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Glacial History


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In the summertime, especially in the late afternoon, the glaciers on Mount Shasta send meltwater down the stream channels at their bases. Much of the water is quickly absorbed by the volcanic substrate. However, if it has been especially warm for a continued period, or a summer thunderstorm adds to the meltwater, mudflows can form.

MUDFLOWS, also called debris flows or JÖKULHLAUPS (especially when volcanic activity warms things up), carry a cement-like mixture of volcanic ash and water combined with larger material, including boulders. The Whitney and Bolam glaciers on the northwest side of Mount Shasta and the Konwakiton glacier on the south side of Mount Shasta are the the glaciers notorious for producing mudflows. However, the Hotlum and Wintun glaciers have also produced numerous mudflows over the past several hundred years (Miller, 1980).

During the past one hundred years, there have been nine known mudflows from the Whitney-Bolam glaciers, with the most recent one occurring in 1997 (de la Fuente, 1999). Mud Creek has produced at least seven debris flows during the same period. The largest of the debris flows from Mud Creek, which occurred in 1924, 1926, and 1930 will be discussed further.

Konwakiton Glacier is one of the smaller glaciers located on Mount Shasta's southern slope just above Mud Creek. (Mud Creek Glacier curves around Peak 11267 above Shastarama Point.) Konwakiton Glacier has produced several mudflows in historical times (Finch and Anderson, 1928; Hill, 1984; Biles, 1989; Miesse, 1993) as well as during the last 10,000 years (Miller, 1980).

Mud Creek is especially vulnerable to flooding and mud flows because it is on the south side of the mountain and carves through 1,500 feet of ash deposits, which easily erode (Finch and Anderson, 1928). Mud Creek commonly overflows its banks, covering the railroad tracks and highway that run in an east-west direction on the south side of Mount Shasta. The town of McCloud is especially vulnerable to these glacial outburst floods.

The 1924 Mud Flow

News of the to-be-historical mudflow was of course known and talked about by the local residents from the earliest episodes. As the impact of this flow reached further afield, the story began to be told in outside newspapers. Following is a August 7, 1924 article from the Siskiyou News which attests to the spreading influence of the mudflows from Mud Creek.

Sacramento River Is Rather Milky

The 1924 mud flow from Konwakiton Glacier made front page news in the Redding Courier-Free Press six times during the months of August and September. The first article covering the story in this newspaper, on the front page, was:

Water of River Muddiest It Has Ever Been
Roads Washed Out by Rush of Water Down Mountain

One of the most interesting articles in the Redding Courier Free-Press was about a carcass found in glacial ice; but beware of accuracy, as the article in the next column is entitled "MARS HAS BIG AREA COVERED BY VEGETATION."

Party of Hikers Find Carcass of Mountain Sheep Among Blocks of Glacial Ice

It should be noted here that the "mountain sheep" later proved to be a pronghorn antelope (Hill, 1976). A little over two years later (September 22, 1926), the Mount Shasta Herald had an article about a skull of a plains antelope (Antilocapra americana) recovered from a glacier which was later donated to the Academy of Sciences in Golden Gate Park, according to a October 12, 1926 issue of Courier-Free Press.

News of this flood finally made it into the San Francisco Chronicle on August 19, 1924. Their explanation of events follows:

Shasta Glacier Mud Flow Cause
River Rise and Bad Roads Follow Obstruction

Another article appeared in the San Francisco Chronicle the following day, nestled between "Narcotics found in Hair of Suspect" and "Two Plans Given in L.A. Phone Problem" in the August 20, 1924 edition of the newspaper. The article reads as follows:

Fear of Flood at McCloud Quieted
Mud Flow Caused by Mt. Shasta Glacier

This particular summer the volume of water was heavier than usual and by August 12th flooding had occurred which "so buried the railroad tracks that traffic was stopped." The area around the RR tracks and highway were covered with material ranging from fine mud to "boulders weighing over a ton" and the material "was over a mile wide in places" (Finch and Anderson, 1928). Mount Shasta received an early snowfall on August 18th. The cold temperatures stopped the flooding temporarily. An eyewitness, J. M. Olberman, reported on August 20th, "The glacier was sloughing off in tons into the creek, great chunks coming down every few minutes with a rumble like that of distant thunder."

