text: Geological Geological SSSI/ASSIs are selected by a different mechanism to biological ones, with a minimalistic system selecting one site for each geological feature in Great Britain. Academic geological specialists have reviewed geological literature, selecting sites within Great Britain of at least national importance for each of the most important features within each geological topic (or block). Each of these sites is described, with most published in the Geological Conservation Review series, and so becomes a GCR site. Almost all GCR sites (but no other sites) are subsequently notified as geological SSSIs, except some that coincide with designated biological SSSI management units. A GCR site may contain features from several different topic blocks, for example a site may contain strata containing vertebrate fossils, insect fossils and plant fossils and it may also be of importance for stratigraphy.
  Geological sites fall into two types, having different conservation priorities: exposure sites, and deposit sites. Exposure sites are where quarries, disused railway cuttings, cliffs or outcrops give access to extensive geological features, such as particular rock layers. If the exposure becomes obscured, the feature could in principle be re-exposed elsewhere. Conservation of these sites usually concentrates on maintenance of access for future study. Deposit sites are features which are limited in extent or physically delicate—for example, they include small lenses of sediment, mine tailings, caves and other landforms. If such features become damaged they cannot be recreated, and conservation usually involves protecting the feature from erosion or other damage.
  Legal status
  Following devolution, legal arrangements for SSSIs (Scotland, England, Wales) and ASSIs (Northern Ireland) differ between the countries of the UK.  The Isle of Man ASSI system is a separate entity.