The stones of Stonehenge have stood for millennia due to the solid and ingenious construction of the site, combined with an excellent fitting of the stone blocks together and a good distribution of weight to resist external forces.
The stones of Stonehenge are arranged according to a carefully studied geometry, primarily based on circles and arcs. This organization allows the monuments to evenly distribute the weight of each stone, thereby improving their overall stability. The builders used an ingenious system of joints called tenons and mortises: stone projections (tenons) fit directly into the corresponding recesses (mortises) to securely lock the blocks together. This process prevents lateral movement and limits the risk of collapse. Finally, the slight curvature of the horizontal lintels and the precise fitting between them reinforce the cohesion and sturdiness of the whole, keeping the structure intact for millennia.
Stonehenge owes part of its incredible stability to its simple yet effective foundations. The standing stones, known as megaliths, are set in carefully and precisely dug holes. These rather shallow pits are filled and secured with a compacted mix of gravel, broken stones, and crushed chalk, ensuring a solid support for the vertical blocks. This technique stabilizes each stone against lateral movements, without the need for deep foundations. The enormous weight of the vertical and horizontal stones (lintels) also contributes to their stability: the heavier it is, the less it moves easily. After several millennia standing, one can say that these simple little techniques work quite well.
Stonehenge was designed to withstand earthquakes and violent storms thanks to its clever layout. The vertical stones were installed with a slight interlock with those placed horizontally, thereby limiting their risk of falling even in the event of tremors. The choice of large, solid stones also allows them to easily endure strong winds and the rare extreme phenomena that the region may experience. Combined with their massive size and low center of gravity, this trick ensures that these enormous stone blocks hardly move even when facing centuries of harsh weather or occasional tremors.
Stonehenge has withstood the test of time remarkably well, notably because the stones used are extremely resistant to erosion. Their geological composition, especially the hard sandstone (sarsen), easily endures the majority of usual weather conditions such as rain, wind, or even some temperature variations. With the relatively mild weather of England, these megaliths have never experienced conditions extreme enough to truly accelerate their degradation. The vertically erected structure also allows rainwater to flow easily along the surface, thus preventing water from stagnating on the stones and greatly limiting their natural alteration. Moreover, even after several thousand years outdoors, the signs of wear remain minimal and superficial, a testament to extremely slow erosion.
The large upright stones at Stonehenge, called sarsens, mainly come from a hard and durable rock: a type of solid sandstone rich in silica. This material, derived from compacted and naturally cemented sandy deposits over millions of years, is extremely resistant to time and weather.
The smaller stones, the famous bluestones, have a different origin: they are primarily dolerites and rhyolites that come straight from the Preseli Hills in Wales, over 200 kilometers from the site. They contain quite a few crystals and various minerals, which makes them both strong and uniquely beautiful.
These geological features give the stones of Stonehenge a natural robustness that has allowed them to remain in place for a considerable number of millennia.
Stonehenge is not an isolated phenomenon. Indeed, hundreds of other circles that utilize the same architectural principles exist in Great Britain, but many of them are less well preserved or have disappeared over the centuries.
Some of the stones used at Stonehenge come from the Preseli Mountains, located more than 200 kilometers from the site. The ancient builders are believed to have transported these heavy stones on wooden rollers and via waterways, demonstrating remarkable logistical skills for their time.
The heaviest stone that makes up Stonehenge, known as the "Heel Stone," weighs about 30 tons, which is equivalent to five adult elephants!
Archaeological excavations around Stonehenge have revealed primitive tools, such as stone hammers and deer antlers, suggesting how these massive stones were carved and shaped approximately 4,500 years ago.
Although no structure is completely immune to natural threats such as earthquakes or erosion, thanks to the ingenuity of its original design, the robustness of its materials, and modern conservation interventions, Stonehenge remains remarkably stable. The site is continuously monitored to proactively detect any alarming signs of degradation.
Indeed, Stonehenge went through several construction phases that started around 5,000 years ago and spanned nearly a thousand years. The monument we see today is the result of successive additions and modifications made by multiple generations, which partly accounts for its strength and durability over time.
Stonehenge is primarily composed of two types of stones: the locally sourced sarsen sandstone blocks and the bluestones, which originate from the Preseli Hills in Wales, located over 200 km from the site. These stones were chosen for their durability, strength, and unique qualities.
Although the exact method remains unknown, archaeologists believe that the builders of Stonehenge used a clever combination of wooden levers, strong ropes, earthen ramps, and human strength. These techniques, while rudimentary by our standards, were effective enough to precisely assemble large stones weighing several tons.
Stonehenge is distinguished by the impressive size of its megaliths and by a highly sophisticated architecture involving the precise interlocking of uprights and lintels. Unlike other ancient stone circles, which are often simply made up of standing stones, Stonehenge features a complex and sturdy structure that grants it remarkable durability over time.
Yes, several restoration operations were carried out in the 20th century to ensure the site's longevity. Some stones had been shifted or moved over time and were replaced or straightened, while faithfully preserving the original historical appearance of the monument.
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