The geological term for a break in the stratigraphic record caused by erosion or non-deposition is an unconformity.
An unconformity marks a period when sediment was not being deposited, or when previously formed rock was exposed and eroded before younger layers accumulated. The missing interval is called a hiatus, so an unconformity represents time absent from the local rock record.
Geologists classify unconformities by the rocks and structures on either side. An angular unconformity has tilted, eroded layers beneath younger strata. A disconformity separates parallel sedimentary layers but records erosion or non-deposition. A nonconformity places sedimentary rock above eroded igneous or metamorphic rock, while a paraconformity lacks an obvious erosional surface.
Scottish geologist James Hutton recognized important examples at Jedburgh in 1787 and Siccar Point in 1788. These outcrops helped demonstrate that Earth’s geological history is vastly longer than a single human lifetime. A common mix-up is treating “hiatus” and “unconformity” as synonyms: the hiatus is the missing time, while the unconformity is the physical boundary or surface recording it.