Go Home U.S. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY Antarctic Ice Sheet Computer animations and paper model By Tau Rho Alpha, and Alan K. Cooper Open-file Report 98-353 fl This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this program has been used by the U.S. Geological Survey, no warranty, expressed or implied, is made by the USGS as to the accuracy and functioning of the program and related program material, nor shall the fact of distribution constitute any such warranty, and no responsibility is assumed by the USGS in connection therewith. U.S. Geological Survey Menlo Park, CA 94025 Comments encouraged [email protected] [email protected] 1998 (go backward) <T"1 L^ (go forward) Description of Report This report illustrates, through computer animation and a paper model, why there are changes on the ice sheet that covers the Antarctica continent. By studying the animations and the paper model, students will better understand the evolution of the Antarctic ice sheet. Included in the paper and diskette versions of this report are templates for making a papetfttiodel, instructions for its assembly, and a discussion of development of the Antarctic ice sheet. In addition, the diskette version includes a animation of how Antarctica and its ice cover changes through time. Many people provided help and encouragement in the development of this HyperCard stack, particularly Page Mosier, Sue Priest and Art Ford. This report was enhanced by reviews from Bonnie Murchey, Peter Stauffer and Stephen Eittreim. Table of Contents for paper version of this report. Title page page 1 Description of report page 2 Teachers guide page 4 Paper model of Antarctica page 35 (go backward) <J (go forward) Description of Report Requirements for using the diskette version are: Apple Computer, Inc., HyperCard 2.2 software and an Apple Macintosh computer with an internal disk drive. If you are using System 7, we recommend having at least 8 MB of physical RAM with 4.5MB of memory available for HyperCard. The animation is accompanied by sound. If no sound is heard, change the memory of HyperCard to 4500K and ensure that the control panel "Sound," which is in the "Control Panels" folder under the "Apple" menu, has the volume set to at least 2. To change the memory available to HyperCard, quit this stack. Highlight the HyperCard program icon and choose "Get Info" from the File Menu. Change the "memory requirements" to 4500K and start this stack again. Purchasers of the diskette version of this report, which includes all of the text and graphics, can use HyperCard 2.2 software (not supplied) to change the model (by adding patterns, symbols, colors, etc.) or to transfer the model to other graphics software packages. To see the entire page (card size: MacPaint), select "Scroll" from the "Go" menu and move the hand pointer in the scroll window. If you are experiencing trouble with user-level buttons, select "message" from the "Go" menu. Type "magic" in the message box and press return. Three more user-level buttons should appear. The date of this Open File Report is 6/30/1998. OF 98-353-A, paper copy, 49p.; OF 98-353-B, 3.5-in. Macintosh 1.4-MB high-density diskette. To order this report, contact: USGS ESIC Open-File Report Section, Box 25286, MS 517, Denver Federal Center, Denver, CO 80225-0046 or call (303) 236-4476. These stacks (reports) can be down loaded from self-extracting archives, that are on the U.S. Geological Survey's Learning Web site. The address is: < http://ww^^^gs.gov^ducation/animations/ > [ Back to table of contents ) Teachers Guide: Page 1 of 31 Learn about Antarctica Antarctica lies at the "bottom of the world" and is the highest (in elevation), driest, and coldest continent on earth. It is nearly one and a half times larger than the continental United States, and its coastlines are longer than those that surround North America. The continent is surrounded by the largest of all the oceans - the Southern Ocean - that includes parts of the Atlantic, Pacific, and Indian Oceans. Yet, Antarctica has not always been this way, and at one time it was a more hospitable place. In the following descriptions, you will discover how Antarctica evolved from a giant land mass called Gondwanaland to a continent surrounded by water and covered by ice. And, you will learn how the massive ice sheet that now covers Antarctica evolved, and how the ice sheet acts as the "Earth's refrigerator" to strongly control our global climate and sea level. Antarctica is a remote continent of great beauty and is a