Bitterroot Valley Glacial Erratics
Two glacial erratics in the Bitterroot Valley, the Lone Rock School erratic and the Rome Lane erratic, were deposited during the last high stand of Lake Missoula about 13,000 years ago. Both these glacial erratics are easy to visit. At the extreme Southern end of the Bitterroot Valley is beautiful Lake Como named after its Italian alpine counter part by Father Ravalli a Jesuit Black Robe tasked with bringing literacy and Jesus to the native Salish people in 1845 via St Mary’s Mission in nearby Stevensville. Lake Como is a beautiful place for lunch and a hike/bike on the trail around lake including a beautiful waterfall a the head of the lake. Several mountain glaciers coalesced here and neighboring drainage to make the largest mass of ice calving into the lake south of the Flathead lobe of the Cordilleran ice sheet at Polson. This mass exited the mountains, floated into and calved into Glacial Lake Missoula. This was the primary iceberg generator for the Bitterroot Valley. As they floated out into the lake and melted they dropped large rocks called erratic onto the lake floor, which is now the surface of the valley. Lone Rock School Erratic The easiest one to find is the Lone Rock School erratic. From Stevensville, proceed north on the Eastside Highway, county road 269, to the junction with county road 268, turn right. Follow county road 268 until you reach the Lone Rock School on your left; the erratic is the large boulder in front of the south side of the school, and behind the fence (see map below). The Lone Rock School erratic is 69” tall, 58” wide, 85” long, and weighs in at about 8.5 metric tons or about 18,700 lbs. This large erratic is a type of granite called quartz monzonite. The minerals that make up this rock type are, in order of abundance, plagioclase (calcium and/or sodium rich) feldspar, orthoclase (potassium rich) feldspar, biotite (dark mica), and quartz. If you look closely you will see that the quartz typically stands out in relief with respect to the other minerals and that its surface has been polished to a smooth finish. This is the result of dense glacial ice grinding over the surface of the rock. Rome Lane Erratic The Rome Lane erratic measures 47” tall, 117” long, 96” wide, and weighs in at about 13 metric tons or about 28,600 lbs. The Rome Lane erratic is almost identical to the Lone Rock School erratic; it to is quartz monzonite granite with approximately the same minerals and mineral proportions. The observation that both erratics are of similar rock type suggests that they came from a similar source region. There are sources of quartz monzonite granite in both the Sapphire and Bitterroot Mountains, which is the source of these erratics? Since we know that the erratics were carried to the shores of glacial Lake Missoula by glaciers, we can rule out the Sapphires as a possible source because we know that no glaciers in the Sapphire Mountains ever reached the shores of Lake Missoula. So, the erratics had to come from the Bitterroot Mountains where the quartz monzonite granite lies anywhere between 5 and 20 miles from the ancient shoreline of Lake Missoula. That means glaciers carried the erratics for distances of up to 20 miles (32.2 km) before reaching the shores of glacial Lake Missoula. Which at an average velocity of 5 meters per day (normal for most valley glaciers with the exception of rare bursts in velocity up to 75 meters per day) would take about 18 years. Which Erratic is Oldest? The quartz grains on the surfaces of the Rome Lane erratic are polished to a smooth shine and stand out in relief above the other minerals, similar to the Lone Rock School erratic. However, the quartz grains exposed on the top surface of the Rome Lane erratic seem to exhibit higher relief than the quartz grains exposed on any other side of the Rome Lane erratic and/or the top surface of the Lone Rock School erratic. Why is this? Rainwater is slightly acidic and acidic fluids can break down some minerals, such as feldspar, and turn them into clay. Quartz, however, is very resistant to acidic fluids and as a result takes longer to break down or weather. It is this difference in weathering rates between feldspar and quartz that causes the quartz grains to stand higher than the feldspar grains. So, based on this relationship we can say that the greater the relief between quartz and feldspar on a rock surface, the longer that surface has been exposed to the elements i.e. rain and wind. With that in mind, which erratic’s top surface has been exposed longer? If you answered Lone Rock, you are correct. As it turns out the Lone Rock School erratic was dug up and moved from its original location, about ¾ of a mile to the south of where it sits today, to commemorate the Lone Rock Schools’ centennial in 1985, in fact upon its excavation portions of the erratic broke off and remain buried. So what is the top surface of the Lone Rock School erratic today may well not have been the top surface before 1985, and our mineral weathering hypothesis fits the facts.
