Free
Antarctica is a frozen land. Ice covers almost all of the continent, which includes the South Pole.
The ice is several miles deep in places, covering all but the very tops of the highest mountains. Near the coast, glaciers crawl down the mountains and flow into the ocean. Glaciers are slow-moving rivers of ice and snow. Sometimes, chunks of the glaciers split off and crash into the ocean. They float away and become icebergs. Some of the chunks are as big as a city!
On the opposite side of Earth, an ice-covered ocean surrounds the Arctic, or North Pole. The ice cracks, crashes, and swirls on top of the currents. It shrinks in summer and expands in winter. But it never goes away. North and South, the polar regions of the Earth are strange and beautiful places.
Every kind of crystal has its own pattern. Snow crystals are hexagons, or six-sided figures. They join in different ways to form snow. The type of snow depends on many things. These include temperature, density (how packed the atoms are), and moisture. ▼
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A Glacier on the Move
The word glacier comes from the French word for “ice.” A glacier begins as a pile of snow in a mountain valley. As snow evaporates or melts, fresh snow replaces it. ▼
Snow weighs a lot. Layers of snow press down, forming a compact ice called firn.
Gravity goes to work on the firn. It makes the firn move down the mountain at a rate of several feet per day.
In places, deep cracks called crevasses form.
As the land becomes flatter, the glacier slows down. It begins to buckle, or collapse, in places. The buckling creates bumpy icefalls.
The tip of the glacier may move forward or backward. It depends on how much snow falls and how cold or warm it gets.
▲ The cracked ice pictured here looks like the ice sheets over the Arctic Ocean. But it’s not on planet Earth. This ice is covering Europa, a moon of Jupiter. Scientists believe Europa has a watery ocean under its icy shell. A place with liquid water might have life.
◀ Rime is frozen water vapor. Water vapor, or fog (a type of cloud), freezes on tree branches and other things. The wind blows the ice crystals sideways. The rime looks like a white, jagged flag on a branch.
Check It Out!
Why does lettuce get mushy when it’s frozen?
Lettuce is about 95 percent water. 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. They make a mushy mess!
Tropical Iceberg!
Most icebergs stay in polar or subpolar areas. They melt as they move into warmer winds and ocean temperatures. In 1894, an Antarctic iceberg set a latitude record. It broke off the continent and floated north. It was seen closer to the equator than any other known iceberg. It was spotted at a latitude of about 26° south. That’s about the same as Rio de Janeiro, Brazil. Rio is known for its beaches and year-round warm weather!
▲ Each winter in St. Paul, Minnesota, artists make giant castles. They use ice blocks from frozen lakes and rivers. Since 1886, the ice castles have been world-famous.
