The major peaks of the Teton Range were carved into their current shapes by long vanished glaciers. Commencing 250,000-150,000 years ago, the Tetons went through several periods of glaciation with some areas of Jackson Hole covered by glaciers thick. This heavy glaciation is unrelated to the uplift of the range itself and is instead part of a period of global cooling known as the Quaternary glaciation. Beginning with the Buffalo Glaciation and followed by the Bull Lake and then the Pinedale glaciation, which ended roughly 15,000 years ago, the landscape was greatly impacted by glacial activity. During the Pinedale glaciation, the landscape visible today was created as glaciers from the Yellowstone Plateau flowed south and formed Jackson Lake, while smaller glaciers descending from the Teton Range pushed rock moraines out from the canyons and left behind lakes near the base of the mountains. The peaks themselves were carved into horns and arêtes and the canyons were transformed from water-eroded V-shapes to glacier-carved U-shaped valleys. Approximately a dozen glaciers currently exist in the park, but they are not ancient as they were all reestablished sometime between 1400 and 1850 AD during the Little Ice Age. Of these more recent glaciers, the largest is Teton Glacier, which sits below the northeast face of Grand Teton. Teton Glacier is long and wide, and nearly surrounded by the tallest summits in the range. Teton Glacier is also the best studied glacier in the range, and researchers concluded in 2005 that the glacier could disappear in 30 to 75 years. West of the Cathedral Group near Hurricane Pass, Schoolroom Glacier is tiny but has well defined terminal and lateral moraines, a small proglacial lake and other typical glacier features in close proximity to each other.