Erratic in the Bitterroot
An 8 ton erratic left behind by Glacial Lake Missoula in the Bitterroot Valley on the property of a local rancher was relocated to serve as the focal point of an outdoor kiosk exhibit at the Ravalli County Museum at the former County Courthouse, 205 Bedford Street in Hamilton. Unlike their counterparts at other location along the National Geologic Trail, erratics in this part of the Ice Age Floods did not come from Canada nor did they travel as far, but the action of the floodwaters and iceberg rafts is equally evident despite more shallow waters. There are similar erratics found elsewhere in Bitterroot, on the campus of the University of Montana, and at the Bison Range. The outdoor display tells the same story as other locations on the Ice Age Floods National Geologic Trail but also includes information on two other National Park Service trails that pass through this area – the Nez Perce and the Lewis and Clark National Historic Trails. The museum has other indoor exhibits of historical interest and about Glacial Lake Missoula.
Little Money Creek Gulch Fill
Mounds of soil, sand, gravel, and other coarse materials covered with light vegetation can be seen in the side gulches all along the Flathead River where tributaries drained into what was Glacial Lake Missoula. They were deposited by currents eddying into the slower water in these gulches and also by the drop in velocity of the streams carrying deposits from higher elevations on the far side of the river along the path of the escaping floodwaters. The flow of floodwaters through this narrow valley was estimated by J.T. Pardee at between 8 and 10 cubic miles per hours – more than the combined flow of all modern rivers in the world. Similar gulch fill can be seen in many locations along this beautiful stretch of the river, which today generally flows smoothly and looks completely flat. There are numerous pull-outs along MT 200 between Perma and Paradise; the view pictured here is at mile marker 91.
Camas Prairie Ripples
Camas Prairie Ripples The Camas Prairie Ripples, located 12 miles north of Perma, Montana, appear as prominent ridges 15 to 50 feet high, 100 to 250 feet wide, and from 300 feet to a half-mile long – the largest ripples on earth. While the form, structure and arrangement of these features are similar to that of ordinary current ripple marks, they are termed giant flood ripples, due to their large size. Most ripples that are formed by rivers today are only inches high and are mostly made up of sand-sized particles. Many of the Camas Prairie ripples are composed of boulder-sized geologic debris, and since the size of ripples is related to the strength of a river’s currents, these ripples were created by currents so powerful they are difficult to comprehend. The best examples of giant flood ripples are found in Camas Prairie. The Camas Prairie Ripples were formed by strong currents associated with as many as 40 to 100 emptyings of Glacial Lake Missoula over 4,000 years beginning some 17,000 years ago. Glacial Lake Missoula was formed by a massive lobe of the Pleistocene Cordilleran ice sheet that blocked the mouth of the Clark Fork River at Lake Pend Oreille, Idaho, a result of successive advances of the Cordilleran Ice Sheet during the Ice Age, when mammoths, saber-toothed cats, and giant ground sloths still roamed the landscape. It was the largest of several lakes impounded by the Cordilleran Ice Sheet in the Northern Rocky Mountains during the Quaternary period. The lake that formed behind the ice dam expanded until it was 3,000 square miles, held 500 cubic miles of water, and was 2,000 feet deep – as big as Lakes Erie and Ontario combined. It occupied the Mission, Jocko and Little Bitterroot valleys, drained by the Flathead River; and the Missoula, Ninemile and Bitterroot valleys, drained by the Clark Fork River. When the ice dam eventually collapsed Glacial Lake Missoula emptied catastrophically to the west on across the Columbia Plateau and down the Columbia River Basin, its waters moving at maximum speeds of 80 miles per hour to the Pacific Ocean. The flood waters ran with the force equal to 60 Amazon Rivers and moved car-sized boulders up to 500 miles, embedded in