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Marc Hendrix (Photo courtesy of Cary Shimek)

Q: Marc, your current work includes the study of sediment from the Pleistocene and Holocene epochs, and the impact of climate change during those times. I believe we often refer to the Pleistocene as the Ice Age. What was going on in what we now call Montana during the end of the Ice Age in regards to glaciation and climate change?

A: The end of the last episode of significant glaciation in Montana occurred around 14,000 years ago, in what most folks call an Ice Age. Beginning around then and proceeding for the next thousand years or so, an extensive set of mountain glaciers began to retreat. Over some of Montana's major mountain ranges and plateaus, glacial ice that had built up during the glacial maximum formed an ice cap that flowed downslope off the range crest or plateau in all directions, feeding the valley glaciers downslope. Ice caps of significant size formed over the Yellowstone and Beartooth Plateaus and the area along the Continental Divide in the northern part of Montana.

In northernmost Montana, an even more extensive set of ice sheets that formerly had crept southward out of Canada during the peak of the last glaciation began to retreat northward, shrinking as they melted. These ice sheets were continental in size. The biggest was the Laurentide Ice Sheet, located east of the Continental Divide and centered over northern Canada. In Montana, the Laurentide Ice Sheet had advanced southward far enough to cause the Missouri River to shift its course to its present position. West of the Continental Divide, the Cordilleran Ice Sheet – which was centered over the Canadian Rocky Mountains – advanced as far south as Polson, on the southern shore of Flathead Lake. The Cordilleran Ice Sheet also fed the Purcell Trench Lobe, the glacier that ultimately blocked the Clark Fork River Valley and impounded glacial Lake Missoula. As these glaciers began to melt, the landscape across western and northern Montana changed fast. Not only was a lot of ground re-exposed by the melting and retreating ice, but the dynamics of the melting process itself gave rise to occasional large floods of water that carried significant volumes of sediment. Much of this sediment was deposited in Montana’s western valleys. These deposits now form some of the state's most important aquifers.

Q: How do sediments provide evidence of climate and climate change?

A: Sediments reflect much about the environment in which they were deposited. In many cases, sediments can be used as a sort of historical archive for environmental change. In some situations, the fidelity of this historical record can be high (like a high fidelity recording) and it is these high fidelity records that are most useful for understanding past climate change.

There are many ways the sediment record reflects past climate. At the most basic level, by documenting the types of sediment (mud, sand, gravel) and their physical arrangement (well-layered, massive, pod-shaped, etc.), geologists can make inferences about the types of environments that existed in the past. Ideally, the sediment record in these situations contains datable material – that is, something useful for providing numeric age information like organic carbon or a layer of volcanic ash. At a more refined level, some individual sediment accumulations can yield high fidelity climate information useful for studying shorter duration environmental changes such as variations in wildfire regime. These high fidelity sediment records might permit the documentation of environmental changes that take place over timescales ranging from decades to millennia.

This latter approach is sometime called the ‘time-series approach’ because the data used to interpret past climate is cast in the form of variations in something through time. The ‘something’ might be a particular diatom (single-celled algae) or some other fossil, including charcoal from prehistoric wildfires; some geochemical parameter (carbon to nitrogen ratio); or a physical attribute, like the median grain size of sediment. Precisely how these so-called ‘proxy data’ reflect quantitative estimations of past climate is the subject of a lot of debate among scientists, although time-series data represent an efficient means of obtaining high resolution information about past environmental change.

Q: Your work with sediments has perhaps tarnished one of Montana’s most cherished geologic legends: that Glacial Lake Missoula - supposedly larger than lakes Erie and Ontario combined - repeatedly and catastrophically broke through its ice dams and gouged a course to the Pacific Ocean, creating formations such as the scablands of eastern Washington and the Columbia River Gorge. What’s your side of the story?

