The glaciers of the Sierra Nevada

The mountain range of Sierra Nevada is c. 90 km long and located in the southeast of the Iberian Peninsula. Its highest peak, the Mulhacen (3479 m; 37o 03′ 12″ N, 3o 18′ 41″ W), is also the highest in the Iberian Peninsula. Sierra Nevada is part of the Betic Range, which crosses the southeastern part of the peninsula from southwest to northeast. It is composed of metamorphic and crystalline rocks that folded and fractured during the Alpine orogeny. The average annual temperature is 4.4°C, and the recorded precipitation at an altitude of 2500 m is 710 mm. The Pleistocene glaciers of the Sierra Nevada, the southernmost in Europe, were enclosed in the headwaters of ancient valleys, and their maximum lengths ranged between 6 and 9 km. Some moraines from the previous glacial cycle (130 ka) can be found here, but most of them belong to the Last Glacial Cycle, whose maximum advance occurred at c. 30 ka. An advance of almost similar proportions took place at approximately 20–19 ka, followed by a massive deglaciation until a new advance occurred in the Oldest Dryas. After the probable almost total disappearance of the glaciers, small cirque glaciers formed during the Younger Dryas. The glaciers melted away at the beginning of the Holocene, but rock glaciers formed simultaneously in numerous cirques. Later, during the Late Holocene, small glaciers formed only under the northern walls of the highest peaks (Mulhacen and Veleta), but disappeared at the end of the Little Ice Age, favoring the development of incipient rock glaciers.