icebergs from the failed ice dam. It occupied the Mission, Jocko and Little Bitterroot valleys, drained by the Flathead River; and the Missoula, Ninemile and Bitterroot valleys, drained by the Clark Fork River. It is estimated that the catastrophic flood waters of Glacial Lake Missoula, 1,000 feet deep at Eddy Narrows, drained at a peak discharge rate of 10 cubic miles per hour. Approximately 380 cubic miles of water passed through those narrows, during withdrawal. Evidence of this catastrophic withdrawal can be found in scourings, high eddy deposits of flood debris, flood bars of boulders and course gravel, and successions of giant arcuate ripples or ridges of gravel resting on bedrock surfaces. The giant flood ripples at this site are unusual due to their being on the down-current side of notches in a ridge separating two basins that were both subsidiary to the main course of Lake Missoula in the Clark Fork Valley. Flathead Land Trust’s largest conservation easement protects 3,867 acres of the Camas Prairie near Hot Springs. The rolling grasslands of the Camaroot Ranch were first homesteaded in 1910, the year the Flathead Indian Reservation was first open to land acquisition. The Cross family’s ownership began in 1920 when Sid Cross’s grandparents, John and Anna Lauraman, first acquired 160 acres. They and other relatives continued to acquire surrounding land over the next several decades. At one time the ranch totaled almost 6,000 acres. Parts of three homesteads still remain on the property including a 2-story house and old barn that was built in the 1920s where Anna Lauraman grew up. The ranch was used for grazing cows and horses, and raising some crops such as alfalfa and wheat. The Cross family sold the property to the Confederated Salish and Kootenai Tribe in 2015. The conservation easement on this unique property preserves open space, agricultural land, and the giant ripples as silent monuments of Montana’s prehistoric and chaotic past. The locale includes a mixture of private, public and landtrust lands throughout the Camas Prairie area.
Bison Range
Bison Range The Bison Range was established by President Theodore Roosevelt in 1908 to conserve the American Bison. Since that time it has been managed as a wildlife refuge and native grassland. Today the management is done by the Confederated Salish and Kootenai Tribes. The range is a small, low-rolling mountain connected to the Mission Mountain Range by a gradually descending spur. Range elevation varies from 2,585 feet (788 m) at headquarters to 4,885 feet (1,489 m) at High Point on Red Sleep Mountain, the highest point on the Range. Much of the Bison Range was once under prehistoric Glacial Lake Missoula. The upper part of the Range was above water. Red Sleep Mountain scenic drive leads to this high point, which has spectacular views across what was once the lake to the Mission Mountains on the other side. Other flood features are evident on Buffalo Prairie scenic drive. Old beach lines (strandlines) can be seen on north-facing slopes and some large erratics are located near the old corrals. There is a visitor center near the entrance which has a display and videos of Glacial Lake Missoula as well as information on the tribes of the Flathead Reservation and the abundant wildlife, including birds, bears and antelope. There is also a gift shop. Camas Prairie ripples and several other important features of Glacial Lake Missoula are in close proximity to this site, much of them are located on tribal lands. The entrance is off US 93 and MT 212 N about an hour north of Missoula. Bison Range58355 Bison Range Rd, Moiese, MT (406) 644-2661 bisonrange.org FEES – there is a fee for entrance, including the day use area, except for CSKT tribal members OPEN HOURSWinter Hours (Nov-April)Gate: 8am–6pmVisitors Center: 8am–5pm Red Sleep Drive: closed Buffalo Prairie Drive: 8am-6pm Summer Hours (May-Oct)Gate: 7am–8pmVisitors Center: 8am–7pm Red Sleep Drive: 8am–7pm Buffalo Prairie Drive:8am–8pm Restrictions: Vehicles over 30 feet long and those owing trailers as well as motorcycles, ATVs, and bicycles are not allowed on either drive. Visitors must remain inside vehicles at all times except for designated areas
The Paradise Center
