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The ice man: an intrepid photographer shoots glacier caves around the world.

When he finished his work on a cruise ship in the summer of 2005, photographer Eric Guth stayed behind in Alaska to hike the Mendenhall Glacier. While hiking, he squeezed through a crack in the huge ice mass and into a mesmerizing cavern. Sweeping walls of ice glowed shades of blue. Streams flowed over the rocky floor, and water dripped from the ceiling.

Guth had stumbled upon a glacier cave, carved into the ice by water and wind. Since then, he has explored glacier caves around the world--no easy task, since the caves are hard to reach and risky to enter. His spectacular photographs, which have earned him the nickname "the Ice Man," reveal scenes that no one will ever be able to capture again, as the caves are constantly changing.

ON THE MOVE

In his search for elusive glacier caves, Guth hikes mountains in far-off places like Alaska, Switzerland, and Argentina, where the conditions are ideal for glaciers to form.

"The key thing you must have to form a glacier is that some winter snow has to survive through the summer," says Ed Waddington, a glaciologist at the University of Washington. New snow adds its weight to the pile each winter, usually for centuries. Eventually the heavy snow compacts the lower layers into dense, glacial ice. Blue Glacier--a relatively small glacier in Olympic National Park in Washington State--contains enough ice to make 20 trillion ice cubes!

The thick ice is the secret to the blue hues in Guth's photos. Light is composed of all colors of the rainbow. Ice absorbs the red wavelengths of sunlight more than it does the blues. That means that the blues move through the ice and reach our eyes.

Because of their immense weight, glaciers slowly slide downhill. As snow falls in the accumulation zone at the top of a glacier, snow melts in the warmer ablation zone at the bottom (see Anatomy of a Glacier, p. 9). "The upper part is growing, and the bottom part is shrinking," says Waddington. A glacier is always moving, but when accumulation keeps up with melting, it doesn't appear to change position.

Guth camps out for days, trekking around the ablation zone in search of openings. The sound of rushing water tips him off that a cave may be nearby. Water from melting snow flows along the glacier's surface and down into a crack, where it bores out a vertical shaft called a moulin. Water flowing down moulins and through other cracks combines to create streams inside the glacier.

"It's just like a river in 3-D," says Waddington. The rushing water carves out a glacier cave--and provides stunning scenes.

SHIFTING ICE

Although the sound of water helps Guth locate caves, there are other sounds he doesn't want to hear when he's inside one---the cracks and groans of shifting ice. Since water and wind are constantly changing the caves, it's hard to predict when one might collapse.

Once, when Guth was inside a cave entrance in Patagonia, he fell through thin ice. His entire body plunged into freezing water--but he managed to hold his camera just above the surface! To prevent hypothermia, a condition in which your body temperature drops dangerously, Guth's friends wrapped him in all the dry clothes they could gather before hiking back to camp.

Ice caves' shape-shifting nature adds danger to Guth's work, but it also adds motivation. He wants to photograph their beauty before the caves change--or vanish altogether. "Over the winter, many parts of these tunnel systems will actually squeeze shut," explains Waddington. "What keeps them open in the summer is that water is continually flowing through them and melting off the edges of the tunnel." When Guth returns to a glacier, he often finds that caves he photographed the year before have disappeared.

ON THE RETREAT

Guth isn't the only one paying attention to changing glaciers. Scientists warn that many of the world's glaciers are shrinking because of rising temperatures (see Disappearing Glaciers, left). This is a major concern, since the huge ice masses hold 75 percent of the world's freshwater supply. "[Glaciers are] indicators of climate change because they're sensitive to temperatures and precipitation," says Howard Conway, a glaciologist at the University of Washington. As temperatures rise, an increasing amount of precipitation falls as rain rather than snow. "So you're getting a lot less accumulation at the top of the glacier," he says. Meanwhile, melting increases in ablation zones. Glaciers continue to slide downhill, but they appear to recede upward as ablation outpaces accumulation.

To study some glaciers, scientists go on backpacking treks like Guth's. Antarctic glacier studies often involve monthlong expeditions with airplanes and snowmobiles, and maneuvers around dangerous crevasses--deep cracks in the ice. Scientists not only measure how glaciers are changing, but also try to figure out how thick they were in the past. "If we can understand why things have changed in the past, it can give us some hope to understand how they'll change in the future as well," says Conway.

Guth hopes his photos will help document how glaciers change from the inside. He snaps the shots no one will ever be able to see again, capturing glimpses of fleeting glacier caves before they vanish into the ever-changing ice.

ANATOMY OF A GLACIER

A glacier forms when snowfall exceeds snowmelt. As snow accumulates, it compresses into glacial ice and begins to move.

ACCUMULATION ZONE: Where snow builds up. When a glacier's mass grows great enough, it becomes too heavy to maintain its rigid shape and begins to move downhill.

