In Huelgoat, a village in the Finistère region of Brittany, France, the landscape is defined by a striking formation of giant granite boulders scattered in a chaotic pattern. This phenomenon, known as granitic chaos, has long puzzled hikers and scientists. For many years, the prevailing theory suggested that these massive rocks were transported by a vanished glacier or an ancient sea. However, recent geological research has revealed that this explanation is incorrect. Instead, the granite blocks were formed in place through a slow chemical process that occurred millions of years ago, not by glacial or marine activity. The glacial hypothesis was appealing due to the size and rounded shape of the boulders, which resembled those found in glacial deposits. However, the region was never covered by large Quaternary glaciers, and no marine sediments support the idea of an ancient sea. This led geologists to seek a different explanation, one that involved a chemical transformation of the granite itself. Rather than being moved by external forces, the rocks were altered in place through a process known as "onion peeling weathering." This transformation began about 340 million years ago when a large mass of molten rock solidified underground, forming the Huelgoat granite massif. The true change occurred much later, between 60 and 2 million years ago, when the area experienced a humid tropical climate. Rainwater seeped into the cracks of the granite, chemically breaking down the feldspar minerals that make up the rock. Over time, the outer layers of the granite turned into coarse sand, while the inner parts remained hard. This process created isolated granite balls, resembling fruit cores surrounded by soft pulp, embedded in a sandy matrix. Since about 2 million years ago, erosion has gradually removed the surrounding sand, exposing the granite balls and creating the chaotic landscape seen today. Some of the larger rocks, like the famous 137-ton Trembling Rock, have slid slightly downhill due to gravity, gathering in the valley. However, this movement was local and not the result of long-distance transport. The Huelgoat chaos is a testament to a vanished tropical climate, with each granite ball acting as a fossil of a time when the region was much warmer and wetter than it is today. The coarse sand beneath our feet still carries the memory of this ancient, humid past.