Ussher chronology in the context of "Primate of All Ireland"

Flood geology (also creation geology or diluvial geology) is a pseudoscientific attempt to interpret and reconcile geological features of the Earth in accordance with a literal belief in the Genesis flood narrative, the flood myth in the Hebrew Bible. In the early 19th century, diluvial geologists hypothesized that specific surface features provided evidence of a worldwide flood which had followed earlier geological eras; after further investigation they agreed that these features resulted from local floods or from glaciers. In the 20th century, young-Earth creationists revived flood geology as an overarching concept in their opposition to evolution, assuming a recent six-day Creation and cataclysmic geological changes during the biblical flood, and incorporating creationist explanations of the sequences of rock strata.

In the early stages of development of the science of geology, fossils were interpreted as evidence of past flooding. The "theories of the Earth" of the 17th century proposed mechanisms based on natural laws, within a timescale set by the Ussher chronology. As modern geology developed, geologists found evidence of an ancient Earth and evidence inconsistent with the notion that the Earth had developed in a series of cataclysms, like the Genesis flood. In early 19th-century Britain, "diluvialism" attributed landforms and surface features (such as beds of gravel and erratic boulders) to the destructive effects of this supposed global deluge, but by 1830 geologists increasingly found that the evidence supported only relatively local floods. So-called scriptural geologists attempted to give primacy to literal biblical explanations, but they lacked a background in geology and were marginalised by the scientific community, as well as having little influence in the churches.

James Ussher (or Usher; 4 January 1581 – 21 March 1656) was the Church of Ireland Archbishop of Armagh and Primate of All Ireland between 1625 and 1656. He was a prolific Irish scholar and church leader, who today is most famous for his identification of the genuine letters of the church father, Ignatius of Antioch, and for his chronology that sought to establish the time and date of the creation as "the entrance of the night preceding the 23rd day of October ... the year before Christ 4004"; that is, around 6 pm on 22 October 4004 BC, per the proleptic Julian calendar.