Geology

Gilbert, Grove Karl

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Grove Karl Gilbert, about 1910. Photo courtesy US Geological Survey

Grove Karl Gilbert (or "GK" Gilbert, 1843-1918) was one of the leading geologists of the late 1800s and early 1900s and, compared to his contemporaries in the field of geomorphology, he is the one with the greatest influence on current thinking.

Early Years

Gilbert was born in Rochester, New York. Little is known about his mother, but his father was a portrait painter. The close-knit family lived frugally and spent evenings in intellectual pursuits such as group poetry writing, riddle solving and reading aloud. He sought out such an enriching environment his whole life.

GK attended public school some, but because of poor health, much of his education came from his family. (It’s not clear what his health problems were.) He was a voracious learner who spent his entire life as a studious, hardworking, mild mannered and nice person. He attended Rochester University, where languages, logic, rhetoric and mathematics dominated the classical education prevalent at the time. But he also was well educated in Newtonian physics and learned a bit of geology and botany, as well. His family insisted that, while there, he improve his health with vigorous outdoor exercise which helped prepare him for the arduous field work in his future.

Gilbert graduated at age nineteen, just as the Civil War was beginning. His uncertain health may have prevented him from being drafted and he apparently had no interest in enlisting. Instead, he tried to pay off college debt by becoming a teacher to farm children in Michigan. Unable to discipline his students, he failed at this job and quit before completing his first year.

In 1863, he apprenticed to “Cosmos Hall” back in Rochester. Explorers around the world were collecting natural history specimens, like fossils and minerals, and Cosmos Hall processed and sold them, mostly to museums. His office work and occasional field expeditions helped him develop a knowledge and love of geology. On an expedition near Albany, New York to excavate a mastodon skeleton, the leader got injured and Gilbert took over the project. He later returned to the site and attempted to understand changes to the landscape since the mastodon lived there. This included estimating the upstream migration rate of the local waterfall. This study involving the environmental reconstruction of past landscapes began the path he followed in his career in geology.

After five years at Cosmos Hall, Gilbert sought a job that would train him better to be a geologist. He became a volunteer assistant at the Geological Survey of Ohio. Because he was not a citizen of the state, he could not be an official employee, but as a volunteer, he received a stipend for his living expenses. John Strong Newberry, one of the leading American geologists of the time, led the Survey. Newberry taught GK much and introduced him to other leading luminaries in American science. The main focus of the Survey was to aid industry, mostly through mining studies, and agriculture, mainly through mapping soils and related resources. But purely scientific topics, like paleontology and glacial history, were pursued as well. Gilbert learned mapping techniques, stratigraphic interpretation, and how to search for valuable mineral deposits. These skills added to those he learned at Cosmos Hall, like classification techniques.

Wheeler Survey

After two years in Ohio, Newberry recommended Gilbert as a civilian geologist for the U.S. Army’s Geographical Survey West of the 100th Meridian, headed by Lt. George Wheeler. In the first field season, 1871, the Wheeler Survey travelled over 10000 kilometers. They started in Nevada and explored desert lands in Eastern California, including a crossing of Death Valley (hottest place in the Western Hemisphere) in July. They arduously hauled boats up the Colorado River into the lower reaches of the Grand Canyon and crossed Arizona from the Canyon to Tucson. The Survey’s main objective was mapping, but Gilbert noted the geology as they travelled. The second and third field seasons involved less travel and, for Gilbert, more carefully done geologic investigation in Utah, New Mexico and Arizona.

Gilbert spent the fourth and final year with Wheeler mostly in Washington, DC, writing reports on the field work. The two geological regions he studied were the Basin and Range and the Colorado Plateau. The Basin and Range is made of many parallel mountains and valleys that had been interpreted as anticlines and synclines, similar to the Appalachian Mountains in the Eastern US. Gilbert showed that the landscape was created by parallel faults with mountains being upthrust and valleys dropping down between them. He returned to this topic occasionally for the rest of his life and eventually all geologists accepted his interpretation of the evidence. On the Colorado Plateau, he began to think of landscapes not, like most geologists, as the current stage in a long historical evolution but, as physicists might see them, as situations tending toward a balance between competing forces.

Another theme he would return to in later studies began with his work for Wheeler. While glaciers covered the northeastern U.S. during the ice ages, Gilbert saw that the West was much wetter, with large lakes filling what now are desert valleys.

