covered by a younger layer of rock. The Goat Rocks area is notable for its extensive glaciers, despite its modest elevation and southerly location relative to the rest of the Washington Cascades. Four major glaciers mantle the north and northeast slopes of the peaks: Conrad Glacier, McCall Glacier, Meade Glacier, and Packwood Glacier, along with numerous smaller permanent snowfields. Major peaks in the Goat Rocks vicinity The elevation of the Goat Rocks volcano and its immediate vicinity varies from to at its highest point, Gilbert Peak. Because of extensive glaciation and erosion, the peaks surrounding Goat Rocks are at most moderate in height. Eruptive history Goat Rocks is a stratovolcano with a somewhat complicated eruptive history. It first became active approximately 3.2 million years ago during the Pliocene epoch, undergoing explosive eruptions that ejected silicic lava with highly felsic rocks like rhyolite. One of these events produced of tuff that remains, exposed, on the east flank of the existing mountain. This rhyolitic episode also produced the Devil's Horn caldera. The amount of rhyolite tuff exceeds 20 km3 (4 mi3). Three million years ago Goat Rocks shifted to mafic volcanism, erupting olivine and basalt. As eruptions continued into the Pleistocene epoch, the lava flows became increasingly andesitic, containing mostly pyroxene with phenocrysts as well as hornblende minerals. These andesitic flows formed the volcano's major edifice between roughly 2.5 and 0.5 million years ago, which may have resembled contemporary Mount Rainier. At this point in time, Goat Rocks's eruptions had very high volumes and extended far from the volcano, possibly because multiple satellite vents contributed to eruptions. Approximately 1.64 million years ago, Goat Rocks generated an andesitic lava flow extending down the Naches and Tieton Rivers, which has been recognized as the longest andesite flow on Earth having a total volume of 6.6 km3 (1.6 mi3). About 250,000 years after this andesite flow a second flow erupted from Bear Creek Mountain, the second flow took a similar path as the older one and had a total volume of 2.5 km3 (0.6 mi3). Many of the flows immediately surrounding the volcano have since been cut by intrusive dikes, which form a radial arrangement around the volcano's core. As erosion occurred on a large scale, the volcano remained active, producing more hornblende andesite lava flows. Eruptive activity continued at Old Snowy Mountain into the middle to late Pleistocene, yielding hornblende andesite lava flows that