Mysteries of the Glacial Lake Missoula Essay

            Sometimes history and science have been so technical that people get scared of just thinking what it meant. There are many mysteries in the world that have not been uncovered yet. There are still many things that science can’t explain. There are many things that history cannot tell. And there are many things that we see which we don’t know how they came about. Take for example, the channeled scablands. Many geologists had come to these sites to study and find out about their existence. Their first explanation was it formed during the Ice Age. It is due to long process of erosion and weathering. Then someone came up with suggestion that Missoula lake flood did it.

But in the midst of fear the curiosity arises. There are some questions that have to be answered yet. How come that in Missoula there is a giant ripple marks beside the mountains? Then you will realize how little we know about our planet. How little you know about the Missoula lake floods?

The Glacial Lake Missoula is one of the largest glacial lakes that occurred in the Earth. It is located west of Montana. Researchers estimated its maximum depth of about 4,200 feet (600 m).  And it contains about 500 cubic miles of water. It took place about 13,000 to 15,000 years ago (Oard). This is where the geologists believed the Missoula Great Flood originated. This flood is believed to be the cause of the channeled scabland in the Washington state.

There are many mysteries about the Glacial Lake Missoula and the Lake Missoula Flood. Many geologists have spent much of their lifetimes studying and uncovering their mysteries. Many postulates about the scablands have been formed and disproved over the past years. And there are still more and more studies being done to find out how the scablands were formed.

 About one hundred years ago, geologist began studying unique geological features in northern Washington. They found out the plains were underlined by thick basalt flow. There is a very thin layer of soil covering it. They also noticed the severely braided surfaces of the deep channels. That large area where these land forms where observed was then called the Channeled Scablands.

In the early times of the studies, geologists have believed that the scablands were a product of slow gradual process which occurred during the Ice Age. They simply rejected ideas which are not unifomitarian to explain the existence of the scablands.

In the past years, researchers have argued about where the scablands came from. The controversy started when J Harlen Bretz(1882-1981),an American geologist, suggested that the scablands were formed by enormously big flood with unknown source which shaped the geological features of the scablands and other distinct geological features in Washington. It was opposed by many geologists in the geological society because they believed that scablands were formed under the principle of uniformitarianism in geology.

            Uniformitarianism refers to a principle in science which says that the same processes which shaped the universe occurred in the past as they are occurring now and the same laws of physics were applied to every knowledgeable universe. This states that processes which occurred in the past could happen over and over again in certain time frame of cycle. This principle was widely used in the explanation of geological phenomena in those years. The principle was the idea of James Hutton which was modified by a Scottish geologist, Charles Lyell, into a theory of uniformitarianism. It was also said that the thinking pattern of the geologists who studied the cause of the flood was uniformitarian.

            Moreover in the later years in his research, Bretz believed that the catastrophic drainage of Lake Missoula in Montana was the cause of the flood.

            Many uniformitarian geologists presented rebuttal papers to counter Bretz`s theory. He has suffered many oppositions and debates about his theory. It took him many years for his theory to be finally accepted in the geological society.

In 1925, another geologist, Joseph Pardee, an American who works for United States Geological Survey, backed up Bretz?s postulate about the flood. In his research of the canyons of the Flathead River and other land features, he identifies where the big flood came from which Bretz’s postulate talked about. It came from the ice dam failure which occurred in the Pleistocene period. He identifies the ice dam as the Missoula Glacial Lake. He estimated the water flow to be 9 cubic miles per hour to shape the land forms in the scablands (Bjomstad). This postulate explains how Bretz’s catastrophic flood came into existence.

            It explains that in the Ice Age period about 13,000 to 15,000 years ago there existed an ice sheet, one of the major ice sheets formed during the Quaternary period, located at the northern part of Washington. This massive ice sheet that covered almost the entire Canada is called the Cordilleran Ice Sheet. Some of the parts of the Cordilleran ice sheet melts and refreezes to cause it to move southward to the northern part of Washington. The Cordilleran Ice Sheet consists of three main lobes: the Puget Lobe, Okanogan Lobe and the Purcell Lobe. As Cordilleran Ice Sheet moves, a finger of the Purcell Lobe blocks the Clark Fork River near the Idaho-Montana Border creating a massive 1,500-foot ice dam which became the Glacial Lake Missoula. The glacial lake covered over 7,800 square kilometers of Montana, approximately 2,000 square kilometers of surface water and about 600 meters deep. It contains a volume of water amounting to 1,200,000 cubic kilometers (500 cubic miles) (Bjomstad).

