Bretz, J Harlen

views updated May 29 2018

BRETZ, J HARLEN

(b. Saranac, Michigan, 2 September 1882; d. Homewood, Illinois, 3 February 1981),

glacial geology, origin of limestone caves, Earth science education.

J Harlen Bretz (“J” is his entire first name, not an abbreviation to be followed by a period) was the central figure in one of the most important controversies in the history of geology. In a series of papers in the 1920s and 1930s, Bretz formulated and defended the hypothesis that cataclysmic flooding during the last Ice Age produced the unusual landscape of the channeled scabland region of eastern Washington State. The controversy lasted until the 1960s and 1970s, by which time overwhelming field evidence combined with new understandings of flood mechanics, erosion, and sedimentation to convince most geologists that immense flooding was indeed the cause of the channeled scabland landscape.

Early Life. J Harlen Bretz was born on 2 September 1882, in Saranac, Michigan, to Oliver and Rhoda Bretz, on the family farm. His father dabbled in farming but worked mainly in a store (variety and furniture) and in an undertaking business, both of which he owned. The young J Harlen Bretz (his original given name was Harley) had intense interests in amateur astronomy and in exploring the natural environment around the family farm, including the nearby Grand River. He attended Albion College, where he studied biology and received an AB degree in 1905. At Albion he also met classmate Fanny Challis, who became his wife in 1906. Subsequently, as a high school teacher in Flint, Michigan, Bretz developed a strong amateur interest in glacial geology. He produced his first publication on the topic in 1907, and after later moving to Washington to teach at Seattle High School, Bretz’s hobby evolved into his profession. He organized his mostly self-financed field studies of glacial geology in the Puget Sound region into a PhD dissertation, which was awarded summa cum laude from the University of Chicago in 1913. His thesis advisors at Chicago were the renowned glacial geologists Thomas Chrowder Chamberlin and Rollin D. Salisbury.

Bretz was appointed assistant professor of geology at the University of Washington for the 1913–1914 term. He was not happy at the university, complaining of his department’s textbook and lecture methods and of the lack of attention paid to field studies. An urgent appeal from Salisbury to help with field-oriented teaching at the University of Chicago induced him to move there in 1915 at the starting rank of instructor, but by 1921 he had moved up to the tenured rank of associate professor. Bretz’s work in teaching geology field courses, however, soon brought him back to the Northwest, initially to the Columbia River Gorge between Washington and Oregon. In 1922 his summer field course for advanced students initiated a study of the channeled scabland landscape in eastern Washington.

Flood Hypotheses. Bretz formally presented his famous hypothesis in a 1923 paper, “The Channeled Scablands of the Columbia Plateau,” published in the Journal of Geology. He proposed that a huge late Pleistocene flood (now dated at about sixteen thousand years ago) emanated from the margins of the nearby Cordilleran Ice Sheet, which then covered much of western Canada, extending from Alaska down to Puget Sound and the northern parts of Washington State, Idaho, and Montana. Named the Spokane Flood for its then-presumed source area, this cataclysm neatly accounted for numerous interrelated aspects of the channeled scabland landscape. The immense volumes of floodwater, up to 200 meters (about 660 feet) deep, were recorded by high-level spillways that developed when preflood valleys were inundated beyond their capacities, inducing the floodwater to spill over divides from one valley to another. Over a region of about 150 by 200 kilometers (about 490 to 660 feet) this process joined various preflood valleys into an anastomosing complex of dividing and rejoining channels. (Anastomosing refers to an interlacing network pattern of branching and reuniting channels.) This phenomenally deep floodwater was moving fast enough to produce an unusual form of erosion in the basalt bedrock, called “scabland” erosion because of its jagged appearance. Bretz also interpreted great mounds of fluvial gravel in the scabland channels to be subfluvial river bars, deposited in somewhat slower-moving portions of the floodwater. The name “channeled scabland” was applied to the entire complex of features. Farther downstream the flood passed through the Columbia Gorge, then formed a huge gravel delta at the location of present-day Portland, Oregon, and finally passed on into the Pacific Ocean.

All this proved too much for the geological community of the time. At the 12 January 1927 meeting of the Washington (D.C.) Academy of Sciences, Bretz was invited to defend his “outrageous” hypothesis before an audience of uniformly skeptical scientists. His oral presentation was followed by six other talks, all of which were sharply critical of the flood theory. For the next few decades, despite Bretz’s continuing efforts, including twenty major papers on the topic, the geological community largely resisted the cataclysmic flood hypothesis. Among the many geologists who published papers opposing the Spokane Flood hypothesis, some of the best-known are Oscar E. Meinzer, Richard Foster Flint, James Gilluly, and William H. Hobbs.