TERMINUS:

The end point of a glacier.

ABLATION ZONE: The lower part of a glacier, where warmer temperatures cause the ice to break apart and melt.

EQUILIBRIUM LINE: Where the accumulation of snow is equal to the amount that is melting or breaking apart.

DISAPPEARING GLACIERS

Glaciers around the world are melting. As they disappear, critical freshwater supplies, hydroelectric power, and tourism are all at risk.

MONTANA: Glacier National Park's namesake glaciers are expected to vanish by 2020.

ALASKA: About 98 percent of glaciers are thinning and/or retreating.

EUROPE:

Mountain glaciers are shrinking in size and number.

ASIA: About 90 percent of Himalayan glaciers are melting.

NEW ZEALAND:

Retreating glaciers have lost about half of their volume since the 1850s.

SOUTH AMERICA: Glaciers in the Andes Mountains in Peru and Bolivia have lost a third of their area in the past 40 years.

AFRICA: Most mountain glaciers in Africa could be gone by 2030.

ANTARCTICA: Ice shelves are collapsing, freeing coastal glaciers.

SOURCE: EARTH POLICY INSTITUTE

WHAT DO YOU THINK?

Eric Guth often puts himself in danger to get good photos of an ice cavel. Is the benefit to science worth the risk?

STANDARDS

NATIONAL SCIENCE EDUCATION STANDARDS:

Grades 5-8: Structure of the Earth system

Grades 9-12: Origin and evolution of the Earth system

COMMON CORE STATE STANDARD:

LITERACY IN SCIENCE: 3. Follow precisely a multistep procedure when carrying out experiments.

OBJECTIVE

Understand the characteristics of glaciers and the caves that form inside them.

BEFORE READING

* Where do glaciers usually form? (in cold regions like mountaintops and near polar regions)

* What is a glacier cave? (a cave that forms inside a glacier instead of in rock)

* What kinds of dangers might scientists and explorers face inside ice caves? (falling into deep cracks in the ice, hypothermia, collapsing caves, etc.)

* Many glaciers around the world are melting. What is causing that melting? (rising temperatures on Earth)

LESSON

1. Go to www.scholastic.com/scienceworld. Open up the digital edition to page 8. Use the mask tool to hide everything but the title and the image of the man in the cave. Ask students what they observe about the picture. What is it? In which part of the world do they think it might be? (The man is standing inside a glacier cave in Switzerland.)

2. Unmask the rest of the page. Ask for volunteers to read the headline, the text just below it, and the first two paragraphs of the article.

3. Play the video to learn more about a disappearing glacier. Then instruct students to read the rest of the article silently.

4. Turn to page 11 and enlarge the text in the box labeled "What Do You Think?" Have a volunteer read the text. "Eric Guth often puts himself in danger to get good photos of an ice cave. Is the benefit to science worth the risk?"

5. Discuss with your students why they think it is important for scientists to learn more about ice caves. Record their answers on a digital sticky note. Discuss whether the students would be willing to enter dangerous situations for the sake of science.

DISCUSSION

Perform the hands-on activity on page TE 7. Then discuss the students' results. How did snowfall affect how their glacier moved? How does a glacier cause erosion? How do they think this movement might affect the glacier caves?

ASSESSMENT

Go to the online skills sheet database at www.scholastic.com/scienceworld to download the "Glacier Exploration" work sheet, in which students will analyze the diagram of a glacier's anatomy on page 9 of the magazine.

DON'T TEACH EARTH SCIENCE?

Go to www.scholastic.com/scienceworld to download these assessment skills sheets instead:

BIOLOGY: FROZEN IN TIME

The chilly depths of a glacier may also be home to the remains of people, such as the ice mummy discovered in the Italian Alps in 1991. Read this passage about how scientists used medical technology to learn about the life and death of the person.

PHYSICS: COLORS OF LIGHT

Glacier ice caves appear blue because the thick ice filters the red colors out of sunlight. Try this hands-on experiment to see how filters can absorb different colors of the visible light spectrum.

RESOURCES

* VIDEO EXTRA: Watch a video about glaciers at: www.scholastic.com/scienceworld.

* To learn more about how glaciers form and where they are found, and to see many pictures of different glaciers, visit: http://nsidc.org/glaciers.

* Learn the difference between glacier caves and ice caves that form in rock and see pictures of many caves at: http://glaciercaves.com/html/glacie_12.HTM.

DIGITAL ISSUE KEY:

SHOW ALL PAGES

HOME

MASK TOOL

DIGITAL STICKY NOTES

TEXT HIGHLIGHTER

DRAWING TOOL

GAME

POP-UP

VIDEO PLAYER
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Title Annotation:EARTH: GLACIERS; Eric Guth
Author:Adams, Jacqueline
Publication:Science World
Date:Feb 13, 2012
Words:1711
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