63 The Cryosphere-Mid

The Cryosphere FOCUS Question What is the cryosphere, and why is it important to Earth?

Welcome to the Iceworld The blue planet. The watery planet. The blue marble. Earth has earned these nicknames because it's covered by so much water, but most of it is salty ocean water. Only about 3 percent is fresh water. Surprisingly, most of that fresh water is locked up as solid ice. Welcome to the icy cryosphere (KRY-oh-sfeer)— all the different types of frozen water on Earth. Its main components are glaciers, snow cover, floating ice, and permafrost. Bundle up and let's explore this iceworld. Word Wise The word cryosphere comes from the Greek language. Kryos- means "cold" and -sphere relates to Earth's round shape.

Glaciers What rules the cryosphere? Glaciers! These icy giants are by far the main component of the cryosphere. Glaciers are slow-moving masses of ice and snow that occur in some of the coldest places on Earth. They are found in the Arctic region near the North Pole, in the Antarctic region near the South Pole, and high up in some mountains around the globe. Ice sheets are a type of glacier that cover large areas of land near the poles. Another type of glacier is the alpine glacier. These glaciers form in low spots in and around mountains worldwide. Wowser! Ice can be ancient. Some glacial ice covering Antarctica has been there for almost a million years.

Snow Cover Have you ever built a snowman or gone sledding? If so you know snow—the softer side of the cryosphere. Snow is a form of frozen precipitation that covers the ground in polar and other cold regions during winter. When the air cools to below freezing—0°C (32°F)— water droplets in clouds form ice crystals called snowflakes. If the ground is also below freezing, falling snow can build up and cover the surface. Unlike glaciers, snow cover is temporary, forming when it's cold and melting when it's warm. Snowmelt contributes to the flowing water in streams and rivers.

Floating Ice You can't ice-skate or play ice hockey without large areas of flat ice. In bodies of water, ice floats and stays at the surface because it is less dense than liquid water. Most of Earth's floating ice. is frozen ocean water called sea ice Sea ice forms near the poles when salty ocean water freezes. Sea ice covers a vast area of Earth's surface—more than twice the size of Canada. Icebergs are chunks of floating ice that form when pieces of glaciers near a coast break off and fall into the ocean. Unlike sea ice, icebergs are made of fresh water. Floating ice also forms in lakes and rivers when the top layers of fresh water freeze in winter.

Permafrost Did you ever notice that the ground gets firmer when the temperature drops? When the weather is warm, liquid water fills up tiny spaces in the soil. When the temperature drops, the water freezes and so does the ground. The ground usually thaws in summer. But in places that don't have warm weather, the ground stays frozen all year long. Ground that is permanently frozen— or frozen for at least two years—is called permafrost. Permafrost is only a small part of the cryosphere. Yet almost one-quarter of Earth's exposed ground contains permafrost. You can find it on high mountains, like the Rockies, and in the Arctic and Antarctic.