Representation of time based on the rock record of earth

It is a chronological system that consists of both chronostratigraphy and geochronology

Chronostratigraphy- is the branch of geology that consists with the establishing of the absolute ages of rocks (can also be known as strata)

Geochronology- is the branch of geology that consists of with the dating of rock formations and geological events

The geological time starts begins at the start of the Archean eon (which takes place around 4 billion to 2.5 million years ago)

The geologic time is basically the calendar of the earth’s history events

The geologic time scale consists of eons, eras, periods, epochs, and ages

• Eons are precambrian and phanerozoic

• Eras are paleozoic, mesozoic and cenozoic

• Periods are cambrian, ordovician, silurian, devonian, mississippian, pennsylvanian, permian, triassic, jurassic, cretaceous, paleogene and neogene

• Epoch are paleocene, eocene, oligocene, miocene, pliocene, pleistocene and quaternary

• Ages are danian, selandian, thanetian, ypresian, lutetian, bartonian, bartonian, priabonian, rupelian, chattian, aquitanian, burdigalian, langhian, serravallian, tortonian, messinian, zanclean and placenzian

• The most simple way of dating geological features is to look at the relationship between them

• ‘ principle of inclusions’ states that any rock fragments that are included in rock must be older than the rock in which it is already included

• ‘ principle of cross cutting relationship that states any geological feature that cuts across, or disrupts another feature that must be younger than the feature that is disrupted

• Geologists receive lots of information from fossils

• Fossils have many purposes

• They provide information about the climates at that time, etc but they can also help to date rocks

• If we understand the sequence of evolution on earth, that knowledge can be applied to determining relative ages of rocks

• If geologists can identify the fossil to the species and they know the time period, it most likely that they can determine a range of time of the rocks

• Tree ring dating also known as dendrochronology

• Dating based on the record of reversals of earth’s magnetic field

• Dendrochronology can be applied to dating very young geological materials based on reference records of tree ring growth going back many millenia

• Changes of earth’s magnetic field can be used to date vents in geological history

• Magnetic chronology can be used as a dating method because geologists can measure the magnetic field of rocks using a magnetometer in a lab