Like other plants and animals they may require specific living conditions, but they are more abundant and are found in types of sedimentary rocks. Because of this they can be a useful indicator of how climate has changed over a period of time.Earliest appearance in the Cretaceous North Sea
When I finally catch up, she has stopped at a ledge overlooking what our headlamps reveal to be a body of water—one of Dark Star’s many subterranean lakes. She grabs a lanyard attached to her harness and clips it on a gritty attached to a bolt hammered into the rock above us. The rope leads out over the lake and disappears into the black. The setup acts as a sort of zip line to ferry cavers across the frigid lake, too cold to swim in without a wet suit. She gives me a perky smile and steps off the ledge
Photograph by James P. Blair
It&aposs tempting to believe -- as many people do -- that cravings are the body&aposs way of telling us we&aposre lacking a certain nutrient that the food we crave can supply. Chocolate, the belief goes, might soothe a broken heart by replacing compounds lost in oceans of tears. Pregnant women might crave ice cream because they need calcium, or pickles because they lack sodium.Susan Bowerman is a dietitian and assistant director of the UCLA Center for Human Nutrition.