The continents look fixed, but the positions of the continents are always changing. Earth's outer layer is broken into about a dozen large plates, and the plates rest on the hot, molten rock of Earth's mantle. North America and Europe are moving away from each other at about 2.5 centimeters, or 1 inch, per year.

The idea began with a map. According to the Library of Congress, the first suggestion that the continents appeared to fit together was made by the cartographer Abraham Ortelius. Alfred Wegener proposed continental drift in the early 1900s, with three articles published in 1912 suggesting the continents are slowly moving. Wegener argued that more than the shape of the landmasses proved his theory. Evidence for one single continent grew over the next decades, but it took several more decades for most scientists to accept continental drift.

The picture that emerged was of one great landmass breaking up. By 240 million years ago almost all of the world's land was joined in a single huge continent. By about 200 million years ago it began to break apart. The big supercontinent was called Pangaea. Its pieces became today's continents. The breakup is not finished. The Great Rift Valley is a site of major tectonic activity, where the continent of Africa is splitting into two.

Counting continents is partly a question of what the rock is like beneath the water. Geographers classify Australia as a continent because it sits on its own continental crust, and it is surrounded by the Indian and Pacific Oceans. In February 2017 a research team led by New Zealand's geoscience agency GNS Science proposed that Zealandia, a 4.9 million square kilometer region of the southwest Pacific Ocean, is a continent. Roughly 94 percent of it is underwater.

Antarctica shows how much ice a continent can hold. Together the Antarctic and Greenland ice sheets contain more than 99 percent of the land ice and over 68 percent of the fresh water on Earth. Scientists often discuss the Antarctic Ice Sheet as three regions: the large East Antarctic Ice Sheet, the smaller West Antarctic Ice Sheet and the Antarctic Peninsula. The Antarctic Ice Sheet contains about 30 million cubic kilometers of ice. If all of it melted, sea level would rise about 58 meters.

The coldest place on Earth is on the East Antarctic Plateau, but not at the highest peak. The coldest spots sit in hollows just downhill from a ridge. As of November 2026, the lowest air temperature ever measured on Earth is -89.2 degrees Celsius, at Vostok Station on 21 July 1983. Temperatures in Antarctica, much lower than Arctic temperatures, plunge lower than -73 degrees Celsius. Penguins and seals make their homes there even though it is covered in ice.

Bellingshausen reported seeing an ice shore of extreme height in the last week of January 1820. In January 1773 Captain Cook became the first recorded European navigator to cross the Antarctic Circle. Borchgrevink's 1899 expedition was the first to spend a winter on the Antarctic mainland. Roald Amundsen was the first person to reach the South Pole, in December 1911. The Antarctic Treaty was signed in Washington on 1 December 1959 by twelve countries, and it guarantees freedom of scientific investigation.

Some land is young and some is old. The Cascade Range is young: some of its peaks began to form only about one million years ago. The ice age that covered much of North America reached its peak about 18,000 years ago. Some trees in North America's coastal rainforest grow to more than 90 meters tall and three meters across. The Mississippi River is 3,730 kilometers long, one of the longest river systems in the world.

Here are more places measured in numbers. The Volga River drains Europe's largest watershed, about 1.38 million square kilometers. The Bay of Bengal, covering almost 2.2 million square kilometers, is the largest bay in the world. The Orinoco River flows in a giant arc for more than 2,736 kilometers. The altiplano of Peru and Bolivia has an elevation of about 3,700 meters. The Amazon rainforest can hold as many as 100 tree species on a single acre, and more than 2 million insect species are native to the region.

The count of continents differs between groups. The Olympic five-continent model leaves out Antarctica because it is uninhabited. The United Nations and the International Olympic Committee often leave it out because it has no permanent population and no sovereign nations. The United Nations groups the world into five regions rather than seven continents.

Words to know

• Pangaea: old supercontinent
• plates: moving pieces
• cartographer: map maker
• watershed: drained land
• altiplano: high plain