Resolution of the controversy came gradually, initially with the recognition by Joseph Thomas Pardee of a plausible source for the huge amounts of floodwater. In the 1940s Pardee showed that the ice-dammed Pleistocene glacial Lake Missoula, holding about 2,500 cubic kilometers (600 cubic miles) of water, formed in northern Idaho and western Montana and subsequently drained very rapidly to the channeled scabland. Eventually, the accumulating field evidence became overwhelming, particularly when Bretz and others synthesized new data obtained by the Bureau of Reclamation during the development of the Columbia Basin Irrigation Project in the 1950s. Especially important for convincing the skeptics was the discovery that giant current ripples cap many of the scabland gravel mounds that Bretz had correctly interpreted in the 1920s to be river bars. Resembling the relatively tiny ripple marks that form along the sandy bottoms of active rivers, the giant scabland ripples occur in trains of twenty or

more, with individual ripples of up to 10 meters (some 33 feet) in height and 100 meters in spacing. Instead of sand, these ripples are composed of flood gravel and boulders up to a meter in diameter. By the 1960s and 1970s, as this evidence mounted and as advances occurred in the understanding of the physical processes of cataclysmic flooding, Bretz’s bold hypothesis came to be almost universally accepted.

The debates of the 1920s and 1930s over the origin of the channeled scabland are important to geology for methodological reasons. The prolonged nature of the Spokane Flood controversy arose in part because of the adherence of many geologists to substantive and epistemological notions of uniformitarianism, a principle that was erroneously thought to underpin their science. According to the most common, mistaken applications of the uniformitarian principle, cataclysmic processes, such as those responsible for the origin of the channeled scab-land, were considered to be unsuitable topics for scientific investigation. This doctrine had originally arisen with Charles Lyell (1797–1875), who used it to argue against proposals in the early 1800s that catastrophic processes

(some of them biblical) were important to consider in understanding Earth’s history. To counter this presumption of uniformitarianism, Bretz could provide only meticulously described field evidence for those willing to seriously consider it. The eventual triumph of his hypothesis, against its initially antagonistic reception, set the stage for the resurgence of a new kind of geological catastrophism, which is most prominent in the new understanding of the role of impact cratering on Earth’s history.

Work in Greenland. After a decade of near-continuous research on the channeled scabland, Bretz turned to other studies, beginning with participation in the Louise A.Boyd Expedition to East Greenland in 1933. Work on the surficial geology of the Chicago region led to two monographs. These outline ingenious analyses of the draining of Glacial Lake Chicago, a predecessor of modern Lake Michigan. From 1938 to 1961 much of Bretz’s attention was devoted to studies of the origin of limestone caverns.He argued eloquently for the origin of many cave features by processes of groundwater circulation below the water table. His cave studies in seventeen U.S. states, Mexico, and Bermuda placed physical speleology on a firm scientific basis. Bretz’s most extensive cave survey was his book, Caves of Missouri, published in 1956. His insights and energy were important to the late-twentieth-century resurgence of karst geomorphic and hydrologic studies in the United States.

While a faculty member at the University of Chicago from 1915 to 1947 and in subsequent semiretirement, Bretz supervised the field geology training of more than three hundred graduate students, including the future geological luminaries M. King Hubbert, William C. Krumbein, Francis P. Shepard, and Hakon A. Wadell. His teaching excellence, employing the Socratic method, was renowned among all the program’s graduates and recognized in 1959 by the Neil Minor Award for teaching excellence from the National Association of Geology Teachers.

After his formal retirement from the University of Chicago, “Doc” Bretz (as he was known to students and colleagues) continued occasional work in association with the geological surveys of Illinois, Missouri, and Washington. With C. Leland Horberg in the 1940s and 1950s, Bretz published innovative research on the genesis of rock-like calcium carbonate encrustation in caliche soils. His 1965 monograph, “Geomorphic History of the Ozarks of Missouri,” stands as classical analysis of landscapes. In the 1970s and 1980s, new discoveries of scablandlike landscapes in other parts of Earth and, surprisingly, on the planet Mars, all were being explained by cataclysmic flood processes, much in the same manner that Bretz had first outrageously proposed in 1923.