As water rises in the lake, more pressure was applied to the ice walls. The stress created ruptures where water goes in and out, creating a water current causing friction which melted the ice wall. This rapid melting was due to increasingly high current. Friction made the ruptures bigger and gradually weakening the dam. When dam fails, tons of water spilled out, which were called the jökulhlaup to the Clark Fork Valley, eroding great parts of the topsoil uncovering the bedrocks under them. Spilling out at the rate of 65 miles per hour, the flood reaches a height of about 2,000 feet. It transformed every land formation on its path, forming scablands and other geological features in the Washington State. He estimated that the Missoula drained in about 48 hours (Oard).

Pardee’s conclusion was based on the giant ripple marks he had discovered during his study. These giant ripple creeks have an average height of 15-30 feet and with the length of 250 feet (Pardee). These marks were extra ordinary. He postulated that this ripple creeks could be formed only by a fast flowing large body of water. He then associated  this giant ripple marks of gravels in Camas Prairie with the ice dam failure of the Missoula Glacial Lake. He calculated that the drainage rate is about 9.46 cubic miles per hour (Pardee). With this, he proved Bretz’s thoery on the catastorphic flood.

The controversy still lasted for many years until some uniformitarian geologist went there to study the evidences. In the 1960, a group of uniformitarian geologists examined the scablands. Bretz’s postulate had been proven by the overwhelming and obvious evidences that they found in the area. After that, these geologists made a uniformitarian postulate of the Missoula Flood stating that there is more than one occurrences of the Missoula Flood. By the uniformitarian principle, they suggest that the process on how the floods occurred repeats in certain time frame.

 Another controversy arises: how many floods occurred to shape the scablands? Another debatable topic was formed to keep the geologist busy.

            This started when Bretz postulated in 1951 that there had been up to seven floods. More researchers suggest that there is one to few floods. Until 1980, Richard Waitt suggested that there are about 40 Lake Missoula floods (Waitt). His evidence was based on the series of about 40 rhytmites in the Burlingame Canyons. The Burlingame Canyon is the Walla Walla Valley of the southeastern part of Washington. Richard Waitt and other explained that each rhythmite they found corresponds to one Missoula Glacial Flood (Waitt).

In 1960s, Pardee added that by the same process the ice dam refreezes, creating the glacial lake again. And as the water rises, it ruptures the ice dam again creating the enormous flood. He calculated that the process repeats about 40 times in 2000 years.

In 1986, the flood count goes up to 90 when 89 rhytmites was discovered by geologists. These rhytmites were separated to what they call varves found in the Sampoil Valley in the northeast of Washington. A total of 3,000 varves which intertwined with the rhytmites were found and 90 floods were calculated to have occurred within the 3,000 year period. This postulate was disregarded easily because the time frame does not fit the melting equations over ice and snow in the post-Flood Ice Age (Oard).

            Later, more geologists had gone to the explanation that there is just a few or just one Missoula Great flood. One geologist rejected the idea that one rhytmite corresponds to one Missoula flood. Then he suggested that one Missoula flood makes up two to nine rhytmites. When calculated, the flood count goes down to about 20 Missoula floods. Smith’s postulate encountered a lot of confusion since at any area where rhytmites were found the rhytmites were almost identical (Oard).

             Just a few years ago, eight investigators from the University of Alberta in Edmonton, Alberta, Canada went to the area to reexamine the evidences. They had concluded that there is only one Missoula flood. But, they had suggested that there are other floods, other than the one coming from the Missoula Glacial Lake, that have occurred. This postulate is still controversial and is subjected to further studies.