Powell Survey

In Washington, Gilbert formed friendships with fellow scientists and became part of the scientific establishment in the city. He had met John Wesley Powell in Utah; Powell led another of the Western Surveys and he and Gilbert became close friends in Washington. Gilbert quit the Wheeler Survey and began to work for Powell. At about the same time, he met Fannie Porter, whom he met at a dance at Powell’s home. They soon were married. By this time, Gilbert was a well-respected geologist and Powell’s leadership fit GK’s style and temperament like a glove.

Gilbert began work for Powell in 1875, and spent most of his field time the first few years in Utah. He was able to study geology at his own pace, though over time he became increasingly responsible for overseeing much of the survey work while Powell dealt with politicians in Washington.

Powell, Gilbert and geologist Clarence Dutton, also a member of the Powell survey, proved to be three intellectual giants whose synergistic scientific output explained the geology of the Colorado Plateau and, in so doing, greatly advanced the science of geology.

One of Gilbert’s greatest contributions to science is his monograph on the Henry Mountains in Utah. In it, he explained a new form of mountain building and developed a theory for how streams shape the landscape. Gilbert spent one week in the Henrys in 1875 and two months in 1876. Most of his time was spent mapping, but the ideas for his monograph were gelling in his mind. For several days in 1876, it rained too much for mapping, so Gilbert sat in his tent and fleshed out his ideas in his notebook. Upon returning to Washington, he spent several months writing the official report, which was published in 1877.

Gilbert determined that magma rose through the crust but had insufficient pressure to reach the surface. When it could no longer rise, it spread sideways and pushed the overlying rock up to form a mountain dome. The intruding rock, called a laccolith, slowly solidified and the dome stopped growing. Unlike most geologists of the time, Gilbert explained the landscape from the perspective of physics, engineering, and mathematics. Several other geologists in the Western Surveys had similar thoughts on laccoliths and mountain formation, but Gilbert developed the theory much more fully than any of the others.

Wholly original to Gilbert was his explanation of how streams erode the landscape, using the Henrys as an example but presenting concepts applicable everywhere streams flow. He presented what came to be known as the “Theory of the Graded River,” where “grade” refers to the steepness of the stream channel. Streams carry a certain amount of water down a certain slope angle and these determine the energy of the flowing water. The movement of sediment in the stream uses some of the energy and if there is energy left over, the stream will erode the bed of the stream. But by eroding the bed, the slope decreases and, hence, the energy decreases until erosion stops because there is no extra energy. On the other hand, if more sediment is dumped into the stream, from tributaries or washed off hillsides, than it has energy to move, some will be deposited. This deposition increases the slope angle and energy increases until the stream can carry all of the sediment. In both cases, the stream adjusts its slope until it has the right amount of energy to carry its sediment load and once this equilibrium situation is achieved, the stream will remain unchanged. In the real world, the sediment load and discharge of the stream vary over time, so streams rarely will truly be in equilibrium but are tending toward an equilibrium condition which itself changes over time.

If a landscape is comprised of one rock type evenly distributed, then steeper areas will erode more quickly than less steep parts and, given enough time, the landscape would erode to a flat, uniform surface. But, most landscapes are made of a variety of rocks with varying resistances to erosion, so stronger rocks tend to form steeper parts of the landscapes while weaker rocks are worn away to create the flatter parts. Like the streams, the whole landscape is tending toward a balance between the forces of erosion and the resistances to it. While erosion continues, the basic shape of the landscape can remain relatively unchanged for long periods of time.

Report on the Geology of the Henry Mountains introduced new and highly original concepts and, so, was not immediately accepted. American geologists regarded streams as fundamentally important in landscape creation, but most Europeans at the time saw streams playing a minor role. It was several decades before his ideas were generally accepted in Europe, while acceptance in the US was quicker. Gilbert had established himself as a well-respected field geologist and a world-class theoretician.

US Geological Survey

There were four Western Surveys, run by Powell, Wheeler, Clarence King and Ferdinand Hayden. These were merged into the US Geological Survey in 1879, under the leadership of King. Gilbert was put in charge of the Great Basin and he set out to understand Lake Bonneville, a huge Pleistocene lake in northwestern Utah. The Great Salt Lake today is a small remnant of the lake that existed during the last ice age. It was clear by alternating deposits of lake sediments and desert alluvial fans and salt deposits that the large lake basin had filled and dried multiple times and Gilbert set out to understand how this happened and how it helped shape the landscape. Gilbert led a team that mapped the region while he investigated the processes acting on the lake, based on relict features like beaches and deltas now on desert mountainsides and valley floors.

