Archaeologists working in a volcanic field in northern Saudi Arabia have recovered human bones, stone tools, and charcoal from inside a lava tube that served as an underground refuge for thousands of years. The site, known as Umm Jirsan, represents the first documented case of human occupation inside a lava tube anywhere on the Arabian Peninsula. What makes this discovery especially striking is not just the artifacts themselves but the pattern they reveal: people returned to this dark, subterranean passage again and again across millennia, raising hard questions about why this particular tunnel held such lasting significance for ancient populations moving through one of the harshest environments on Earth.
Situated in a landscape of black basalt and dormant cones, Umm Jirsan forces a reconsideration of how humans adapted to volcanic terrains that were long assumed to be marginal or even hostile. Instead of treating the lava field as a void between more hospitable zones, the evidence suggests that ancient people integrated this underground shelter into broader patterns of mobility, subsistence, and perhaps even ritual. The lava tube was not just a place to get out of the sun; it appears to have been a recurrent waypoint woven into the rhythms of life in northern Arabia over roughly ten millennia.
Inside a Volcanic Tunnel North of Medina
Umm Jirsan sits within Harrat Khaybar, a sprawling basaltic lava field located approximately 125 kilometers north of Medina in Saudi Arabia. Lava tubes form when the outer surface of a flowing lava stream cools and hardens while molten rock continues to drain beneath, leaving behind hollow tunnels that can extend for hundreds of meters or more. These natural corridors offer stable temperatures and protection from wind and sandstorms, making them attractive shelters in regions where surface conditions swing between extreme heat and cold. The Harrat Khaybar field is one of the largest volcanic provinces in the region, and Umm Jirsan appears to be its most archaeologically significant feature identified so far.
What distinguishes this site from other cave discoveries in the Middle East is context. Most known occupation caves in the Arabian Peninsula are limestone or sandstone formations, often associated with springs or cliff faces. Lava tubes have largely been overlooked by archaeologists, partly because they are harder to survey and partly because jagged volcanic terrain discourages modern access and settlement. The fact that people not only entered Umm Jirsan but left behind clear signs of repeated activity suggests the tube offered something rare in this environment: reliable shelter along routes that connected distant communities. The surrounding volcanic landscape, while forbidding, may have funneled pastoral and trade movement through predictable corridors, making the tube a logical and perhaps indispensable waypoint.
Bones, Obsidian, and Charcoal Deep Underground
A peer-reviewed excavation report published in the PLOS ONE study documents the recovery of human remains from within Umm Jirsan, alongside lithics, obsidian knapping debris, and charcoal. The stone tool assemblage is particularly telling. Obsidian, a volcanic glass prized for its sharp edges, does not occur uniformly across the Arabian Peninsula, so the presence of knapping debris—the waste flakes produced when shaping stone tools—indicates that people were actively working imported raw material inside the tube. This was not a place where someone merely took shelter and left a few discarded objects; it was a setting where individuals or groups stayed long enough to manufacture tools and perhaps repair equipment needed for onward travel.
The charcoal deposits point to controlled fire use underground, which carries its own implications for how well people understood the cave’s microenvironment. Lighting fires inside a lava tube requires managing smoke in a confined space, suggesting the occupants learned to select locations with sufficient ventilation, likely near openings or sections where the ceiling rises. The human bones raise additional questions. Whether these remains represent deliberate burials, accidental deaths, or individuals who died during shelter stays is not yet fully resolved by the available evidence. The published study notes that the broader occupation sequence spans several thousand years, but without specific radiocarbon dates for each skeleton, the exact age and cultural context of the individuals remain open questions.
Rock Art and Signs of Repeated Return
Beyond the tube itself, the research team documented rock art panels in the area surrounding Umm Jirsan, adding a cultural and symbolic layer to what might otherwise be interpreted as a purely functional refuge. Rock art in the Arabian Peninsula often depicts animals, human figures, and abstract symbols tied to pastoral life, hunting scenes, and social display. Its presence near a lava tube suggests the site held meaning beyond simple convenience. People marked this place in ways that would be visible to others, perhaps signaling ownership of nearby pastures, commemorating gatherings, or encoding stories about journeys and hardships survived in the volcanic field.
The pattern of evidence—tools manufactured on site, fires lit underground, art created nearby, and human remains deposited within—points strongly toward episodic use over long periods rather than a single occupation event. Reporting in coverage by Nature frames the site as a refuge where humans and their livestock sheltered for roughly 10,000 years, a span that aligns with the multi-layered archaeological deposits described in the primary study. Yet this long chronology also highlights a key uncertainty: without tight radiocarbon sequences for every stratum, the exact rhythm of occupation remains approximate. It is unclear whether people visited the tube every season, every few generations, or primarily during episodes of climate stress such as droughts. The current evidence can demonstrate recurrence but not its precise frequency.
Why a Lava Tube and Not Open Ground
The Umm Jirsan discovery has broad implications for how archaeologists think about mobility and decision-making among ancient pastoral groups in Arabia. For decades, the dominant assumption has been that caves and rock shelters in sedimentary geology—often associated with water sources—were the primary refuges for mobile populations, while volcanic landscapes were treated as marginal. Umm Jirsan challenges that view by demonstrating that lava tubes could provide durable, predictable shelter in otherwise exposed terrain. If other tubes within Harrat Khaybar and comparable volcanic fields were also used, then existing models of migration, herding routes, and trade across the peninsula may be missing key nodes in a subterranean network of stopovers.
One hypothesis worth testing is whether Umm Jirsan functioned as a convergence point for multiple groups rather than a single community’s seasonal stop. Strontium isotope analysis of the recovered human and animal teeth could reveal whether the individuals buried or deposited in the tube came from diverse geographic origins. If the isotopic signatures vary widely, it would suggest the tube attracted people from across the region, functioning more like a crossroads than a private camp. Conversely, a narrow range of signatures might indicate a more localized user group with a stable territory. Either outcome would significantly refine how researchers model pastoral routes through volcanic terrain and could prompt systematic surveys of lava tubes across the wider Arabian Peninsula to see whether Umm Jirsan was unique or part of a broader pattern.
What Remains Uncertain and What Comes Next
For all its significance, the Umm Jirsan study leaves several threads unresolved. The livestock evidence referenced in broader coverage is not yet fully detailed in the excavation report, which means researchers still cannot say with confidence whether the animals sheltered here were primarily goats, sheep, cattle, or a mixture. That distinction matters because different livestock species imply different pastoral strategies, seasonal ranges, and social organization. Goats and sheep, for example, tolerate rugged terrain and can be herded over long distances, while cattle typically require more reliable water and grazing. Clarifying which animals passed through Umm Jirsan would help determine whether the tube lay along local herding circuits or on longer-distance transhumance and trade routes.
Chronology is another major gap. While the stratigraphy and artifacts point to repeated use over thousands of years, the absence of published radiocarbon dates for the human bones means the skeletal remains cannot yet be slotted precisely into the site’s occupational sequence. Future work that directly dates these bones, along with associated charcoal, would sharpen the timeline and clarify whether particular phases of intense use coincide with known climatic shifts in Arabia. Additional excavations could also explore untested sections of the tube, where undisturbed deposits might preserve hearths, plant remains, or further burials. As those data accumulate, Umm Jirsan is likely to shift from being a singular curiosity—a lava tube with bones and tools—into a key reference point for understanding how ancient people navigated, survived, and perhaps even found meaning in one of the most dramatic volcanic landscapes on the Arabian Peninsula.
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*This article was researched with the help of AI, with human editors creating the final content.
