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The continent of Antarctica is a land of ice. Almost the entire continent, which includes the South Pole, is covered with ice.
The ice blanket is several miles deep in parts, covering all but the very tops of the highest mountain peaks. Near the coast, glaciers (slow-moving rivers of ice and snow) crawl down the mountains and flow into the ocean. Sometimes, chunks of the glaciers, some as large as a city, split off, crash into the ocean, and float away to become icebergs.
At the opposite end of the Earth, an ice-covered ocean surrounds the Arctic, or North Pole. The ice cracks, crashes, and swirls on top of ocean currents. The ice cover shrinks in summer and expands in winter, but it never disappears. North and South, the polar regions of the Earth are unusually beautiful places, frozen with ice.
Every kind of crystal has its own regular structure of atoms. Snow crystals are hexagons (six-sided figures). These crystals combine in various ways to form snow. The type of snow formed depends on temperature, density (how packed the atoms are), moisture, and other factors. ▼
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A Glacier on the Move
Glaciers (from the French word for “ice”) begin as piles of snow in mountain valleys. As some snow evaporates or melts, freshly fallen snow replaces it. ▼
Snow is heavy, and layers of it press down to form a compact ice called firn.
Gravity causes the firn to travel down the mountain at a rate of several feet per day.
Deep cracks in the ice, called crevasses, form in some places on the glacier.
As the land becomes flatter, the glacier slows down. It begins to buckle, or collapse, in places, and this process creates bumpy icefalls.
The tip of the glacier advances and retreats, depending on the snowfall and the temperature.
▲ The cracked ice pictured here looks eerily like the ice sheets that cover the Arctic Ocean. Yet it’s not on planet Earth. It’s on Europa, a moon of Jupiter. Scientists believe Europa has a liquid, watery ocean under its icy shell. Where there is liquid water, there might be life.
◀ Rime is frozen water vapor. This frozen water vapor, or fog (a type of cloud), freezes on tree branches and other solid objects. The wind blows the ice crystals horizontally (parallel to the horizon). The rime looks like a white, jagged flag on a tree branch.
Check It Out!
Why can’t you freeze lettuce without turning it into a mushy mess?
Lettuce is about 95 percent water, and pure water freezes into ice at 32°F. Ice takes up more room than water and is harder and sharper. The ice crystals break through the cells of the lettuce, creating a mushy mess.
Tropical Iceberg!
Most icebergs melt while still in polar or subpolar regions as they encounter warmer and warmer winds and ocean temperatures. In 1894, an Antarctic iceberg set a latitude record. It broke off the continent of Antarctica and floated north. It was spotted closer to the equator than any other known iceberg. Its record-breaking latitude, about 26° south, is parallel to that of Rio de Janeiro, Brazil. Rio is known for its beaches and year-round warm weather!
▲ Each winter in St. Paul, Minnesota, artists create giant castles. They use a building material that is common in winter—blocks of ice from Minnesota’s frozen lakes and rivers. Since 1886, the ice castles of St. Paul have been world-famous.
