Ch.3, Sec.4 – Looking at Fossils Fossilized Organisms - the remains of an organism preserved by geologic processes is called a fossil - fossils are usually found in sedimentary rock, but can be found in many types of materials - fossils found in rocks are usually made of bones or shells

Ch.3, Sec.4 – Looking at Fossils - fossils (insects, frogs, lizards) have been found in amber, which is hardened tree sap - fossils can also be preserved through petrification, in which minerals replace an organism’s tissues

Ch.3, Sec.4 – Looking at Fossils - fossils (woolly mammoths, saber-toothed cats) have been found in asphalt pits (evaporating oil), which can trap animals in them - the La Brea asphalt pits in Los Angeles have trapped animals for the last 38,000 years!

Ch.3, Sec.4 – Looking at Fossils La Brea Asphalt Pits, Los Angeles, California

Ch.3, Sec.4 – Looking at Fossils - fossils can also be preserved by frozen climates with tundra - scientists have discovered multiple woolly mammoths in the permafrost tundra of Siberia, in Russia

Ch.3, Sec.4 – Looking at Fossils Other Types of Fossils - any naturally preserved evidence of animal activity is called a trace fossil - trace fossils can be tracks, burrows, or animal dung (coprolite)

Ch.3, Sec.4 – Looking at Fossils - fossils can also be preserved in molds & casts - a cavity in rock where a plant or animal was buried is called a mold - a cast is an object created when sediment fills a mold and becomes rock

Ch.3, Sec.4 – Looking at Fossils Using Fossils to Interpret the Past - unfortunately, the fossil record is incomplete because most organisms never became fossils or haven’t been discovered - using the fossils of plant and land animals allows scientists to reconstruct past climates - some of the oldest fossils in the world have been discovered at the Burgess Shale Formation in British Columbia, Canada

Ch.3, Sec.4 – Looking at Fossils Using Fossils to Date Rocks - many fossils are only found in certain layers of rocks, so dating the rocks give us an idea of how old they are - index fossils are fossils of organisms that lived during a relatively short, well-defined geologic time span - two perfect examples of index fossils are ammonites & trilobites, which is Ohio’s state fossil Ammonites Trilobites

Ch.3, Sec.4 – Looking at Fossils