Along the ICE AGE FLOODS
NATIONAL GEOLOGIC TRAIL

Glacial Lobe Dam at Green Monarch Ridge View Point Ice Age Floods National Geologic Trail  As the Purcell Trench ice lobe of the Cordilleran Ice Sheet advanced south from Canada, it was stopped by the Green Monarch Ridge, building an ice dam 4,000 feet (1219 m) tall and nearly 40 miles (64 km) wide that blocked the Clark Fork river, thus filling glacial Lake Missoula. View the Green Monarch Ridge and the Purcell Trench from a large pullout on Idaho State Route 200, about one mile (1.6 km) west of Hope, Idaho and 15 miles (24 km) east of Sandpoint, Idaho. Quick Facts Location: Idaho State Route 200, about one mile west of Hope, Idaho and 15 miles  east of Sandpoint, Idaho.

Farragut State Park Ice Age Floods National Geologic Trail Farragut State Park is located at the “breakout” of Glacial Lake Missoula floods, where the ice dam in the Clark Fork valley and the 20-mile-long tongue of ice occupying the Lake Pend Oreille basin failed. From there, a torrent of water and ice burst from the south end of the lake. Farragut State Park is located at the “breakout” of Glacial Lake Missoula floods. Failure of the ice dam in the Clark Fork valley fractured and broke apart the 20-mile-long tongue of ice occupying the Lake Pend Oreille basin, and a torrent of water and ice burst from the south end of the lake. That churning slurry of flood waters, ice, boulders and other debris erupted from the south end of Lake Pend Oreille, flowing 2000 ft deep across Farragut State Park. Nearly all of the water escaping from Glacial Lake Missoula passed through this area. Discharge estimates range from 14 to 21 million cubic meters per second! Vic Baker’s definition of a megaflood is one which has a discharge of at least 1mil cubic m/s, so we are possibly looking at ground zero for the worst Pleistocene flood in the world. Farragut State Park includes many geologic features left by glaciation and megafoods.Hoodoo channel, an abandoned outlet of Lake Pend Oreille provided a pathway for late-glacial meltwater and for the last outbursts from Glacial Lake Missoula. The channel is marked with a number of closed depressions, probably the result of melting icebergs. One of the largest of these features have been proposed, including kettles, potholes, and sub-glacial meltwater. Some of that debris was deposited to form the Rathdrum Prairie Outburst Plain, an extensive, heterogeneous mix of flood deposits. Farragut State Park offers unique scenery, history and an abundance of recreational opportunities. Quick Facts Location:13550 E. Hwy 54 Athol, ID 83801 

Green Monarch Ridge Ice Age Floods National Geologic Trail THIS IS WHERE IT ALL BEGAN! The Green Monarch Ridge viewpoint, just south of the Hope Fault, is positioned along the edge of the Purcell Trench Ice Lobe. Here it was responsible for damming the mouth of the Clark Fork drainage basin. This damming effect resulted in the formation of Glacial Lake Missoula, the source of the waters for much of  the PNW Pleistocene Ice Age Floods. The Purcell Trench Ice Lobe originated in Canada and flowed south into Idaho, guided by the structural control of the Purcell Trench. Following the path of least resistance into the basin now occupied by Lake Pend Oreille, it was impeded by the Green Monarch Ridge, located approximately 10 miles south of this viewpoint. Grinding and scraping, the Purcell Trench Ice Lobe backed up behind the Green Monarch Ridge, eventually building an ice plug up to 4,000 feet thick, and scouring out the deepest parts of Lake Pend Oreille. The Purcell Trench Ice Lobe divided into four sub-lobes: one went approximately west (US Highway 2), two went south (US Highway 95 and Lake Pend Oreille) and one went east (SR 200). All four sub-lobes contributed to blocking the Clark Fork drainageQuick Facts MANAGED BY:US Forest Service – Idaho Panhandle National Forest