challenge to adventurous explorers and scientists who want to know more about "The Last Place on Earth". The Great Southern Continent Antarctica is a vast continent that lies below an even larger "slab" of ice called the Antarctic Ice Sheet. When we look at maps, we see mostly the outline of the edges of the Ice Sheet. But, when we lift up the ice sheet (as you can do with the paper model that comes with this report), we see that there is water and land beneath the ice. There are large seaways and bays that go far into the continent and lie below sea level. And, there are large isolated lakes. Mountain ranges also lie under the ice. They are as long and high as those that cross the western United States. All that we know about what lies under the ice comes from remote sensing "radar" surveys that have been done by scientists from many countries. These surveys cover only a very small part of Antarctica, and there are many surprises yet to be discovered under areas of the ice sheet that have not been studied. But, in general, the continent under the ice is much like any other land areas without ice. [ Back to table of contents j 4 Teachers Guide: O Page 2 of 31 Index map of Antarctica 30° W. 30° E. South America 60° E. L 90° W. 90° E. Australia 120° E. 120° W. 150°W. 150° E. 180C Figure 1. A view of the South Pole and an Index map of Antarctica, showing the relationship of South America, New Zealand and Australia. Teachers Guide: \^] Page 3 of 31 Relative size of Antarctica and the Continental United States 0 1,000 2,000 Km 1,000 2,000 Statute Miles Figure 2. Relative size of Antarctica and the continental United States. Antarctica is estimated to have a surface area of 5,500,000 square miles and the continental United States 3,022,387 square miles. The lines of longitude and latitude that make up the graticule locate only Antarctica. Teachers Guide: Page 4 of 31 Atlantic Ocean Antarctica Weddell Indian Ocean ^V Gambursev . subglacial (under the ice) ^ - Mountains East .«^ ^° Antarctica Antarctica Pacific Ocean Boundary between East and West Antarctica Arrovs indicate ice-flov directions Figure 3. Index map of Antarctica today showing features and ice-flow directions for the Antarctic Ice Sheet. Teachers Guide: Page 5 of 31 Deep oceans surround Antarctica today, but 180 million years ago, the Antarctic land mass was at the center of a super-continent called Gondwanaland. The super-continent was pulled apart into many pieces by the processes of sea-floor spreading. Over the last 175 million years, Antarctica has remained near the south pole while the other pieces of Gondwanaland moved north to become the continents and land masses that we now know of as Africa, India, Madagascar, Australia, New Zealand, and South America. The areas between the land masses became great ocean basins. Antarctica has been in its position at the "bottom of the world" for about the last 100 million years. See Figure 1. The Great Ice Sheets Antarctica has not always been covered by ice. In fact, until 45-50 million years ago, there was little, if any, glacier ice in Antarctica. The climate was temperate and warm, and there were lush forests. We know this from examining rocks from some of the few areas on Antarctica that are not covered by ice in Antarctica. Today, only 2% of Antarctica's land mass is exposed, with the rest under ice. We also have sedimentary rock samples from drilling operations done by ships in the oceans around Antarctica. The rocks.contain information such as fossils, oxygen isotopes, clay minerals, and ice-rafted debris that we can use to piece together what the climates were like and how much of Antarctica was covered by glaciers. The evidence indicates that the first of many large ice sheets of the Cenozoic glacial era began to grow between 36-45 million years ago. Teachers Guide: Page 6 of 31 Ice sheets are composed of snow from frozen fresh water. In fact, the Antarctic Ice Sheet currently holds 68% of the world's fresh water. Where does all this water come from? The answer lies in how ice sheets grow. Many times in the past,however, enormous ice sheets have covered large parts of the Northern Hemisphere, including Greenland, Scandinavia, northern Russia, and North America, as well as Antarctica. Today the ice sheets are smaller, and only exist on Greenland and Antarctica. Before describing the history of the Antarctic Ice Sheet, let us learn a bit more about other great ice sheets and how and why they get thicker or "grow". The last glacial period was at its maximum about 20,000 years ago.