Presentation on theme: "Fossils can form in several ways."— Presentation transcript:
1KEY CONCEPT Specific environmental conditions are necessary in order for fossils to form.
2Fossils can form in several ways. Permineralization occurs when minerals carried by water are deposited around a hard structure.
3A natural cast forms when flowing water removes all of the original tissue, leaving an impression.
4Trace fossils record the activity of an organism.
5Amber-preserved fossils are organisms that become trapped in tree resin that hardens after the tree is buried.
6Preserved remains form when an entire organism becomes encased in material such as ice.
7Specific conditions are needed for fossilization. Only a tiny percentage of living things became fossils.
8Radiometric dating provides an accurate way to estimate the age of fossils. Relative dating estimates the time during which an organism lived.It compares the placement of fossils in layers of rock.Scientists infer the order in which species existed.
9Radiometric dating uses decay of unstable isotopes. Isotopes are atoms of an element that differ in their number of neutrons.neutronsprotrons
10Radiometric dating uses decay of unstable isotopes. Isotopes are atoms of an element that differ in their number of neutrons.A half-life is the amount of time it takes for half of the isotope to decay.
11KEY CONCEPT The geologic time scale divides Earth’s history based on major past events.
12Index fossils are another tool to determine the age of rock layers. Index fossils can provide the relative age of a rock layer.existed only during specific spans of timeoccurred in large geographic areasIndex fossils include fusulinids and trilobites.
13The geologic time scale organizes Earth’s history. The history of Earth is represented in the geologic time scale.10025055010002000PRECAMBRIAN TIMECyanobacteriaThis time span makes up the vast majority of Earth’s history. It includes the oldest known rocks and fossils, the origin of eukaryotes, and the oldest animal fossils.
14Eras last tens to hundreds of millions of years. consist of two or more periodsthree eras: Cenozoic, Mesozoic, Paleozoic
15Periods last tens of millions of years. most commonly used units of time on time scaleassociated with rock systems.Epochs last several million years.