the atmosphere is less than 80 kilometres above the earth's surface, but particles of the atmosphere are 1,600 kilometres above the surface. Regions of atmosphere-troposphere (up to 10 or 16 kilometres above surface); stratosphere (from about 16 to 48 kilometres); mesosphere (from about 48 to about 80 kilometres); thermosphere (from 80 kilometres into outer space).
"Chemical make-up of atmosphere-about 78 per cent nitrogen, 21 per cent oxygen, 1 per cent argon, and small amounts of other gases.

Chemical make-up of the earth's crust (in per cent of the crust's weight): Oxygen 46.6; silicon 27.7; aluminium 8.1; iron 5.0; calcium 3.6; sodium 2.8; potassium 2.6; magne­sium 2.0; and other elements totalling 1.6.