Rocks vs bombs: Fordow & Natanz show how subsurface geology shapes survivality of underground targets

In a world of advanced warfare, the most formidable defence may not lie in steel or secrecy, but in the stone beneath our feet.

Recent reports of targeted airstrikes on Iran’s nuclear infrastructure have revealed an unexpected player in the survival of underground targets: Geology. When the United States deployed its heaviest bunker-busting bomb — the 30,000-pound GBU-57 Massive Ordnance Penetrator (MOP) — the effectiveness of the strike varied not just by engineering, but by rock type.

Two sites in Iran illustrate this dramatically: Fordow and Natanz, both home to uranium enrichment facilities but resting on vastly different geological foundations.

Fortress of carbonate rock

The Fordow Fuel Enrichment Plant, near Qom, lies buried beneath around 80-90 metres of solid limestone and dolostone, formations typical of the Zagros Mountains. These carbonate rocks, formed over millions of years from compressed marine sediments, are dense, layered and mechanically competent. In geological terms, they are adept at dispersing shockwaves and resisting fracturing.

Military analysts suggest that a dozen MOPs were required to even begin penetrating Fordow’s geological shield. The rocks did not merely cover the facility — they became part of its armour.

Soft ground, high impact

In contrast, the Natanz facility rests on alluvial sediments — unconsolidated sands, silts and gravels deposited by ancient rivers. These loose deposits lack the cohesive strength of rock, making them far more susceptible to compression and collapse under explosive force.

Here, just two bombs were enough to inflict major structural damage, according to satellite imagery and regional intelligence. In this case, soft geology became a liability.

These contrasting outcomes underscore a crucial but often overlooked truth: Subsurface geology is not neutral in the context of war or peace. The fields of lithology, stratigraphy and rock mechanics — typically associated with civil engineering or mineral exploration — are now critical in national security planning.

Whether designing nuclear bunkers, underground metros, or missile silos, understanding what lies beneath is as important as what is built above. Dense rocks like granite or dolostone can offer natural protection. Sediments and fractured zones may amplify vulnerabilities. The thickness, layering and moisture content of subsurface formations can all affect how shockwaves travel and dissipate.

Case for geological-defence alliance

As geopolitical tensions push critical infrastructure deeper underground — from data centers and command hubs to strategic reserves and tunnels — the intersection of geology and defence demands greater attention. In many countries, there is growing recognition of the value geologists can bring when involved early in the planning of such facilities, especially to enhance structural safety and long-term sustainability.

India’s growing investment in underground infrastructure — from nuclear storage and military tunnels to metro systems and deep mines — highlights the importance of interdisciplinary collaboration between geologists and planners to ensure long-term safety and strategic resilience.

The takeaways from Fordow and Natanz go beyond Iran. They present a real-world case study of how Earth science is directly linked to human survival and strategic resilience. Geological surveys, 3D subsurface models and rock strength testing can and should be integrated into defence and disaster-resilience planning.

Because, in the end, it may not be reinforced walls that determine survival, but the ancient rock beneath — silent, immovable and shaped by a billion years of Earth’s history.

Nipam Joshi is a geologist and currently serves as assistant mineral economist (intelligence) at the Indian Bureau of Mines, Ministry of Mines, Government of India. Views expressed are the author’s own and don’t necessarily reflect those of Down To Earth.