The Paradise Center Ice Age Floods National Geologic Trail Paradise Center, formerly the Paradise Elementary School, is a community, visitors, and arts center in the old railroad community of the same name. Just below the confluence of the muddy Clark Fork and beautiful blue Flathead Rivers, 70 miles northwest of Missoula, the area was repeatedly inundated by Glacial Lake Missoula, leaving many visible features in the area such as gulch fills, kolks, and lake bottom sediment bluffs. It is on the route between the Camas Prairie Ripples and Eddy Narrows. Inside the school is a unique interactive 3-D topographical or relief map of the entire area covered by Glacial Lake Missoula and an extensive display of information about the Lake as well as other topics of interest to the area. Outside on the grounds is a playground and an outdoor walking loop with a dozen or so displays of interest such as the former railroad roundhouse. A model railroad set-up is also found inside the center. This area can easily be reached directly from the St. Regis exit from I-90 by following the Clark Fork River where flood waters turned sharply to the north, carving out the narrow valley along scenic route 135 to the junction with MT-200. Scour marks and displaced boulders are visible from the road, and it is especially lovely when the larch trees turn bright yellow in the fall. This route also takes you past the historic Quinn’s Hot Springs Resort. ANNOUNCEMENT: The Paradise Center hours are seasonal, generally Wednesday thru Saturday, 11am-3pm in the summer. Check the website at paradisecentermt.org or call 406-826-0500 Quick Facts Location:2 School House Hill Road Paradise, MT 59856 MANAGED BY:The Paradise Center
Montana Natural History Center
Montana Natural History Center Ice Age Floods National Geologic Trail The mission of the Montana Natural History Center is to promote and cultivate the appreciation, understanding, and stewardship of nature through education. Founded in 1991, MNHC was the brainchild of a group of educators who were involved in various efforts to educate both kids and adults about the natural history of western Montana, and who decided to unite those efforts into one environmental education organization. MNHC provides nature education programming for people of all ages through summer camps, kids’ activities, Visiting Naturalist in the Schools, Master Naturalist certification courses and Field Days, evening programs, Field Notes on Montana Public Radio, museum tours, and more. We have a variety of exhibits that focus on the flora, fauna, geology, and ecology of our beautiful state. Please stop by and visit! MNHC often partners with the Ice Age Floods Institute to share fields trips and lectures about the Ice Age Floods. MNHC has exhibits that help visitors explore the Glacial Lake Missoula and Ice Age Floods. Learn more at:Explore Glacial Lake Missoula | Montana Natural History Center (montananaturalist.org) The Glacial Lake Missoula Chapeter of the Ice Age Floods Institue also produced a short movie about Glacial Lake Missoula. You can find a link here. Quick Facts Location:120 Hickory Street, Suite A, Missoula, Montana
Eddy Narrows
Eddy Narrows Ice Age Floods National Geologic Trail Eddy Narrows is a 10-mile long canyon between Plains and Thompson Fall along the Clark Fork River. Here all of the waters from the northern and eastern arms of Glacial Lake Missoula converged and picked up speed as they were forced through this restricted area. The steep valley walls are bare of talus and soils up to the level estimated to be the highest level of the lake (1000 ft), and there are polished grooves in the bedrock on a bench 340-400 feet above the Clark Fork River that run parallel to it. Since there is no evidence of glaciation in this area, the only explanation is the rapid draining of Glacial Lake Missoula. Using the dimensions of this flume-shaped area of the canyon, which controlled the rate of flow of water surging through it, in 1942 J.T. Pardee was able to calculate maximum speeds approaching 80 mph, emptying Glacial Lake Missoula in as little as three days. There are pullouts along MT-200 at either end of the narrowest part of this section marked for observing big horn sheep with Glacial Lake Missoula signage at the one between mileposts 59 and 60 at: 47.537940, -115.071654 Quick Facts Location:Between Plains and Thompson Falls, MT