He spent three field seasons in Utah, going home to Washington each winter. But before he could start a fourth, King resigned. Powell became Director of the USGS while continuing to lead the Bureau of Ethnography for the Smithsonian Institution. Powell needed Gilbert in Washington and left him to do much of the day-to-day running of the Survey. For twelve years, Gilbert rarely left Washington and the completion of his Lake Bonneville work was a long, drawn-out process. He held the titles of “Senior Geologist” and, later, “Chief Geologist” of the USGS.

caption Geographer Willard D. Johnson in Utah, mapping for Gilbert, 1901. Photo courtesy US Geological Survey.

Gilbert published short articles on the Lake Bonneville work, but he did not draw it all together until he published a 400-page monograph, Lake Bonneville, in 1890. Gilbert advanced the understanding of shoreline processes and how beaches are formed by waves. He reasoned that the wetter, “pluvial,” periods in the West were caused by the same climatic changes that led to the ice ages in the East. The lake left two main shorelines that once were as flat as a lake surface but now are warped. Gilbert showed that the weight of the huge lake depressed the crust beneath and when the water disappeared, the crust rebounded unevenly. (Others were finding similar “isostatic rebound” in glaciated regions, like the Great Lakes in the US and Scandinavia.)

While most geologists were chronicling the history of regions, Gilbert was interpreting landscapes as the product of physical forces, like waves, acting on the land. Lake Bonneville, like the Henry Mountains before it, introduced many new ideas to geology and showed Gilbert to be a giant in the discipline.

 

An example of Gilbert’s research while confined to Washington is his study on the origin of craters on the moon. Through a series of experiments, including the firing of lead balls into mud to observe the resulting crater, and comparisons between volcanic and meteoric craters on earth, he concluded that the moon’s surface was not volcanic. Instead, it was shaped largely by impacts. He concluded that Earth originally had a ring of debris, much like Saturn, and these coalesced over time to form the moon. On this later point, he was later shown to be wrong, but the meteoric origin of the craters has been confirmed. Through this study, he also began the now widespread discipline of planetary geology.

GK and Fannie had a daughter, Bessie, and two sons, Archibald and Roy. Bessie contracted diphtheria in 1883 and died at age six. While the parents grieved, they, too, came down with the disease. They recovered, but slowly. Fannie became an invalid and her health deteriorated until her death in 1899. The boys spent much time away from home, including boarding schools and time with Gilbert’s brother in New York. Both worked for their father some as adults and, while Gilbert was not especially close to his sons, they kept on good terms.

Powell resigned from the USGS in 1894, but Gilbert remained with the service. He declined several invitations to become a professor, presumably preferring research to a combination of research and teaching.

caption Gilbert in Colorado, 1894. Photo courtesy US National Academy of Sciences.

Hydraulic mining began in California’s Sierra Nevada in the 1850s. Powerful water cannons blasted away hillsides and gold was removed from the debris as it washed away. By the 1870s, so much sediment was moving down rivers that their channels filled and surrounding farms and towns were flooded. It became clear that the debris would eventually fill in much of San Francisco Bay. A court order stopped the hydraulic mining, but the mining corporations involved asked the federal government to make it legal again. In 1904 President Roosevelt asked the USGS to study the problem and Gilbert was given the job. His investigation had two related parts. The first was an experimental study of how sediment is moved by streams and the second was a field evaluation of the problem. In the course of this research, in 1909, Gilbert had a stroke which greatly limited his physical activity for the rest of his life. After a few years of recuperation, he returned to a slowed pace of work and completed the hydraulic mining research.

“The Transportation of Debris by Running Water” was published in 1914. Gilbert set up a laboratory in Berkeley with a flume to measure sediment transport under various conditions. After designing the experiments, he left most of the work to his assistants. He immersed himself in the literature of fluid flow, mostly work done by physicists and engineers in Europe. He interpreted his experimental results with the prevailing theories and presented an exhaustive treatise of sediment transport.

The field portion of his hydraulic mining work was, for Gilbert, a perfect test of the graded river theory he outlined in his Henry Mountains work decades before. If streams tend toward an equilibrium, where they have just enough energy to transport the sediment they receive, then the Sierra streams under consideration were drastically thrown out of equilibrium by the mining debris. “Hydraulic-Mining Debris in the Sierra Nevada” was published in 1917.  In it, he predicted, with reasonable accuracy, how long after the mining stopped, the streams would return to their pre-mining equilibrium elevations and slopes. He also outlined a framework for viewing watersheds as coherent systems affected by both natural laws and human actions. It took decades before such thinking was commonly used in environmental studies. Gilbert’s work provided the justification for permanently outlawing large-scale hydraulic mining in the region.