At age ninety-seven, in recognition of a lifetime of scientific achievements spanning more than seventy years, J Harlen Bretz was honored in 1979 with the Penrose Medal, the highest award of the Geological Society of America. In accepting the award Bretz gave the following assessment of his major research accomplishments: “Perhaps I can be credited with reviving and demystifying legendary catastrophism and challenging a too rigorous uniformitarianism” (1980, p. 1095).

BIBLIOGRAPHY

The J Harlen Bretz papers (25 boxes, 12.5 linear feet) are housed at the Special Collections Research Center, University of Chicago Library, 1100 East 57th Street, Chicago, Illinois 60637. The archive contains many of Bretz’s writings from 1905 to 1977. There is no complete bibliography of all published works.

WORKS BY BRETZ

“Glaciation of the Puget Sound Region.” Washington Division ofMines and Geology Bulletin 8 (1913): 1–244. The published version of Bretz’s PhD dissertation.

“The Channeled Scablands of the Columbia Plateau.” Journal ofGeology31 (1923): 617–649.

“Geology and Mineral Resources of the Kings Quadrangle.” Illinois State Geological Survey Bulletin 43 (1923): 205–304.

“The Spokane Flood beyond the Channeled Scablands.” Journal of Geology33 (1925): 97–115, 236–259.

“The Channeled Scabland of Eastern Washington.” GeographicalReview 18 (1928): 446–477.

“The Grande Coulee.” American Geographical Society SpecialPublication 15 (1932): 1–89.

“Physiographic Studies of East Greenland.” In The Fiord Region of East Greenland, edited by Louise A. Boyd. New York: American Geographical Society, 1935.

“Geology of the Chicago Region: Part 1, General.” IllinoisGeological Survey Bulletin65 (1939): 1–118.

“Vadose and Phreatic Features of Limestone Caves.” Journal ofGeology50 (1942): 675–811

. “The Stages of Lake Chicago: Their Causes and Correlations.” American Journal of Science 249 (1951): 401–429.

“Geology of the Chicago Region: Part 2, The Pleistocene.” Illinois Geological Survey Bulletin 65 (1955): 1–132.

“Caves of Missouri.” Missouri Geological Survey and WaterResources Report 39 (1956): 1–490.

With H. T. U. Smith and George Neff. “Channeled Scabland of Washington—New Data and Interpretations.” Geological Society of America Bulletin 67 (1956): 957–1049.

“Washington’s Channeled Scabland.” Washington Department ofConservation,Division of Mines and Geology Bulletin 45 (1959): 1–57.

“Bermuda: A Partially Drowned, Late Mature Pleistocene Karst.” Geological Society of America Bulletin 71 (1960): 1729–1754.

“Geomorphic History of the Ozarks of Missouri.” MissouriDivision of Geological Survey and Water Resources Report 41 (1965): 1–147.

“The Lake Missoula Floods and the Channeled Scabland.” Journal of Geology77 (1969): 505–543.

“Introduction.” In The Channeled Scabland: A Guide to theGeomorphology of the Columbia Basin, edited by Victor R. Baker and Dag Nummedal. Washington, DC: National Aeronautics and Space Administration, 1978.

“Presentation of the Penrose Medal to J Harlen Bretz: Response.” Geological Society of America Bulletin, Part II, 91 (1980): 1095.

OTHER SOURCES

Baker, Victor R. “The Spokane Flood Controversy and the Martian Outflow Channels.” Science 202 (1978): 1249–1256.

——, ed. Catastrophic Flooding: The Origin of the ChanneledScabland. Stroudsburg, PA: Dowden, Hutchinson and Ross, 1981. Editorial commentary and reprinted papers outline the Spokane Flood controversy, emphasizing Bretz’s role and the relevant historical and scientific contexts.

———. “The Spokane Flood Debate and Its Legacy.” In Geomorphic Systems of North America, edited by William L. Graf. Boulder, CO: Geological Society of America, 1987.

———. “Joseph Thomas Pardee and the Spokane Flood Controversy.” GSA Today 5 (1995): 169–173.

Baker, Victor R. and R. C. Bunker. “Cataclysmic Late Pleistocene Flooding from Glacial Lake Missoula: A Review.” Quaternary Science Reviews 4 (1985): 1–41.

Victor R. Baker

Complete Dictionary of Scientific Biography

Bretz, J Harlen

views updated May 23 2018

Bretz, J Harlen

American Field Geologist 1882–1981

J Harlen Bretz is best known for his hypothesis that floods of enormous volumes once swept across southeastern Washington and on out the Columbia River Gorge to the Pacific Ocean. Bretz was widely criticized by his contemporaries for his "outrageous hypothesis" while continuing to use his own observations, not popular opinion, to develop his ideas. Like a detective, Bretz gathered as many clues as he could and reached what he believed to be the best solution to the geologic puzzle of the Missoula Floods.

