Crystals: Mark A. Schneider/Photo Researchers, Inc.
Water Wonders Acid waters may wipe out the smallest animals in Earth's oceans.
On Thin Ice Earth is heating up. That means trouble for animals in the Arctic. Global warming could melt their habitat. Travel to the top of the world on page 10 of our Nov.-Dec. 2007 issue to learn why animals there are on thin ice.
Crystals There is an amazing cave in Mexico. Crystals inside it are as long as telephone poles. How did they get so big? What stories can they tell about Earth? Go rock hunting on page 16 of our Nov.-Dec. 2007 issue.
