Who first explored the South Seas?

Although other explorers had briefly passed through the region, Captain James Cook, a British explorer, was the first person to explore thoroughly the South Pacific region, including...

Who were the earliest explorers?

About 50,000 years ago, the first explorers sailed from Southeast Asia to colonize Australia and New Guinea, which were joined together at that time. Later, people crossed from Siberia...

How is the strength of an earthquake measured?

The strength and location of earthquakes are measured by an instrument called a seismograph, which can detect ground movements. Sometimes the movements from an earthquake can be detected...

What happened in the great San Francisco earthquake?

The last time the San Andreas Fault slipped, it caused the worst disaster in San Francisco's history. The earthquake happened in April 1906. It devastated the city by damaging buildings...

What is the San Andreas Fault?

The San Andreas Fault is a long crack in the Earth's crust that extends 970 km through California, in the USA. It runs along the edges of the tectonic plates carrying the Pacific Ocean...

What causes earthquakes?

Earthquakes are evidence of movement of the tectonic plates that carry the continents. Most of the areas where earthquakes take place are along the edges of plates. Friction holds the...

How do we know that the climate has changed?

In more recent times, geologists and palaeontologists have been able to make more accurate measurements of the age of ancient rocks. Trees produce a new 'ring' every year, and these...

What is an Ice Age?

Ice Ages were periods when large parts of the Earth's surface were covered by sheets of ice. Each Ice Age has lasted about 100,000 years, with gaps between of up to 20,000 years when...

When did life first appear?

The first signs of life are thought to have appeared about 3,000 million years ago. Some rocks from this time contain substances that are characteristic of life, although fossils appear...

How do dams affect the environment?

Most dams are built to meet people's growing demand for water, but sometime dams cause unforeseen environmental damage. Dams are usually built across valley entrances, creating enormous...

What are the effects of deforestation?

Many areas of tropical rainforest are burned to provide farmland, but the effects of this deforestation can be disastrous. After the forest is burned, new fertile ground is exposed....

Hole in one

In the 1970s, scientists discovered a gap in the protective ozone layer around the Earth. Ozone, a form of oxygen, filters out more than 90 percent of the Sun's damaging ultraviolet...

What was the Chernobyl disaster?

In 1986 an explosion in a nuclear power station in the Ukraine was the worst ever nuclear accident. Large amounts of radioactive material were released into the atmosphere, and many...

What is acid rain?

Rain containing dissolved acids falls to the ground, damaging trees, crops and other wildlife as well as harming water supplies. Acid rain is caused by air pollutants such as nitric...

Why did prehistoric animals become extinct?

There are many opinions about why extinctions occurred. Many people believe that it was the result of asteroids or meteorites striking the Earth. There is evidence of ancient impacts...

How are fossils formed?

Fossils result from the death of an animal millions of years ago. The soft parts rot quickly, and the bones or shell are scattered by scavenging animals. Some of these remains are buried...

How old are fossils?

Ancient history has been divided up into eras, which are periods of time identified by the fossilized forms of life from that period. The oldest era, called the Paleozoic, contains...

What are fossils?

Fossils are the traces of ancient animals and plants found buried in rock. Sometimes a fossil retains the shape and structure of the hard parts of an animal, such as fossilized dinosaur...

How thick is the ice at the South Pole?

The thickest ice at the South Pole is 4,800 m deep - that's ten times the height of a tall skyscraper. The ice covers a huge area of 14 million sq km, which is bigger than the whole...

How big are icebergs?

Some icebergs are bigger than an entire country. The biggest iceberg ever recorded was larger than Belgium, with an area of 31,000 sq km. These giant icebergs break away from the polar...

What are glaciers?

Glaciers are large masses of ice that form on land and move slowly under their own weight. They are found in cold mountainous places or polar regions. Some glaciers are huge continuous...

Why does snow fall?

Snow forms when water vapor inside a cloud freezes into tiny crystals. The water vapor usually crystallizes around a tiny dust particle called a nucleus, and the snow crystal continues...

What is a tsunami?

Tsunamis are waves that are often caused by an undersea earthquake. The tsunami rushes along at up to 970 km/h, building into a wall of water 30m high as it approaches land. Tsunamis...

How big are hurricanes?

Hurricanes can measure between 320 and 480 km across. They travel at speeds of 16 to 24 km/h, growing larger and stronger as they move. Usually they travel vest, then swing east as...