In 1783 an Icelandic eruption threw up enough dust to temporarily block out the sun over Europe.
A huge underground river runs underneath the Nile, with six times more water than the river above.
Lake Bosumtwi in Ghana formed in a hollow made by a meteorite.
Beaver Lake, in Yellowstone Park, USA, was artificially created by beaver damming.
Off the coast of Florida there is an underwater hotel. Guests have to dive to the entrance.
Venice in Italy is built on 118 sea islets joined by 400 bridges. It is gradually sinking into the water.
The Ancient Egyptians worshipped a sky goddess called Nut.The world's windiest place is Commonwealth Bay, Antartica.
In 1934, a gust of wind reached 371 km/h on Mount Washington in New Hampshire, USA. American Roy Sullivan has been struck by lighting a record seven times.
The desert baobab tree can store up to 1000 litres of water in its trunk. The oldest living tree is a California bristlecone pine name 'Methuselah'.
It is about 4600 years old. The largest tree in the world is a giant sequoia growing in California. It is 84 meters tall and measures 29 meters round the trunk.
The fastest growing tree is the eucalyptus. It can grow 10 meters a year.
The Antartic notothenia fish has a protein in its blood that acts like antifreeze and stops the fish freezing in icy sea.
The USA uses 29% of the world's petrol and 33% of the world's electricity.
The industrial complex of Cubatao in Brazil is known as the Valley of Death because its pollution has destroyed the trees and rivers nearby.
Tibet is the highest country in the world. Its average height above sea level is 4500 meters. Some of the oldest mountains in the world are the Highlands in Scotland. They are estimated to be about 400 million years old.
Fresh water from the River Amazon can be found up to 180 km out to sea.
The White Sea, in Russia, has the lowest temperature, only -2 degrees centigrade.
The Persian Gulf is the warmest sea. In the summer its temperature reaches 35.6 degrees centigrade.
There is no land at all at the North Pole, only ice on top of sea.
The Arctic Ocean has about 12 million sq km of floating ice and has the coldest winter temperature of -34 degrees centigrade.
The Antarctic ice sheet is 3-4 km thick, covers 13 million sq km and has temperatures as low as -70 degrees centigrade.