Military Geology in a Changing World
William Leith

Those expert at preparing defenses consider it fundamental to rely on the strengths of such obstacles as
mountains, rivers and foothills. They make it possible for the enemy to know where to attack. They secretly

conceal themselves under the nine-layer ground.

Tu Yu, A.D. 735-812

The U.S. military actions in Afghanistan have brought into the American public’s eye the people and place names of Afghanistan, its history, its religions and, not surprisingly, its geology. Geology’s underlying role in recent events is particularly apparent because our adversaries have moved below ground. The military needs “geologic intelligence” on the locations and characteristics of caves, and on how resistant tunnel entrances may be to conventional and penetrating bombs. Geology has become particularly important in the search for Taliban and Al Qaeda forces in Afghanistan, where the U.S. Geological Survey (USGS) estimates there are more than 10,000 caves, both natural and manmade.
For geologists who have worked in the field of military geology, the conflict in Afghanistan and search for Osama bin Laden challenge our abilities to compile, analyze and disseminate to military planners our best interpretations of maps, satellite images and estimated rock properties. We have been called on to apply a wide variety of skills from afar to address the question of where terrorists could hide and how their presence might be detected.

Unique to the search for bin Laden, this challenge has included the analysis of a rock outcrop visible only on videotape. Video is not the kind of material evidence that a forensic geologist would choose for contributing to national security. Yet despite its gross limitations, it provides some information useful for limiting possible search areas. For comparison, consider that few people would have thought that a careful examination of the pebbles used as counterweights in Japanese balloons during World War II could have precisely located the staging areas for Japanese attacks on the United States (such is the story John McPhee documents in his 1998 book, Irons in the Fire).

While this type of forensic work is compelling, military geologists are more often involved in basic studies and compilations of terrain, geology and soils. Military geologists must determine how well troops and vehicles can travel across a landscape. They must identify sources of groundwater, construction material or sites suitable for airfields. Or they must analyze underground rock environments, either for protecting critical military structures and personnel or for targeting weapons. The tool military geologists often use today is remote sensing: they can analyze a terrain’s composition with multispectral or hyperspectral images; or they can determine precise topography by processing the small changes in multiple radar images taken of one location.

From Napoleon to World War II

Geology has supported military activities at least since the time of Napoleon, who included two geologists in his expeditionary forces during his invasion of Egypt in 1798, as told by George Kiersch and James Underwood in their 1998 article, “Military Geology in War and Peace” (Reviews in Engineering Geology, vol. 13).
During the 18th, 19th and much of the 20th centuries, military geology became defined by “terrain intelligence”: basic analysis of terrain for assessing the movement of troops and vehicles; locating access routes; finding staging areas and construction materials; analyzing slope stability and rock excavation characteristics; and mapping surface and subsurface hydrology.

Military geology has played a role from the American Revolutionary War through the Korean War, and has since expanded to include a broad range of disciplines, from geophysics to oceanography to botany. Even as far back as the Civil War, the military used tunnels and other underground excavations in both offensive and defensive applications.

By most accounts, the first to make a large-scale use of geology in military operations were the Russians, who, during the Russo-Japanese war of 1904 to 1905, employed geologists as advisors for constructing fortifications. Also during this war, the Japanese compiled detailed maps of the entire Korean peninsula. American military geologists used these same maps during the Korean War. They remain today the best available comprehensive geologic maps of North Korea.

During World War I, U.S. military geologists working in France compiled the first “engineering geologic maps,” laying out the physical characteristics of surface materials far into enemy territory — essential information for building surface fortifications.

By the Second World War, military geology was a well-developed science. The USGS established a Military Geology Unit in 1942. By the end of the war, the unit employed more than 250 geologists and other professionals, and had offices in Heidelberg and Tokyo. For many years, one of the requirements for USGS military geologists was the ability to work in at least two languages; many could work in six or seven. The unit’s wartime efforts focused on compiling terrain intelligence; determining how well troops and vehicles could move over land; finding water, fuel and mineral resources; finding construction materials and helping to solve construction problems; and siting airfields.

