The Cullinan, once the largest uncut diamond, was discovered in South Africa in 1905. It was the size of a man's fist and weighed over half a kg (1 lb). The largest gem cut from it, named the 'Star of Africa', is in the British Royal Sceptre in the Tower of London.
The huge flightless emus of Australia's scrubland may roam hundreds of kilometres in a year in search of food and water. In 1932, both farmers and the Royal Australian Artillery had to battle about 20,000 emus which were attacking crops. Eventually, a barrier fence 1,000km (620 miles) long was put up to protect the farms.
The ozone layer is a layer of concentrated ozone gas about 24 km (15 miles) up in the atmosphere. It protects us from the Sun's harmful ultra-violet rays. However, this vitally important layer is being destroyed through the use of aerosol cans containing chloro-fluoro-carbons or CFC's.
The earth has more than 600 active volcanoes. Many of them are to be found on what is called the 'Ring of Fire' around the Pacific Ocean. The largest active volcano on the Earth today is the Mauna Lau, which is about 4168 metres (13,677 feet) high. It is situated in the Hawaiian islands. One volcanic explosion in Mauna...
About 6 million tonnes of salt is made from the sea every year. This is enough to build a salt version of the Great Pyramid in Egypt. In hot countries, people use a very simple method to collect salt from the sea. Huge, shallow pans are arranged along the coast. These fill up with sea water as the tide...
Sea cucumbers look harmless but they have a dramatic way of fending off enemies. If a hungry fish comes too close, the sea cucumber shoots out streams of sticky threads which look like spaghetti. These entangle the attacker, giving the sea cucumber time to make a getaway.
Grey whales spend the summer feeding in the Arctic. Then they swim south along the Pacific coast to breed near Mexico, returning north in the spring. This is a round trip of 20,000 km (12,500 miles), about the same distance as a trip from London in England to Auckland in New Zealand.