Abstract Potential military applications of geology became apparent in Europe by the late eighteenth century, notably to Napoleon Bonaparte. In the United Kingdom, nineteenth-century practice was commonly to teach elementary geology to army officer cadets, and in twentieth-century conflicts to deploy a single uniformed geologist as a staff officer within each major regional headquarters, initially leaving terrain analysis to geographers. In Germany, considerably greater use was made of uniformed geologists serving as teams within all theaters of military operation in both world wars, generating a wealth of data now published or accessible in national archives. In the United States, a few military geologists were appointed to serve in uniform in France during World War I, but during World War II, a far greater number were civilians, based within a Military Geology Unit of the U.S. Geological Survey at Washington, D.C. Despite different organizational backgrounds, and irrespective of nationality, military geologists have addressed similar geoscience problems.

Abstract Throughout history, if generally more conspicuously in the Old World than the New, military activities have locally and sometimes regionally shaped the face of the Earth by construction of defense works in earth or stone. Military enhancement of terrain features by fortification, scarping, or flooding to form obstacles that counter or deflect attack may thus complement the effects of natural geomorphologic agents. Military operations and exercises have polluted parts of the Earth's surface through use of explosive ordnance and by fuel leakage, and disfigured it by redundant construction works. German military geologists in particular have necessarily developed peacetime roles to protect the environment rather than the state. Yet because agricultural use and urban sprawl are restricted within the large tracts of countryside designated as military training areas, these may preserve a heritage of habitats in a fairly natural state—as valuable in terms of conservation as the many sites worldwide now preserved for their military historical record.

Abstract The 6 km 2 peninsula of Gibraltar is unusual hydrogeologically as, in effect, a small but high limestone island, subject to a Mediterranean climate of cool wet winters and warm dry summers. Provision of an adequate water supply for its town and garrison has been a continuing problem, particularly as the population has grown from about 3000 in the 18th century to over 30 000 by the end of the 20th. The narrow peninsula is dominated by the Rock, a mass of Lower Jurassic dolomite and limestone whose main ridge has peaks over 400 m high. Early supplies of potable water were from roof and slope rainwater runoff, and from shallow wells in the Quaternary sands that cover ‘shales’ flanking the Rock at low levels. Intermittent hydrogeological studies through the 19th and 20th centuries, notably in association with the British Geological Survey in 1876, 1943–1952, and 1974–1985 attempted to develop inferred groundwater resources within the sandy isthmus which links the Rock to southern Spain and in the Rock itself. Problems resulted from inadequate understanding of the geology, of recharge, of the behaviour of aquifers containing saline water at depth and of the need to protect aquifers from pollution. Failure to extract adequate groundwater led to development of a separate supply of saline sanitary water to reduce demand for potable water and innovative attempts to improve slope catchment of rainwater, before near-total commitment to desalination for potable supplies in 1993.

Abstract The 400-m-high Rock of Gibraltar is a partly overturned klippe of Early Jurassic dolomitic limestone, notched by raised shorelines and flanked by Quaternary scree breccias and windblown sands. It dominates a narrow 5-km-long peninsula jutting south from Spain at the western entrance to the Mediterranean Sea. Fortified from at least 1160 to World War II successively by the Moors, Spanish, and British, and subjected to 15 major sieges between 1309 and the Cold War of 1947 to 1989, Gibraltar is arguably one of the most densely fortified and fought over places in Europe. Stone walls, bastions, and numerous artillery positions built to enhance the natural defenses of the coastal cliffs now provide a tourist attraction, but constrain development of the modern city. Occasional rockfalls and the need for slope-safety measures are continuing concerns, especially in areas of scree breccia quarried to provide fill for the extension of a Royal Navy harbor between 1893 and 1905 and a Royal Air Force airfield largely between 1941 and 1943. Water supply has posed a problem throughout the history of the fortress, leading to innovative development of rainwater catchment areas on natural slopes, dual potable/sanitary water supplies, and projects to enhance these by cloud condensation or groundwater abstraction, before near total commitment to desalination from 1993. Tunnels and underground chambers are major features of the Rock. Mostly excavated in five phases between 1782 and 1968 to provide access, reservoirs, accommodation, or storage, they now total over 50 km in length, generally unlined. Tunnel integrity is dependent on excavation technique and bedrock characteristics. From the early eighteenth century to recent years, much of the major construction work on Gibraltar was directed and often carried out by Royal Engineers. In 1994, disbandment of 1st (Fortress) Specialist Team RE brought over two centuries of British military engineering on the Rock to an end—and provided a legacy of works and land now largely inherited by civilian bodies responsible to the Gibraltar government.