While in California, Gilbert met Alice Eastwood, a botanist and fellow Sierra Club member.  The two fell in love, planned to marry and even made plans to raise Gilbert’s grandson after his daughter-in-law died. But while visiting his sister in Michigan, he fell ill. Several weeks later, Gilbert died of heart failure, a few days before his seventy-fifth birthday.

In addition to the research work discussed above, Gilbert made important contributions to many areas of earth science. These include glacial geomorphology and glaciology, earthquake prediction and evaluation of earthquake damage (he was present for the 1906 San Francisco Earthquake), coastal geomorphology, and groundwater.

Another contribution to earth science is Gilbert’s philosophical positions on how geologists should contribute to knowledge. To reduce personal attachments to theories being tested, he advocated for researchers to generate  “multiple working hypotheses,” and test all of them at the same time. The one that best fits the evidence is then assumed to be correct. An important source of hypotheses is analogous situations. For example, physicists and engineers knew much about how a beam flexes when weight is added and then removed. Perhaps, he hypothesized, Earth’s crust under Lake Bonneville flexed in a similar way as the basin filled and emptied. A scientist should be both theoretician and careful observer and the best scientists are those who can generate the best hypotheses and design the best tests. (Gilbert’s philosophical ideas overlapped with T. C. Chamberlin, another leading figure in geology at the time.)

In a memorial to Gilbert, USGS geologist W. C. Mendenhall praised him:

In sheer balance of mental power, Gilbert was probably unsurpassed by any geologist of his time. Fundamental among the qualities of his mind were self-knowledge and self-control. These qualities he possessed in a degree equaled by few. That mind which he knew and controlled so well was a quiet, efficient, powerful instrument, which functioned perfectly. Thus he was the very antithesis of the brilliant, temperamental, erratic genius. He recognized both his powers and his limitations, and did not undertake that which he was not equipped to do.  (Quoted in Pyne, 1980, p. 105)

 

Scholarly Impact

Gilbert received many accolades. He was a member of the National Academy of Science, and was elected president of many scholarly organizations, including the Geological Society of America in 1892 and again in 1909, the American Association for the Advancement of Science in 1899, the National Geographic Society in 1904, and the Association of American Geographers in 1908. In 1900, he was awarded the prestigious Wollaston Medal from the Geological Society of London. Much to his delight, he also belonged to less formal groups like the “Great Basin Mess,” a group at the USGS that regularly met for lunch and discussion.

Gilbert was highly respected during his lifetime, but his influence on geomorphology was limited for decades after his death. The study of landforms for the first half of the Twentieth Century, especially in the English speaking world, was dominated by the qualitative study of landscape change over millions of years. This approach, known as the Cycle of Erosion, is most closely associated with William Morris Davis, who dominated the discipline until his death in the 1930s. (Davis, however, wrote a 300 page biography of Gilbert, extolling his life and works.) After the Second World War, geomorphologists sought a different way to study landform dynamics and Gilbert’s work provided both insight and inspiration. Research became more physically based and quantitative, like his hydraulic mining work, emphasized systems concepts that drew heavily from his Henry Mountains work on equilibrium, and put more effort into explaining landscape changes rather than merely chronicling them, like his Lake Bonneville studies. The “G.K. Gilbert Award” for outstanding research is a testament to the respect given him many decades after his death is. This award is given independently by three separate organizations, The Association of American Geographers (first awarded in 1983), The Geological Society of America (also 1983), and The American Geophysical Union (2010).

 

Further Reading

Davis, William Morris, 1927. Biographical Memoir of Grove Karl Gilbert, 1843-1918. National Academy of Science Volume XXI Fifth Memoir, 303 p.

Pyne, Stephen J., 1980. Grove Karl Gilbert: A great engine of research. Austin, University of Texas Press, 306 p. [This book is the primary source of material for the information above.]

Yochelson, Ellis L., ed., 1980. The Scientific Ideas of G. K. Gilbert: An assessment on the occasion of the centennial of the United States Geological Survey (1879-1979). Geological Society of America Special Paper 183, 148 p.

Glossary

Citation

Lee, J. (2013). Gilbert, Grove Karl. Retrieved from http://www.eoearth.org/view/article/51f7dc470cf2b3d06e25aa6f