A theater of ice
The Gavarnie Cirque is a massive natural amphitheater in the Pyrenees mountains, formed by repeated glacial erosion over millions of years. Its near-vertical limestone walls rise up to 1,500 meters (4,900 feet) from the cirque floor to the surrounding peaks, which exceed 3,000 meters in elevation. The structure is immense, measuring about 3,000 meters (9,800 feet) wide at the top and 800 meters wide at its deepest point. The entire circumference of the upper rim spans approximately 6.5 kilometers. This landscape is a direct result of Quaternary glaciers that once grew up to 400 meters deep and extended 40 kilometers to the location of modern-day Lourdes.
The process that formed the cirque is an example of glacial quarrying and abrasion. A mountain glacier, originating in a small depression, plucks rocks from the back wall and grinds the base through the movement of embedded debris. Over successive ice ages, this action carves out a deep, bowl-shaped basin with steep headwalls. The peaks framing the cirque, such as Pic du Marboré (3,248m) and Taillon (3,144m), mark the upper limits of this glacial sculpting. The site, along with the surrounding Pyrénées-Mont Perdu area, was inscribed as a UNESCO World Heritage site in 1997 for its exceptional geological and cultural value.
Hanging valleys and meltwater falls
The largest feature of the cirque is the Grande Cascade de Gavarnie, one of the highest waterfalls in Europe. It has a total drop of 422 meters (1,385 feet), with its single tallest plunge measuring 281 meters. The waterfall is an example of a cataract originating from a hanging valley. The main glacier that carved the Gavarnie valley was much larger and more powerful than the smaller tributary glacier that fed into it from the side. The main glacier eroded its valley floor to a much greater depth. When the glaciers retreated, the tributary valley was left "hanging" at a higher elevation, creating a sheer drop for its meltwater.
The water source for the falls is primarily melting snow and a small glacier located on the Spanish side of the border. The water seeps underground before emerging at the top of the cliff face. The flow rate varies dramatically by season. The average annual flow is 3 cubic meters per second, but during the intense snowmelt of early summer, it can surge to 200 cubic meters per second. In winter, the waterfall can freeze completely, halting its flow. The water from the falls forms the headwaters of the stream Gave de Pau.