The San Francisco Chronicle later reported the following articles in rapid succession:

Shasta Glacier On New Rampage
Warm Weather Causes Mud River to Grow

McCloud Battles Mt. Shasta's Mud Torrent to Save Its Water Supply
With Railway Inundated and Main in Danger of Being Snapped, Situation Serious

Mount Shasta Mud Flow Halts
Melting Glacier's Torrent Suddenly Dries
McCloud is Saved Isolation

The reason that the mud flows had an affect on McCloud's water supply was that their source of water was Elk Spring, located at 4,200 feet elevation just to the east of Mud Creek. The pipeline which carried the water to the town crossed Mud Creek at about 3,920 feet before entering a reservoir a little further downhill.

News of the mud flow continued. By September 6th it had reached the Stockton Record which reported that "boulders float like feathers on mud stream". Several excellent photos and a nice map appear in this issue. By September 18th, news of the flooding had reached the front page of the San Francsico Chronicle with these bold headlines:

Terrific Roar of Collapse Startles Residents for Many Miles
Fear Expressed Damned-Up Waters May Overflow and Inundate Valleys
Even though Lassen erupted the following day, news regarding the recent problem made front-page headlines:

Cave-in Dams Flood of Lava, Glacier Mud
Sudden Cold Spell Sets Natural Formation, Saving McCloud from Torrent
Lake Forming on Mountainside as Snow Waters are Impounded

I have to wonder what McCloud residents thought about one of the last articles written about the 1924 Mud Creek debris flow when they read the following account printed in the Redding Courier Free-Press:

Mountain Takes on Brilliant Mantle of White;
End of Disturbance is Expected

By the end of the summer of 1924, the mud flow deposited 5.4 million cubic meters of mud which covered over 6 square kilometers on the south slope of Mount Shasta near McCloud (Miller, 1980). Untold amounts of mud flowed down the McCloud River and eventually into the Sacramento River, causing the Sacramento River to rise 4 inches early on in the episode according to an August 19th newspaper report from Redding. An interesting notion was presented in a September 25, 1924 article entitled "McCloud Mud Flow to be Fossil Bed" in the Siskiyou News. As the mud flow dries and hardens " that of rough concrete is evident from the nature of the deposit that thousands of animals, birds, reptiles, plants and trees caught in the flow will provide the material for a marvelous fossil bed."

In July of 1925 the U.S. Corps of Engineers undertook a study of the mudflow problem. At that time they stated that Konwakiton Glacier was 800 feet wide at its base and 100 feet thick. A waterfall, from the meltwater draining through the many moulins or vertical shafts at the downslope end of transverse fissures, poured forth from beneath the glacier through glacial portals. A west branch of the glacier also had a waterfall pouring forth from it. This study pointed out that future mud flows could not be prevented but that it was possible to divert the flows to the old bed of Elk Creek by constructing a diversion dam which would then divert the flows along a diversion training dike over to Kavinaugh Flats, an old alluvial cone (Hill and Egenhoff, 1976).

September 1924 Annotated Photo Album of Mud Creek Debris Flow
Courtesty of McCloud Fly Fishing Club

The 1926 Mud Flow

The 1926 mud flows were not as devastating as the 1924 mud flows. The McCloud River Lumber Company built a 100 foot dam to divert mud flows to Kavanaugh Flats. This method worked for awhile but by the end of July the mud was flowing down its old course. The Lumber Company succeeded in diverting the mud several times over the course of the summer. It is estimated that 1,300,000 cubic yards of mud were diverted onto Kavanaugh Flats via Elk Creek during the 1926 season while 700,000 cubic yards eventually made it into the Sacramento River (Hill and Egenhoff, 1976). An August 13, 1926 article in the Courier-Free Press stated that "well drillers in the city of McCloud, located at the base of Mt. Shasta, have found this mud flow formation at a depth of 300 feet..." The same article has several photos of the mud flow. The following July 29, 1926 article from the Courier-Free Press references the 1924 mud flow:

Mud Creek On Rampage Runs In Old Channel
Breaks Away From Dam Built Early in Season to Divert It Out Over Kavanaugh Flats Where Mud Was Deposited and Is Sweeping Boulders, Trees and Tons of Muck Down Its Former Course

Although 1928 was apparently not a notable year, an June 21, 1928 article in the Mount Shasta Herald shows the concern of the public, albeit in a light-hearted manner, in a segment of an article:

The 1931 Debris Flow

This event was larger than the 1924 and 1926 flows combined. An estimated 18,000,000 cubic yards of debris were diverted to Kavanaugh Flats (Hill, 1976). Although the 1924, 1926, and 1931 are the largest historical mudflows from Konwakiton Glacier, these are small compared to the debris flows of 600 and 1,200 years ago (Osterkamp, Hupp, and Blodgett, 1986).

