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Chill out! Scientists explore one of the coolest caves on Earth.

Hazel Barton awakens to the sound of a thundering crack. She realizes that the morning sun has warmed the ice near her tent, causing it to split. Barton unzips her tent and steps outside, shivering. She is in Greenland, a large island mostly north of the Arctic Circle where temperatures can plunge to a chilly -40[degrees]Celsius (-40[degrees]Fahrenheit) at night. For Barton--a scientist at Northern Kentucky University--it's a far cry from home.

Why chill out in such a freezing scene? Barton has a cool reason. She's here to explore one of Greenland's many ice caves.

Deep Freeze

About 85 percent of Greenland is coated with moving sheets of ice called glaciers. In summertime, temperatures creep above freezing and melt the top layers of these glaciers. This meltwater flows along the glacier with the force of a raging river. Sometimes, the water flows into cracks in a glacier's ice. As the forceful water pours into the cracks, it carves out caves in the ice.

Barton and her team are about to explore one of these magnificent caves before it disappears. Unlike caves that are carved out of rock and last millions of years, ice caves last only one year. Why? There are two reasons. When air temperatures rise, the ice melts, turning the caves into liquid. Second, as the sun's rays shine down on the glacier throughout the year, they heat the upper layer of ice, but the deeper layers remain unaffected. This difference in temperature within a glacier can cause the ice to split. And when this happens, an ice cave can collapse. Because of these factors, there are only two weeks a year for scientists to explore caves safely. "It has to be warm enough for you to comfortably be in the cave, but cold enough that the caves aren't filled with water," says Barton.

Understanding the risks, Barton and her teammates lower themselves more than 183 meters (600 feet) inside the cave. Once grounded, they notice bands of blue and white along the cave's walls. The white bands are made of packed snow from Greenland's winters. The blue bands are ice that has formed after snow melted in the summertime and refroze.

Cool Discovery

Barton runs her hand along one of these brightly colored walls. She wonders if they contain any organisms. To find out, she pulls an axe from her pack and chips away at a section of the wall. Before making her way out of the cave, she collects several chunks of ice to study.

Back in her tent, Barton melts the ice chunks and examines the water under a microscope. Peering closer, she spots a microscopic insect called a tardigrade. It looks like a six-legged gummy bear!

Tardigrades can survive freezing and thawing, and they can live up to 100 years! Barton and other scientists hope to learn how these animals thrive in such low temperatures.

Dripping Away

To learn more about such organisms, Barton believes that scientists must collect and study as many samples as possible from Greenland's ice caves--before all these frosty structures are gone. What could possibly cause all the ice caves to disappear? According to many scientists, Greenland might not stay frozen forever. They believe that global warming may be increasing Earth's temperatures.

Global warming occurs when gases such as carbon dioxide collect in a planet's atmosphere. This buildup of gases traps the sun's heat on Earth, and the world gets warmer as a result. Eventually, this heat could melt all the ice in Greenland, along with that at the North and South Poles. "There wouldn't be any more ice caves," says Barton.

Scientists are currently looking for ways to stop or slow global warming so that ice in Greenland and other places will stick around far into the future. According to Barton, "When more people start paying attention to global warming, they may find ways to prevent it."

SCIENCE CONTENT STANDARDS

For Grades K-4

* Changes in earth and sky

* Science as a human endeavor

For Grades 5-8

* Structure of the earth system

* Science as a human endeavor

INTEGRATE YOUR CURRICULUM!

Language Arts--Reading Comprehension

BEFORE READING

Set a Purpose

To learn how ice caves form and how and why scientists explore them.

Background

* The National Science Foundation's Arctic System Science Committee recently issued a report stating the rate of ice melting in the Arctic is increasing, which could lead to summertime ice-free ocean conditions within a century.

* Tardigrades--also known as water bears--can live in droplets of water on plants. If the water they live in evaporates, they lose water too and go into a deep sleep. A little water is all it takes for them to spring back to life.

Discussion Questions

* Why do you think scientists study ice caves? (Possible answers: to learn how the caves form; to learn if any organisms live in the caves.)

* Pretend that you are a scientist who is about to study an ice cave. What would you bring with you? (Possible answers: a warm jacket; special shoes to help walk across the ice; a flashlight; an ax or ice pick.)

AFTER READING

Discussion Questions

* What do you think are some qualities that a scientist who explores ice caves must have? (Possible answers: brave; daring; not afraid of heights; likes the cold.)

* Suppose you lived in a town near a glacier. What concerns would you have about rising temperatures? (Possible answers: Rising temperatures could melt the glacier, causing the town to flood; a melting glacier could slide into the town.)

RESOURCES

* Exploring Coves: Journeys into the Earth by Nancy Holler Aulenbach and Hazel A. Barton (National Geographic Society, 2001) follows scientists as they explore amazing caves in Greenland and elsewhere.

* www.pbs.org/wgbh/novo/mtblanc/This NOVA Web site discusses ice caves in France and offers information about what it takes to be an ice-caver.

Words to Know

Glacier--a large sheet of ice flowing very slowly through a valley or spreading outward from a region

Meltwater--water that comes from melting snow or ice

Global warming--an increase in Earth's average temperature over time

Carbon dioxide--a colorless, odorless gas that is present in the layers of Earth's atmosphere

Atmosphere--layers of gas that surround a planet

No-Sweat Bubble Test: (reading comprehension)

DIRECTIONS: Read each question below, and then use the article "Chili Out!" (pp. 12-14) to determine the best answer. Fill in the correct bubble completely.
1. About how much of Greenland is covered
with glaciers?

(A) 25 percent    (C) 75 percent
(B) 50 percent    (D) 85 percent

2. In which country would you not expect to
find an ice cave?

(A) New Zealand   (C) Norway
(B) Mexico        (D) United States

3. Why are ice caves only temporary?

(A) A difference in temperature within
a glacier's ice can cause the cave to
collapse.

(B)  Rising temperatures cause the ice
to melt.

(C) Organisms living inside the cave
walls feed on the ice.

(D) Both A and B

4. How are ice caves formed?

(A) They are carved out by meltwater.

(B) Scientists drill holes into the ice.

(C) Mineral-rich groundwater dissolves
the ice.

(D) Rocks inside the glacier cause the
ice to expand and become hollow.

5. Which of the following statements is NOT
true?

(A) Many scientists believe that global
warming may be increasing Earth's
temperatures.

(B) Hazel Barton discovered an
organism in the ice.

(C) The blue bands along the cave walls
are made of packed snow.

(D) Tardigrades can live up to 100 years.

6. How long do scientists have to explore an
ice cave?

(A) one day       (C) three months
(B) two weeks     (D) one year

7. What is the main idea of this article?

(A) Hazel Barton likes to camp out in
the cold.

(B) Global warming could melt all the
ice in the world.

(C) Scientists explore an ice cave in
Greenland.

(D) Tardigrades live in the walls of ice
caves.


1. D 2. B 3. D 4. A 5. C 6. B 7. C
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Title Annotation:earth science
Author:Brownlee, Christen
Publication:SuperScience
Geographic Code:1GREE
Date:Feb 1, 2006
Words:1327
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