Fossils & Radiometric Dating

Let's take a look at fossils. Fossils are the preservation of remains, or traces of remains, of ancient organisms. Like dinosaurs and large birds/reptiles. For an organism to be fossilized, the remains usually need to be covered by sediment soon after death. Sediment can include sandy seafloor, lava, and even sticky tar. Over time, minerals in the sediment seep into the remains. The remains become fossilized. Fossilization usually occurs in organisms with hard, bony body parts, such as skeletons, teeth, or shells. There are multiple types of fossilization, but here are the main four that we use in society today.

Types of Fossilization:

Pre-Mineralization: a process of fossilization of bones, teeth, and tissue in which mineral deposits form internal casts of organisms.

Trace Fossils: evidence of animals being there, but not organic materials.

Casts/Molds: the sediment packs around the fossil, forming an impression. fossil itself dissolves and a hole is left where they were that another sediment forms inside and leaves the impression and now a "mold" of the organism.

Amber: tree sap catches an organism, is trapped and entombed within it. Over time, sap goes through lithification and instead of tree sap, becomes amber.

Soft Tissue: blood samples, collagen, etc.

Radiometric Dating

Radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed.

The difference between relative and radioactive dating is that relative dating determines the relative age of rock layers according to their relative depth. However, radiometric dating determines the absolute age with the use of decaying products of the natural radioactive isotopes.

Relative dating and radioactive dating are two methods in archaeology to determine the age of fossils and rocks. The study of fossils is important for the determination of the kind of organism it represents, how the organism lived, and how it was preserved on the Earth's surface over the past 4.6 billion years.

• Fossils - National Geographic

• Fossil Activities - Fantastic Fun & Learning