A: Well, certainly much of glacial Lake Missoula’s fame is well-deserved. After all, the lake had a surface area of around 500 square miles, was nearly 1000 feet deep in the Missoula Valley and deeper further to the west, and was responsible for shaping many of the famous landscapes of western Montana. The connection between glacial Lake Missoula and the erosional landforms of eastern and central Washington State that first were made by J.T. Pardee and J. Harlan Bretz was something of an epiphany, and for a long while, this idea seemed to be regarded by many as the only explanation for the formation of the Channeled Scabland and other erosional features in Washington State. Nobody seemed bothered by the fact that the entire Cordilleran Ice Sheet that once stretched from Glacier Park to the Olympic Peninsula in coastal Washington State is now gone. But the idea that glacial Lake Missoula provided the only source of flood waters that could have carved the Channeled Scabland seems geologically implausible to a number of geologists, including me. Certainly that connection is there, but other sources of water almost certainly also played a role in the formation of the erosional landforms of Washington State. Much of that water probably came from deglaciation of the Cordilleran Ice Sheet between the Continental Divide and crest of the Cascade Mountains in Washington.

For the past decade or so, my students and I have been conducting research on the sedimentary record of glacial Lake Missoula, mainly oriented around documenting the distribution and nature of glacial lake deposits. Surprisingly, despite the fact that glacial Lake Missoula is world-famous, very little is known about its sedimentary record. Until the excellent work of Larry Smith from Montana Tech came out a few years ago, no one had even been able to unequivocally demonstrate that the lake filled and drained more than once. My own interpretation of glacial Lake Missoula is that it did fill and drain at least twice and at least one of these draining events was catastrophic. Not only did this draining produce the massive gravel flood bars documented by Larry Smith in the lower Clark Fork River Valley, but rapid deposition of coarse sediment where the draining lake waters funneled from tight canyons downstream into more open valley regions helped produce some of the best aquifers in the state, including the Missoula aquifer. So, I would like to be clear in stating that I do subscribe to the hypothesis that glacial Lake Missoula drained catastrophically at least once and that it existed and drained at least twice. Likely, it filled and drained catastrophically more times than that. However, at present, the sedimentary record within the lake basin itself does not indicate unequivocally that the lake filled and drained dozens or hundreds of times as others have claimed. Perhaps more to the point, the interpretation that each of the dozens of floods deposits documented in the Walla Walla Valley and elsewhere in Washington State came from a separate draining of glacial Lake Missoula is not yet demonstrated.

Q: You’ve also studied some geologic characteristics of Flathead Lake. There is a major fault under its eastern shore that is largely responsible for creating the lake. What is it about the fault that makes this so? Are there other lakes in Montana with a similar origin?

A: The fault under the eastern shore of Flathead Lake is the northern extension of the Mission Fault, which runs up the western flank of the entire Mission Range from the St. Ignatius area roughly to Bigfork. The Mission Fault is extensional, meaning that it forms by pulling apart the Earth’s crust, in this case in an east-west direction. The fault dips to the west into the subsurface, and the western side of the fault is downdropped relative to the eastern side. The amount of offset on the Mission Fault seems to decrease to the north, and the fault itself changes from a single strand fault in the southern Mission Valley/Mission Range to a multi-strand fault under the eastern part of Flathead Lake. There, not only is the lake being slowly downdropped by the fault, relative to the northern Mission Range immediately to the east of the lake, but within the lake, downdropping along some of the individual fault strands has produced the deep trough that defines the lake’s bottom topography (bathymetry) along its deep eastern side. Parts of this trough are being downdropped by two small fault segments that are situated roughly parallel to each other and oriented such that the block of lake floor between them drops downward like a settling keystone block.

Although other downdropped valley systems occur across western Montana, most do not impound major lakes. Flathead Lake is somewhat unique in this case in that it is impounded by the Polson Moraine – a berm of sediment left behind by the Flathead Lobe of the Cordilleran Ice Sheet.

Q: We have heard that western Montana is ripe for a major earthquake. What area or areas are the most vulnerable and what magnitude of quake do you expect and why?

