are only slightly smaller than the High Ajata flow and form superposed lava flows lower on the edifice. These lava flows are gray-black aa lava flows, commonly up to thick; the longest of these flows reaches a length of . Older are the large dacitic lava flows known as the "Border Dacites" on the southeastern side of Parinacota, which are over horizontal distance. A similar but smaller lava flow lies west of the Border Dacites, entirely within Chile. These three lava flows have a total volume of about . Overall, Parinacota rises from a surface of ; the resulting edifice has a volume of . On the northern side Parinacota partly overlaps with Pomerape. Parinacota, Pomerape, and volcanoes farther south like Quisiquisini, Guallatiri and Poquentica form the eastern margin of the Lauca basin. This is a relatively gentle plain drained by the Rio Lauca. A chain of dormant or extinct volcanoes farther west like Taapaca forms the western margin of the basin and separates the Altiplano from the steep dropoff to the Atacama west of the Lauca basin. Glaciers The old cone was subject to glaciation, and traces of glacial erosion are preserved on its lava flows. A system of moraines can be seen at an elevation of on the southeastern foot of the volcano, where they partly cross the shores of Lake Chungará. Six such high moraines have been identified there, they were formed during the regional last glacial maximum (which did not coincide with the global last glacial maximum) although a pre-last glacial maximum origin has been proposed. Other, unspecified glacial deposits have also been observed in this area. Presently, a or large ice cap covers the upper parts of the volcano and drops down to an elevation of about . There is also a large glacier on its southern flank. Some reports disagree with calling any part of Parinacota's ice cap a "glacier", however. Between 1987 and 2016, ice area at Parinacota and Pomerape declined by 1.94% every year. A retreat of was noted between 2002 and 2003, and most of the ice lies on the western slope of the mountain. Sector collapse Parinacota shows evidence of a major sector collapse (a giant landslide), whose deposit was originally interpreted to be a lava flow. The collapse removed a volume of about from the cone, plunged over vertical distance and flowed west, covering a surface area of or