Stonehenge stands as a silent testament to the ingenuity and determination of its Neolithic and Bronze Age builders. For millennia, the towering stones on Salisbury Plain have captivated observers, prompting endless questions about their purpose and, perhaps most compellingly, how they were even put there. The construction wasn’t a single event but unfolded over centuries, involving incredible feats of engineering, particularly concerning the two main types of stone used: the smaller bluestones and the colossal sarsens.
Understanding Stonehenge’s construction requires appreciating the sheer scale of the undertaking. This wasn’t merely piling rocks; it was quarrying, transporting, shaping, and erecting massive stones using only rudimentary tools made of stone, wood, and bone. It represents a monumental investment of time, resources, and coordinated labour, hinting at a sophisticated social structure capable of organizing such complex projects.
The Enigma of the Bluestones
The earliest stone elements incorporated into the monument were the bluestones. These igneous rocks, primarily spotted dolerite, rhyolite, and volcanic ash, are noticeably smaller than the later sarsens, typically weighing between 2 and 5 tonnes each. While still substantial, their true marvel lies in their origin. Geological analysis has pinpointed their source to the Preseli Hills in Pembrokeshire, West Wales, a staggering distance of over 240 kilometres (150 miles) from Salisbury Plain.
How these stones made this incredible journey remains one of Stonehenge’s most debated topics. Several theories exist:
- Human Transport (Overland): This theory suggests teams of people dragged the stones on rollers and sledges, possibly using timber trackways over marshy ground. It would have required immense manpower and organization, navigating challenging terrain.
- Human Transport (Sea and River): Another popular hypothesis involves moving the stones by raft along the Welsh coast, potentially up the Bristol Channel, and then hauled overland or navigated further up rivers like the Bristol Avon. This route minimizes the overland distance but introduces maritime challenges.
- Glacial Transport: A less widely accepted theory proposed that glaciers carried the bluestones closer to Salisbury Plain during an earlier ice age, reducing the distance humans needed to move them. However, geological evidence for glacial deposits of bluestone near Stonehenge is sparse.
Regardless of the exact method, moving dozens of multi-tonne stones across such a distance represents an extraordinary logistical feat for a prehistoric society. The motivation behind selecting these specific stones from so far away remains unclear, suggesting they held profound cultural or spiritual significance.
Scientific analysis has confirmed the origin of many Stonehenge bluestones. Geochemical matching links specific stones at the monument to precise outcrops in the Preseli Hills. This provides strong evidence against the theory of purely local glacial transport for the majority of these stones.
Raising the Giants: The Sarsens
The most iconic features of Stonehenge are the massive sarsen stones, forming the outer circle and the inner trilithons (the three-piece structures with two uprights and a lintel). These are gargantuan blocks of silicified sandstone, significantly larger and heavier than the bluestones. The uprights typically weigh around 25 tonnes, while the largest, the Heel Stone, may weigh over 30 tonnes. The lintels add another 6-7 tonnes each.
Quarrying and Transporting Sarsens
Unlike the bluestones, the sarsens had a shorter, though still challenging, journey. Their source is now confidently identified as the Marlborough Downs, around 30 kilometres (20 miles) north of Stonehenge. While closer than Wales, moving these behemoths overland was a Herculean task.
Sarsen stone is incredibly hard. Extracting suitably sized blocks likely involved exploiting natural fissures in the rock, perhaps widened using fire and water, and then hammering away with large stone mauls. Once freed, the blocks needed transporting across the undulating landscape. It’s almost certain that vast teams of people were required, pulling the stones on wooden sledges, possibly running over log rollers laid on prepared trackways. Estimates suggest it could have taken hundreds, perhaps over a thousand, individuals to move a single large sarsen. The route would have been carefully chosen to avoid steep inclines and marshy ground as much as possible.
Shaping and Finishing
One of the most remarkable aspects of the sarsen structures is the level of shaping and finishing applied – unique among British megalithic monuments. The builders weren’t content with simply erecting rough blocks; they meticulously worked the stones.
Using stone mauls, possibly weighing up to 30kg, they pounded the surfaces to create relatively smooth faces and shaped the stones into rectangular forms. The most sophisticated aspect is the use of joinery techniques borrowed from woodworking:
- Mortise and Tenon Joints: Protruding tenons were carved onto the tops of the upright sarsens, which then fitted into corresponding mortise holes cut into the underside of the lintel stones. This locked the lintels securely in place.
- Tongue and Groove Joints: Some lintels in the outer circle were also joined end-to-end using vertical tongue and groove joints, creating a more stable, continuous ring.
This intricate shaping, performed on incredibly hard stone using only stone tools, demonstrates exceptional skill, patience, and planning. It also implies a deep understanding of structural stability.
The Engineering of Erection
Getting the stones to the site was only half the battle; raising them into position was another immense challenge. How did they lift 25-tonne uprights and place 7-tonne lintels nearly 7 meters off the ground?
Raising the Uprights
The most plausible method involves digging a large pit for the base of the stone, with one side sloped to form a ramp. The sarsen would be levered and dragged until its base slid down the ramp into the pit. Once partially upright, teams using ropes made from plant fibres or leather, possibly anchored to timber A-frames, would have pulled the stone fully vertical. The pit would then be backfilled with rubble and compacted to secure the stone.
Placing the Lintels
Lifting the lintels was perhaps even more complex. The prevailing theory suggests the use of timber scaffolding or cribs. Gradually, layers of massive timbers would be built up alongside the uprights. The lintel stone would then be laboriously levered or rolled up successive levels of this platform until it reached the required height. Finally, it would be maneuvered sideways until the mortise holes aligned with the tenons on the uprights, and then carefully lowered into place. This process would have required immense precision and coordination to avoid disaster.
While experimental archaeology provides plausible methods for moving and erecting the stones, we lack direct evidence of the exact techniques used. No remains of large timber structures or sledges have been found, likely due to decay over millennia. Our understanding is based on logical inference, archaeological finds of tools like mauls and antler picks, and the stones themselves.
A Monument to Human Endeavour
The construction of Stonehenge, particularly the handling of the sarsen and bluestone megaliths, remains a profound example of Neolithic and Bronze Age engineering. It required detailed knowledge of materials, sophisticated logistics, immense manpower, and likely generations of effort. The choice of stones from distant locations, the precise shaping and joining techniques, and the sheer scale of the monument speak volumes about the capabilities, beliefs, and social organization of the people who built it. Stonehenge is more than just a circle of stones; it’s a masterpiece of prehistoric architecture and engineering, embodying the enduring human drive to create and leave a mark on the landscape.