A: I think that the area around the shores of Flathead Lake is among the most vulnerable. Not only is this area situated very close to the northern Mission Fault, but the Swan Fault – another very large extensional fault – is located only a short distance to the east. Like the Mission Fault, the Swan Fault downdrops the Swan Valley relative to the Swan Range. In fact, slow movement along both the Mission and Swan Faults has in effect tilted the entire Mission Range to the east, so that the rock layers throughout the entire range dip eastward. Fault-trenching work along the Mission Fault conducted by the Bureau of Reclamation in the early 1990s indicated that two large earthquake-producing ruptures have occurred within the last 15,000 years or so. The most recent occurred roughly 7,700 years ago. Both of the prehistoric earthquakes documented from the fault trenching studies were estimated to have been about magnitude 7.0. Thus, the Mission Fault not only appears to have produced major earthquakes in the past, but the last one occurred thousands of years ago, suggesting that strain may have been building on the fault now for some time.

Not only could a major rupture occur on either the Mission or Swan Faults and produce a significant earthquake, but sudden downdropping of the floor of Flathead Lake could send a large wave of water, called a seiche, sloshing back and forth across the lake. In addition, a number of dams that currently impound moderate-sized reservoirs in the area could fail, sending a large flood downstream.

This said, pretty much all of western Montana is in a seismically hazardous area. A major rupture on the Mission or Swan Faults would cause significant damage in Missoula and Kalispell. Similar active faults near the other major population centers in western and central Montana also pose significant seismic risk.

This program is excellent for group meetings, conferences, board meetings and in schools. For teachers, the program is accompanied by three lesson plans. To schedule a presentation, please contact Mike Bader at (406) 721-4835 or mbader@montana.com You can see and learn more about the Native Fish Project, including downloadable special reports, at http://www.clarkfork.org/programs/native-fish-education.html.

The conference cost is $110 for early registration up until 8 a.m. on Thursday, September 24. After that time the cost is $130. Students can attend the conference for free, but must register and need to pay for their lodging, if needed. The whole pig roast banquet is $30. Kirk Waren will be in charge of the banquet entertainment and plans an epic photo odyssey through Montana’s waters and wilds. Kirk plans to develop some categories based on the photos submitted. Suggested topics include scenic hydrology, field work, laboratory work, humorous, and field trips or classes. Submit your high resolution photos to Kirk at KWaren@mtech.edu or contact him for more information.

An agenda will be posted soon at the conference website at http://awra.org/state/montana/events/conference.htm and the conference registration site will open on August 1, 2009.

This National Science Foundation program makes grants to colleges and universities to support scholarships for academically talented, financially needy students, enabling them to enter the workforce following completion of an undergraduate or graduate-level degree in science and engineering disciplines. At this time, a sizeable amount of money seems to be available. Students will need to work with their advisors and financial aid office in order to apply. For more information go to http://www.nsf.gov/pubs/2009/nsf09567/nsf09567.htm?govDel=USNSF_25.

DEQ Mini Grants

The Montana Department of Environmental Quality is offering mini-grants of exactly $1,500 to fund local education and outreach efforts that address water quality issues. Applications are due by July 1, 2009. Approximately $12,000 will be available for this round. For applications and more information, visit http://deq.mt.gov/wqinfo/nonpoint/NonpointSourceProgram.asp.

DEQ also has $15,000 available to assist local volunteer monitoring groups with water analysis laboratory services. These groups include, but are not limited to, watershed groups, 319 grantees, conservation districts, water quality districts, 501(c)(3)s, and schools. Applications will be awarded on a first come-first serve basis, and each group will have a maximum of $2,000 which must be spent by June 30, 2010. For more information, download http://deq.mt.gov/wqinfo/nonpoint/2010_VM_Call_AppFinal.pdf. Contact Kristy Zhinin, kzhinin@mt.gov, (406) 444-7425 prior to submittal to assure your application is complete.

Despite a wave of new technologies, no single solution can address every possible pollutant or contaminant. This article advises a “portfolio approach” to clean water technologies. To read the article, visit http://waterefficiency.net/the-latest/luxresearch-pollutants-treatming.aspx.

New Approaches to Crop Irrigation

Traditional ways of irrigating crops are changing under the pressure of water scarcity as new technologies emerge. This article analyzes the technologies and offers new approaches. To read the article, visit http://waterefficiency.net/january-february-2009/swat-away-wasted.aspx.

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Take special note of upcoming national and local water meetings on the Events Calendar at MONTANA WATER.