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.