Digging deeper

The Cold War changed the focus of military geology and presented new challenges to military geologists. The development and testing of nuclear weapons required rigorous research into rock properties at high pressures and temperatures, air blast effects on surface materials — such as soil “sweep-up” — and numerous other effects of nuclear weapons on rock, soil and other natural materials.
Military structures moved deep underground. As missile silos and strategic underground command posts were protected, or “hardened,” by increasing depths of rock, the accurate geologic assessment of in-situ rock properties became crucial, both for ensuring the security of our own facilities and for assessing the effectiveness of our nuclear arsenal against foreign, hardened targets.

By the end of the 20th century, the proliferation of underground military facilities located in diverse geologic environments of varying geologic characteristics presented a huge challenge to the U.S. military and, hence, to military geologists. For example, it has been estimated that more than 1,000 underground facilities lie just along the Korean Demilitarized Zone.

The U.S. Secretary of Defense in 1994 released a report that identified technologies for countering threats from nations or terrorist groups armed with weapons of mass destruction. The report identified two goals for military geology: detecting and characterizing underground facilities, and defeating hardened underground targets with non-nuclear weapons. To meet these goals, military geologists use techniques, particularly remote sensing, to find and characterize a foreign underground facility.

Military underground facilities are often built to use topography, geologic structure, and rock depth and hardness as protection.  The military geologist compiles what Thomas Eastler and others in 1998 coined “strategic geologic intelligence,” information for evaluating the vulnerability of these underground facilities. This intelligence includes bedrock geology, weathering and soil development, weight volume, intact mechanical properties, and even data on how projectiles penetrate the rock. A geologist might analyze a rock’s properties in the lab, and then extrapolate how those properties would differ under varying weathering conditions. Some weathered granite in North Korea, for example, can be dug with a shovel, thanks to the extreme weathering it experiences in the rainy climate.

These diverse data are used in calculations and 3-D models that are tools for determining the effects of weapons and the vulnerability of a single tunnel entrance or a broad underground complex, and sometimes even for the development of new weapons.

Geologic research is also useful both for the monitoring and verification of the nuclear test limitation treaties and for ensuring the containment of U.S. underground nuclear tests — how well an underground test site holds in radioactive gas. This work has included not only assessing the geologic conditions at underground nuclear test sites, both U.S. and foreign, but also making the regional geological and geophysical analyses that support accurate location and identification of nuclear tests through their seismic signals.

In recent years, cooperation between the United States and the states of the former Soviet Union has provided valuable ground truth of the remote geologic assessments made over several decades at nuclear test sites, missile silos and other underground facilities. For example, military geologists were considered key personnel on U.S. teams making the first onsite visits to the Soviet and Russian nuclear test sites in eastern Kazakhstan and on the Arctic island of Novaya Zemlya.

In recent years, the USGS Special Geologic Studies Group has tapped the expertise of a wide variety of earth scientists: not only geologists and cartographers, but also seismologists and other geophysicists (support for nuclear test monitoring); paleontologists and petrologists (forensic geology); soil scientists (forensic geology and studying weathered rock properties); engineering geologists, rock mechanicians and statisticians (rock properties and variability); experts in multispectral, hyperspectral and radar remote sensing (site characterization); and computer specialists (geographic information systems, spectral databases, etc.). Computers are an essential tool for mapping, compiling images and statistical data, processing data, modeling and analysis, and communication.

Like all sciences, military geology has benefited, and will continue to benefit, from advances in technology, particularly remote sensing tools and technologies for identifying, evaluating and testing materials. At the same time, advances in underground engineering technologies have allowed the construction of deeper, more complex underground facilities that are difficult for military planners to “hold at risk.” Similarly, advances in the techniques of deception and evasion have made it more challenging to identify and characterize foreign underground construction sites.

And in areas such as eastern Afghanistan, the sheer number of tunnels and caves presents an obstacle to geologists called upon to contribute to the evaluation of weapons effectiveness and targeting. These and related challenges keep the science of military geology a stimulating and constantly changing field; and one that is increasingly relevant to military activities and national security.

Leith was chief of the USGS Military Geology Group from 1990 to 2000. He participated in the renegotiations of the Threshold Test Ban and Peaceful Nuclear Explosions Treaties and was a member of the first U.S. team to travel to a Soviet nuclear test site in 1988. He is now a senior technical advisor at the U.S. Department of State in Washington, D.C.

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