Chocolate Pot (IMAGE) University of Wisconsin-Madison Caption The steamy volcanic vent at Chocolate Pot hot spring in Yellowstone National Park, an iron-rich but relatively cool hot spring where a variety of fascinating microorganisms thrive without oxygen. These microbes respire solid iron much as humans breathe oxygen. Credit Courtesy of Nathaniel W. Fortney Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.