            Another issue was how the ice dam failed? This question arises when a geologist countered the analysis of Pardee of the flood. Since the explanation was not sufficient, many geologists have suggested possibilities. The way on how the dam fails is different but the location of the ice wall where the failure occurred was not changed.

            There are many possibilities which geologists suggested but these four are most used in the debates. One possibility is when the ice became buoyant because of the overwhelming amount of water it stored. This happens when the water creeps under the ice wall and lifts the wall, causing it to fail. Second is the water pressure which chips out the ice walls due to friction, making it deformed. When it is deformed it loses stability causing it to fall apart. Third is the existence of ice tunnels within the wall which the water gradually enlarges. The tunnels will come to appoint that it is large for water to break through causing the ice dam to be empty. And the fourth one is the existence of ice bergs which collides with the ice wall rupturing it which eventually breaks the wall apart.

            There are other questions which geologists considered debatable about the Missoula lake flood. Like how did water burst out? Is it over? Or is it under? Or the question is, is it gradual or one time?

            Many answers had been raised to answer these questioned but only few were acceptable.  Evidences were required for exact answers to be made.

Many studies had been published on how those magnificent land features came about. They tried to explain everything they discovered within those channeled scablands. But not all of them are accepted.

The Cordilleran Ice Sheet, one of the largest ice sheets formed in the Ice Age, was located north of Washington. It covered the area to be from the Pacific Ocean to western part of the Laurentide Ice Sheet in northern Montana (Pardee). Sometimes, these two ice sheets combine into large ice sheet having over 400,000 km of length. There are three main lobes associated to Cordilleran Ice Sheet, the Purcell lobe, the Okanogan lobe and the Puget lobe. The Purcell lobe moves southward through the Purcell trench in the northern Idaho. Then a finger of this lobe blocks the Clark Fork River creating an ice dam. The Clark Fork River flows northwest to the Columbia River. The blockage created an ice dam and the inland waters was called the Missoula Glacial Lake. It rises to about 610 km height and covered about the 10,000 square kilometers of land.

Ice dams are unstable structures because they are made of ice and it could melt anytime. The dam could fail in different ways. One is by flotation of the ice dam causing the water flow under it. The water creeps under the dam finding a hole in the dam causing the failure. Another is the water pressure that causes ice to melt. This pressure induces fiction against the wall deforming I and making it fragile.The water pressure induces friction which melts gradually, reducing the ice wall’s thickness and fall apart. The third one is natural subglacial tunnels which the waters enlarged through friction. The friction makes the tunnel larger making a hole in the ice dam causing the failure. The fourth one is the ice bergs which collided with the ice walls damaging them and causing them to fail.

 Whatever causes the ice dam to fail, the result is the same. There will be an outburst of water coming from the glacial lake called a jökulhlaup. A jökulhlaup causes the glacial lake flood. The Missoula Glacial Lake dam would fail when the water rises to approximately 600 m or about ninety percent of the thickness of the dam. Geologist calculated the volume for the ice dam to fail is 2000 to 2500 cubic km.

Pardee estimated the amount of water drainage of the Missoula Glacial Lake to be at the rate of 15.3 cubic kilometer per hour. And in 1973, another geologist estimated the drainage to be at the maximum rate of  62.5 cubic kilometers of water (Bjomstad).

Pardee studied the strandline present in Missoula, Montana which proves the location of the Missoula Glacial Lake. The highest of the strandlines is at the height of 1280 m which placed the water level in the Missoula Glacial Lake to be 635 m.

There are said to be two flood routes where the Missoula lake flood had flowed. One, the path was channel through the edge of the Pend Orielle Lake to the Spokane Valleys. The other route would be through the Pend Orielle River and spill over into the Little Spokane River (Pitman).