There have been about three more mudflows since 1931 (Osterkamp, Hupp, and Blodgett, 1986) as well as the recent debris flow caused by the storms of December 1996 and January 1997. The Mud-Ash debris fan, composed of mudflows from Mud Creek and Ash Creek, is 300 km2 (Osterkamp, Hupp, and Blodgett, 1986).

Governmental aid at various levels were requested over the years to help divert mud flows away from McCloud. Several persuasive arguments were provided in various newspaper clippings between 1924 and 1934. In 1927 the Englebright Bill was put before Congress but failed. Finally, in 1936, a joint-governmental "dedication of Mud Creek Dam Project" was held. An October 8, 1936 article in the Mount Shasta Herald summarized the history of the Mud Creek diversion project.

In 1971 a 3,467 acre region on Mount Shasta's southeast slope was designated as a Research Natural Area by the U.S. Forest Service (Mount Shasta Herald, November 11, 1971). This study site will allow soil scientists, botanists, geologists, and others a chance to study soil and vegetation development on mudflows over time, as there are several dated flows in the area.

The Whitney Debris Flow

Meltwater flows from Whitney and Bolam Glaciers into Bolam Creek, Graham Creek, and Whitney Creek. The three streams merge into one (Whitney Creek) before crossing Highway 97. Occasional debris flows cross Highway 97 and are deposited in a debris fan 20 km2 in size which reaches all the way to Lake Shastina (Osterkamp, Hupp, and Blodgett, 1986). The Mount Shasta Vista subdivision is located on this debris flow. A 1985 article from the Siskiyou Daily News shows the outcome of building in a flood plain:

Melting Glaciers Blamed For Runoff
Flooding Hits Subdivision

Prior to the 1985 event covered in the newspaper article, there were at least five other mudflows from Whitney Creek during the first half of the 20th century. Since 1985 there have been three more debris flows in this region, with the latest occurring in 1997. The largest mudflow during the 1900s occurred in 1935. This mudflow, like the 1997 one, was triggered by a summer storm. In the case of the 1997 flow, the tropical storm Ignacio brought 4.4 cm of precipitation to Weed on August 19th (de la Fuente, 1999). The 1997 debris flow cut deeply into the deposits left by an earlier mudflow and carried this material downstream.

Air photo of Whitney Creek
Whitney Creek adjacent to a lava flow
Air photo by Linda Freeman, October 17, 1998

Satellite imagery from 1999 indicates the extent of the Whitney debris flow. In the following image, the northwest portion of Mount Shasta is located in the lower right section of the image. The center of the image is occupied by lava flows of varying composition and ages, with the Lava Park lava flow shown in bright green. Lake Shastina shows up as bright yellow. The Whitney and Bolam Creek mudflows flow diagonally from the mountain to the northwest. They are blue-violet in color and are located northeast and parallel to the bright green Lava Park lava flow. Notice that the mudlow extends all the way to the agricultural region to the northeast of Lake Shastina. Click on the image for a closer look.

ETM+ satellite image taken July 14, 1999 (Bands 1, 4, 7)
Enhanced Thematic Mapper Plus
July 14, 1999 (Bands 1, 4, 7)

The 1997 Whitney debris flow has been extensively studied by members of the United States Forest Service (de la Fuente et al., 1998; de la Fuente and Bachmann, 1999). They have produced several excellent maps and DEMs as well as made a video documentary. To get a feel for the power of a mudflow, you can watch a segment of the video.

Videoclip of August 1997 Whitney Debris Flow
Videoclip (MPEG) of Whitney Debris Flow, August 1997
Full video available for viewing at
U.S. Forest Service
McCloud Ranger Station
McCloud, California 96057
(530) 964-2184

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