They are engaged in defining the stages of hominid evolution and their artifactual record, and the assignment of a chronology to these stages.
In fact, sedimentary rocks are, in a sense, trash from the Earth's surface deposited in basins.
Although the types of trash in each pit is quite variable, each layer has a distinctive kind of trash that distinguishes it from other layers in the pits.
Principles of Stratigraphy Stratigraphy is the study of strata (sedimentary layers) in the Earth's crust.
Prior to the late 17th century, geologic time was thought to be the same as historical time.
Archbishop James Ussher of Armagh, Ireland, 1654, added up generations from the Old Testament and determined that Earth formed on October 23, 4004 BCE.