The Arctic is the area around the North Pole, at the top of the Earth. But where does it start? Most scientists define the Arctic as the area inside the Arctic Circle, a line of latitude at about 66.5 degrees north. It holds the Arctic Ocean basin and the northern parts of Scandinavia, Russia, Canada, Greenland, Iceland and Alaska. Some scientists use another line. They define the Arctic as the area north of the tree line, where the landscape is frozen and dotted with shrubs and lichens. The tree line broadly matches where the average July temperature stays at or below 10 degrees Celsius (50 degrees Fahrenheit).

Most of the Arctic is ocean. As of November 2026, the Arctic Ocean is the smallest of the world's five ocean basins, at about 14 million square kilometers (5.4 million square miles). It is also the shallowest of the five and the least salty, because of low evaporation and large amounts of fresh water from rivers and glaciers. Its deepest part, the Canada Basin, reaches 5,441 meters (17,850 feet). Year-round ice cover has made it isolated and little explored.

Many Arctic animals have ways to hide or stay warm. Arctic foxes have white winter coats that help them blend into snow and ice. In summer the coat turns brown or gray, which helps them hide among the rocks and plants. A snowy owl may eat more than 1,600 lemmings a year, which is three to five every day. How many lemmings there are may decide how far south the owls travel. Musk oxen have long guard hairs over a shorter undercoat that adds warmth in winter. When threatened by wolves, a herd forms a ring with the young in the middle and the horns facing outward.

Polar bears live in the Arctic and eat seals. The polar bear is the largest of the bear species alive today. A polar bear's fur looks white, and it has black skin underneath. Its hair is made of clear, hollow tubes filled with air, so the bears only look white. Oils from food, sunlight and other residue can make the fur look cream or yellow.

Walruses use their long tusks to haul their bodies out of the water and to break breathing holes in the ice from below. Both males and females have tusks, which are large canine teeth that keep growing all their lives. Belugas live in small groups called pods and talk to each other with clicks, whistles and clangs. They can also mimic other sounds. Caribou and reindeer are the same species, Rangifer tarandus. Caribou are native to North America, and reindeer are native to northern Europe and Asia.

Antarctica works differently. There are no countries in Antarctica. Seven countries made claims to Antarctic territory before the Antarctic Treaty of 1959, and the treaty does not legally recognize any claims. The Southern Ocean is the water around Antarctica. The United States recognizes it as reaching from the Antarctic coast to 60 degrees South, but not all countries agree on its edge. Six kinds of seal live in the waters around Antarctica. Mount Erebus, on Antarctica's Ross Island, is the southernmost active volcano on Earth.

Both ends of the Earth have lights in the sky. Above the Arctic Circle the Sun does not rise on about December 21, and in winter the Arctic is dark and cold. The northern lights are called aurora borealis, and the southern lights are called aurora australis. One bird sees both poles. Arctic terns hold the record for the longest migration of any animal, flying each year from the Arctic to the Antarctic. That is the record as of November 2026.

Words to know

• latitude: distance from equator
• lichens: tiny living things
• migration: long seasonal trip