The Missoula Lake floods were probably the largest of all glacial lake floods. The question on how many times the filling of the dam, the failure of the dam and the flood is still subjected to further studies. Geologists used the rhytmites as basis of multiple floods. Rhytmites are sedimentary rocks or graded sediment which were laid in rhythmic beds. There is no estimated date how old these rhytmites are. It is because of the absence of enough dating materials. Rhytmites can be found around the area where the Missoula Glacial Lake was. There are other rhytmites which can be found in Washington and Oregon. Richard Waitt said that there are many other evidences that can tell the occurrence of the multiple floods. Like the tributaries of the Columbia River, one of the flood routes of the Missoula floods, where water spilled over its small channels containing sediments that were suspended in the flood waters. There are empirical evidences in these tributaries since geologists discovered sediment beds in the floors. These beds can be counted one by one. With these evidences Waitt concluded that at least forty floods occurred from Missoula Glacial Lake. Other evidences where found in the rhytmites all over Washington and Oregon.

J Harlen Bretz and Joseph Pardee spent most their career as geologists studying the Missoula Glacial Lake. Bretz started his research in 1922 when he led a field party of his students to the Channeled Scablands. These scarred land surfaces of the Columbia River basin (Channeled Scablands) were the subject of his field research. The research was done in seven seasons. On those seasons, he ventured the entire scablands by foot or by car. His research found mounded gravel bars which he realized that it can be done by glaciation or common erosion. The areas of the Long Lake Canyons, Dry Coulee and the Lenore Canyon were scarred surfaces. And no canyon with braided features was over the basalt surface. He presented papers which contains the detailed physiographic description of scablands and his hypotheses that a catastrophic flood made those features. The papers also contained that the flood might come from the Spokane area.

That was the time when the chief of Pleistocene geology in the U.S. Geological Survey sent Joseph Pardee to the Spokane area. He sent a report concluding that the scablands were due usual glaciation. Bretz visited the site where Pardee investigated. He found out that the glacial deposits which were contained in his report were actually flood bars. Here they had concluded the caused of the scarred surfaces of the Channeled scablands.

Dry Falls in Washington was one of the largest falls in northern America. It was created by the Missoula floods. Another feature which was created when glacial flood occurred is Wallula Gap. It slowed the water discharged to the Pacific Ocean.

Another mystery came that baffled geologists is whether Glacial Lake Missoula provided all or just some of the water that swept the northwest. Jim Shelden, a U.S. Forest Service geologist, said that a team of Japanese researchers modeled the eastern Washington’s Channeled Scablands in their supercomputer. They concluded that the volume of Glacial Lake Missoula, which was estimated to be 530 cubic miles, had lacked 25 percent of the amount of water to transform the scablands to what they are now (Pitman).

In Pitman’s article in 2004, Shelden said that the Japanese researchers took their best guess about the glacial and yet they had concluded that the Missoula Glacial Lake needed more water.

Many assumptions were made about where the rest of the water came from. Shelden suggested that it could have come from the Flathead Valley basin which was filled with ice at that period. Or from a volcano which erupted below the Cordilleran Ice Sheet. This was what other geologists believed.

UM geology professor David Alt also believed that the missing water came from the Flathead. He also says that “seiching,” or wave action, was another explanation. It created a splash when Glacial Lake Missoula broke through its dam and spilled into the shallower Glacial Lake Columbia.

The quest of finding the secrets of the Missoula Glacial Lake and its flood has not yet come to an end. Some geologists made some great contribution to search like J Harlen Bretz, Joseph Pardee, and Richard Waitt. But their theories have not yet been proven. More and more geologist all over the world joins this conquest to unravel the mysteries of the glacial floods. The clues have been revealed by the glacial floods but no findings had been foolproof. There is no certainty these geologists` postulate. Only one thing is for sure, the efforts of these geologists have been outstanding and yet the mysteries of the lake have not yet been uncovered.

Geologists still study the Glacial Lake Missoula and the Missoula Floods to bring more light to the true explanation of their existence. Thus, it will also be the key to some things that could only be explained through the events surrounding the Glacial Lake Missoula.


Bretz, J.H. “The Channeled Scablands of the Columbia Plateau.” J. Geology 1923. 31:617–649.

Oard, M.J. An Ice Age Caused by the Genesis Flood, Institute for Creation Research. El Cajon, California, 1990.

Pitman, Sean D. And The Great Scabland Debate. 2004.

Waitt Jr, R.B. “About forty last-glacial Lake Missoula jökulhlaups through southern Washington.” Journal of Geology 1980. 88:653–679.