Glacial Lake Missoula Strandlines
Glacial Lake Missoula Strandlines Ice Age Floods National Geologic Trail Imagine you are standing on the edge of glacial Lake Missoula 15,000 years ago. You can hear lapping waves cutting benches known as “strand-lines” into the shoreline. Today, you can see these huge strand-lines on hills surrounding Missoula, Montana, marking changes in lake level over time. On Mount Sentinel, marked with an “M”, and Mount Jumbo, marked with an “L”, the strand-lines are seen as horizontal lines in the vegetation or highlighted by snow in the winter. Public hiking trails switchback through the strand-lines on Mount Sentinel and Mount Jumbo. Ancient shorelines or strand-lines of Glacial Lake Missoula are visible as perfectly parallel horizontal benches on hillside slopes around Missoula. They are most visible with light snow cover, or in low evening light on the mountains marked with an”M” and an “L” on either side of Hellgate Canyon looking east from the downtown. These shoreline benches cut by wave action in the lake recorded various lake levels as the ice dam blocking the Clark Fork River far upstream on the Idaho border repeatedly failed and refilled 40 times or more. It may be that as the ice-age waned each successive ice dam that reformed was smaller and failed under less pressure from a lower lake level than the one before, leaving behind its bench as a record of the successively lower ancient lake shorelines. It’s also possible they record winter still-stands in rising lake levels over time. Quick Facts Location:The Kim Williams Trail at Van Buren and 5th Street leads from the U Montana campus along the river between the mountains. To reachhigh water markers on the mountains see the Interactive Map or go to GlacialLakeMissoula.org
Glacial Lake Missoula National Natural Landmark
Glacial Lake Missoula National Natural Landmark Ice Age Floods National Geologic Trail Glacial Lake Missoula was the largest of several lakes impounded by the Cordilleran Ice Sheet in the Northern Rocky Mountains during the Quaternary period. The lake was approximately 2,900 square miles in size and contained more than 500 cubic miles of water. It occupied the Mission, Jocko and Little Bitterroot valleys, drained by the Flathead River; and the Missoula, Ninemile and Bitterroot valleys, drained by the Clark Fork River. The lake was formed by an ice dam across the mouth of the Clark Fork River at Lake Pend Oreille, Idaho, a result of successive advances of a lobe of the Cordilleran Ice Sheet. The site is located 12 miles north of Perma, Montana.At least three and possibly more than 100 separate collapses of the ice dam, possibly coincident with periods of ice retreat, caused the lake to drain, producing catastrophic floods across the Columbia Plateau and down the Columbia River Basin. It is estimated that the waters of Glacial Lake Missoula, 1,000 feet deep at Eddy Narrows, were withdrawn at a peak discharge rate of 10 cubic miles per hour. Approximately 550 cubic miles of water passed through those narrows during withdrawal. Evidence of this catastrophic withdrawal can be found in scourings, high eddy deposits of flood debris, flood bars of boulders and course gravel, and successions of giant arcuate ripples or ridges of gravel resting on bedrock surfaces. Ripples appear as ridges 15 to 50 feet high, 100 to 250 feet wide, and from 300 feet to a half-mile long. While the form, structure and arrangement of these features are similar to that of ordinary current ripple marks, they are termed giant flood ripples, due to their large size. The giant flood ripples at this site are unusual due to their being on the down-current side of notches in a ridge separating two basins that were both subsidiary to the main course of Lake Missoula in the Clark Fork Valley. The best examples of giant flood ripples are found in Camas Prairie. Quick Facts Designation:National Natural Landmark OPEN TO PUBLIC:Private Land, closed to the public, but features throughout the area are visible from many vantage points.