destinations and is climbed year-round. Winter climbing requires advanced mountaineering ability. In spring, undercutting of deeply drifted snow by streams creates a hazard that has proven fatal on several occasions. Climbers can fall through the undermined snow or more into the icy stream underneath. Although it is a round-trip hike, with almost of elevation gain, Timpangos's summit is one of the most frequently visited in the Rocky Mountains. There are two main trails to the top: the first starts at Aspen Grove with a trailhead elevation of , and the second starts at the Timpooneke campground in American Fork Canyon at . The two trails are nearly the same length. Hikers on the trails climb through montane forest, subalpine and alpine zones. The hike is marked by waterfalls, conifers, rocky slopes and ridges, mountain goats, and a small lake, Emerald Lake, at . A short diversion will lead hikers past a World War II bomber crash site. Other climbing routes exist on the mountain, but they are more technically demanding and require special skills and mountaineering gear. Prior to 1970, an annual Provo event called the "Timp Hike" sent thousands of people up the mountain's slopes. From 1911 to 1970 this one-day event (which took place generally on the third or fourth weekend in July) attracted thousands of people to the mountain. It also created the need for infrastructure, such as the stone shelter built in 1959 near Emerald Lake and a smaller metal shack on the summit (this was used as an observation deck complete with brass rods etched with notches aligned with various landmarks). The hike caused environmental damage to the mountain, and was finally canceled to help preserve the delicate mountain ecosystem. Despite the presence of the existing structures, the mountain was designated a wilderness area by the U.S. Congress in 1984. Geology The rock which forms the visible surface of Mount Timpanogos is primarily limestone composed of compacted sediment laid down onto an ancient seafloor over millions of years during the late Carboniferous Period (roughly 300 million years ago). Older rock exists beneath the limestone on the surface. The limestone was subsequently lifted high above sea level and the mountain itself became prominent as the Western valley sunk due to basin and range faulting. The most contemporary features of the mountain were formed through recent glacial and water erosion. Hazards Since 1982 the Timpanogos Emergency Response