Fossils and Geological Eras

The Permian-Triassic extinction event is estimated to have caused the extinction of approximately 90% of all marine species and 70% of all terrestrial vertebrate species.

The leading hypothesis for the cause of the Cretaceous-Paleogene extinction event is the impact of a large asteroid or comet in the Gulf of Mexico.

The evolution of humans after the last glacial period is not an example of an adaptive radiation event, as it did not occur after a mass extinction event.

Extinction studies is the term used to describe the study of mass extinctions and their causes.

Developing the ability to fly is not an example of an adaptation that helped species survive the Cretaceous-Paleogene extinction event, as flying animals were already present before the extinction event.

Interglacial period is the term used to describe the period of time between two mass extinction events.

The principle of superposition states that in a sequence of sedimentary rocks, the oldest rocks are at the bottom and the youngest rocks are at the top. This is because sedimentary rocks are formed when sediment is deposited on top of existing rock layers.

Relative dating is the process of determining the relative ages of rocks and fossils based on their position in a stratigraphic sequence. This is done by using the principle of superposition, which states that in a sequence of sedimentary rocks, the oldest rocks are at the bottom and the youngest rocks are at the top.

Absolute dating is the process of determining the absolute age of a rock or fossil using radioactive isotopes. This is done by measuring the amount of a radioactive isotope in a sample and comparing it to the amount of a stable isotope of the same element. The ratio of the radioactive isotope to the stable isotope can be used to calculate the age of the sample.

Index fossils are fossils of organisms that existed for a short period of time and were widely distributed geographically. This makes them useful for determining the relative ages of rocks and fossils. Index fossils are often used to define the boundaries between different geologic periods.

Body fossils are fossils of organisms that are preserved in their entirety. This can include the entire skeleton, or just a part of the organism, such as a leaf or a tooth. Body fossils are often used to study the evolution of organisms and to reconstruct ancient environments.

Trace fossils are fossils of organisms that are formed when an animal or plant leaves a trace of its activity, such as a footprint or a burrow. Trace fossils can be used to study the behavior of ancient organisms and to reconstruct ancient environments.

Coprolites are fossils of animal or plant feces. Coprolites can be used to study the diet of ancient organisms and to reconstruct ancient environments.

The Precambrian is the oldest geologic period, and it lasted from the formation of the Earth to the beginning of the Paleozoic era. The Precambrian is divided into several eons, including the Hadean, Archean, and Proterozoic eons.

The Cenozoic is the youngest geologic period, and it began about 66 million years ago. The Cenozoic is divided into three eras: the Paleogene, Neogene, and Quaternary eras.