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 near each other. Geology Grand Teton National Park has some of the most ancient rocks found in any American national park. The oldest rocks dated so far are 2,680 ± 12 million years old, though even older rocks are believed to exist in the park. Formed during the Archean Eon (4 to 2.5 billion years ago), these metamorphic rocks include gneiss, schist and amphibolites. Metamorphic rocks are the most common types found in the northern and southern sections of the Teton Range. 2,545 million years ago, the metamorphic rocks were intruded by igneous granitic rocks, which are now visible in the central Tetons including Grand Teton and the nearby peaks. The light-colored granites of the central Teton Range contrast with the darker metamorphic gneiss found on the flanks of Mount Moran to the north. Magma intrusions of diabase rocks 765 million years ago left dikes that can be seen on the east face of Mount Moran and Middle Teton. Granite and pegmatite intrusions