A Pioneering Theorist

Born in Michigan in 1882, Bretz showed an early interest in science, and in college obtained a biology degree. While teaching high school biology in Seattle, Washington, he became interested in glacial landforms in the Puget Sound area that were formed during the most recent glacial period (ending about 10,000 years ago). He spent many of his weekends in the field taking careful notes about the landforms that he saw. Many of his observations were published in scientific journals.

In 1913, Bretz earned a Ph.D. in geology at the University of Chicago and began studying landforms in eastern Washington state that seemed to defy explanation by traditional geologic theories. These landforms included incredibly high dry falls perched well above the current river level; huge potholes, some 50 to 100 meters (150 to 330 feet) across; huge 200-ton boulders, that because they differed markedly in mineralogy from the surrounding bedrock must somehow have been transported to their current locations; and gigantic gravel bars that were the size of hills, hundreds of meters long and tens of meters high. Bretz's experience in the glacial terrain of the Puget Sound offered him an important perspective. He recognized many of these features were simply gigantic replicas of the same smaller-scale features that he had seen time and time again in glacial streams and outwash areas: the depositional and erosional products of meltwaterfed streams during the last ice age . Clearly, however, the volume of floodwater required to produce these gigantic landforms would have had to have been prodigious.

The prevailing theory regarding the origin of Earth's landscape was Uniformitarianism, which stated that all landforms on Earth's surface were produced by ordinary geologic processes—for example, stream erosion and deposition—acting over immense geologic time. These processes were deemed capable of producing deep canyons such as the Grand Canyon of the southwestern United States. The contrasting theory, Catastrophism, held that landforms on the Earth resulted from catastrophic events, such as huge earthquakes and biblical floods. To many geologists in 1920, Bretz's flood hypothesis was too close to a biblical interpretation.

Bretz endured nearly four decades of doubt and ridicule by other geologists of the time, in part because Bretz was unable to offer a reasonable explanation for the source of the huge amounts of water that would have had to have been suddenly and catastrophically released across eastern Oregon. Bretz's work was finally vindicated, however, when another geologist, Joseph Pardee, found evidence of a former huge lake (Lake Missoula) in western Montana that was formed when the Clark Fork River had been dammed by a glacier. The lake had rapidly drained when the dam failed, allowing enormous amounts of water to flood eastern Washington (see discussion below).

Only in the 1950s and 1960s was Bretz's hypothesis regarding the Missoula Floods accepted and his contributions recognized. In 1979, the Geological Society of America awarded J Harlen Bretz, then 96 years old, the Penrose Medal, the highest national geological award for his contributions to geological knowledge.

The Modern View of the Missoula Floods

It is now widely accepted that the Missoula Floods occurred when vast amounts of water rushed across approximately 7,800 square kilometers (3,000 square miles) of southeastern Washington, scouring soil from the surface, gouging out blocks of bedrock, and turning river valleys into river channels. Water levels were so high that the water overflowed the top of the Columbia River Gorge in several places, and reached a depth of approximately 100 meters (328 feet) where present-day Portland, Oregon is located (see the figure). The evidence for the Missoula Floods was compiled by Bretz, who recognized the following characteristic features:

Dry falls, 180 meters (600 feet) above the present Columbia River level, over which water once cascaded;
Huge potholes, requiring enormously turbulent water;
Gigantic boulders, up to 200 tons, transported from eastern Washington to Oregon; and
Enormous gravel bars, 90 to 120 meters (300 to 400 feet) high.

Lake Missoula was formed by the glacial damming of the Clark Fork River at the end of the last ice age (approximately 10,000 years ago). Ancient lake beaches perched on mountains 640 meters (2,100 feet) above the present-day valley floor indicate the lake's size. When the dam failed, Lake Missoula waters roared out at the phenomenal rate of approximately 40 cubic kilometers (9.5 cubic miles) per hour, almost 200 times the Mississippi River's flow rate at flood stage. The rapid draining is indicated by huge ripple marks, 15 meters (50 feet) high and 150 meters (500 feet) apart, on today's valley floor. The damming and flooding cycle repeated itself as many as 40 times during the last ice age.

see also Glaciers and Ice Sheets; Ice Ages; Stream Erosion and Landscape Development.

Dennis O. Nelson