Avsnitt 19

Most dead animals and plants break up, get decomposed, and become part of the soil, but some turn into fossils. A fossil forms when a plant or animal dies, and gets buried. If conditions are right, water gets into the fossil bed, and chemical reactions preserve the impressions for thousands or millions of years . There are different types of fossils — imprints of animals, black carbon outlines, hardened bones, or actual animals and plants that have been trapped in ice or hardened tree sap.