The principle of uniformitarianism states that natural laws and processes (chemical and physical) operating today have always operated in the past but not necessarily at the same rate or intensity. So, these forces and processes we can observe today are the same that shaped the Earth throughout history.
James Hutton came up with the uniformitarianism principle or doctrine for the first time. Later, Charles Lyell popularized, advocated, and promoted it using the phrase ‘present is the key to the past,’ a reason why some people attribute it to him. However, it was not until 1832 that William Whewell coined the term uniformitarianism.
Today, we will elaborate on the principle of uniformitarianism, giving you its meaning, significance, and historical background, including the view of Charles Lyell and James Hutton. We will also talk about uniformitarianism from a modern geologic point of view, something some geologists call actualism, why it is important or its relevance, and a lot more.
Historical background
To understand the principle or doctrine of uniformitarianism, here is some historical background:
1. James Hutton uniformitarianism view
Earlier scientists thought similarly, and some concluded that the Earth was very old. However, James Hutton (1726–1797), a Scottish geologist, farmer, physician, and naturalist, was the first person to express or propose the theory or ideas of what would later be known as the doctrine or principle of uniformitarianism.
He published his ideas in the Theory of the Earth with Proofs and Illustrations in 1795, based on simple and logical explanations of his observations. Hutton looked at some geological processes happening and features created. He then used what he saw to explain the formation of ancient rocks that bore the same features, i.e., what is happening now can explain the Earth’s history.
One of Hutton’s evidence or examples of uniformitarianism was when he saw how waves acting on shores created ripple marks. Later, he found rock strata near Edinburgh with ripple marks. Using his earlier observation, he concluded the rock strata with ripple marks were shoreline deposits by an ancient sea and inferred that there used to be a sea in that area but now a grazing place.
Also, by observing the Scottish coast, Hutton concluded that various very slow processes like weathering, erosion, the action of waves, sediment transportation and deposition, and volcanism, given time, will sculpt the Earth – create different geological structures or features we see, just like the catastrophic ones.
Hutton saw the Earth as dynamic and cyclic, not static, i.e., it had calmer times of continent erosion, sediment transportation and deposition under the sea, and upheaval time of land uplift later were ongoing, complete cycles. He concluded that his results showed “no vestige of a beginning—no prospect of an end” notes (Kusky & Cullen, 2010), and rock records had evidence of many cycles of mountain building and erosion.
The most important implication of Hutton’s ideas was that Earth had a long, unimaginable history or geologic timeline since the various processes that sculptured the Earth were slow. It must take a long time to create and destroy landscapes, i.e., eroding a continent and depositing sediments in the sea to form rocks under the sea before an uplift. However, he didn’t talk about the age of the Earth or how long cyclic erosion, sedimentation, and lithification is.
Hutton’s idea on a long geologic time contradicted a reputed scholar, James Ussher, Archbishop of Armagh, Primate of all Ireland noted, that the Earth was created in 4004 B.C.E. and was less than 6000 years old.
Unfortunately, Hutton’s ideas didn’t get popular. Why? Because, at that time, catastrophism was popular, natural conservative geologists didn’t want to abandon their Biblical creation account, and he was not a good writer. Also, his ideas were poorly disseminated, meaning some people didn’t understand them well.
2. Charles Lyell’s uniformitarianism concept
Later, a Scottish geologist, Charles Lyell (1797-1875), explained and advocated/popularized/promoted the principle of uniformitarianism through his Principles of Geology book in the 1830s. He considered the book a guiding principle in geology, influencing many geologists to shift from catastrophism to uniformitarianism.
He had his uniformitarianism field evidence examples of sea rising/falling, volcanoes lying on top of older rocks (Mt. Etna), erosions causing valleys, etc., and fossil records, some of which pointed to the Earth was indeed old.
To Lyell, uniformitarianism meant uniformity in present and past geological processes with uniform gradual rates of change. Put in another way, geologic processes and natural laws operating present on Earth also operated in the same manner in the past and at the same intensity and rates. This he summarized with the aphorism ‘the present is the key to the past.’
Therefore, these forces of nature that act slowly, gradually, and at nearly the same rate today and in the past produced the various geologic features over an expansive timeline and in a predictable manner.
Using his legal skills in arguing and rhetoric, he came up with a very convincing case to support uniformitarianism. He wanted an intellectual approach to dealing with challenges in interpreting rocks and doing away with using the Bible, supernatural or wild speculations to explain Earth’s history.
His efforts made uniformitarianism, a methodological principle of using the present to infer the past, deeply and widely applied in practicing historical geology by the early 20th century.
Of course, Lyell knew the role of local floods, earthquakes, volcanic eruptions, etc., or catastrophes in shaping the Earth. However, he believed that the uniform, gradual ordinary geological processes that Hutton proposed had a huge cumulative effect over a long time and carried more significance. Thus, he didn’t include catastrophic events in his uniformitarian framework.
He also rejected not only neptunism but also catastrophism. Why? Because he felt no sudden worldwide catastrophe series, including diluvialism, resulted in Earth’s geologic record. To him, it was an attempt to fit Earth’s time scale or chronology to biblical timelines, something grossly inaccurate and couldn’t explain the seen geological features.
Lastly, through his argument and work, Lyell introduced unlimited geologic time and the notion that the whole Earth didn’t change over time, i.e., was constant or at equilibrium over time. For instance, the rates of volcanic eruptions and overall climates remained the same; one change countered the other.
3. Charles Darwin support
Lyell’s work influenced Charles Darwin by applying gradualism or gradual change over time in his theory On the Origin of Species in 1859. He said geologic evidence proved a vast amount of time, and if there was enough time to erode mountains, then there was enough time for millions of organisms to emerge, evolve into new ones, or go extinct.
What is the uniformitarianism doctrine?
The principle of uniformitarianism states natural laws and processes that happen today also happened in the past but not necessarily at the same rate or intensity. Therefore, the modern geological processes we observe are key to understanding and interpreting the ancient geological processes and features.
Put differently, the uniformitarianism doctrine states that physical and chemical processes and forces operating today also operated in the past, i.e., haven’t changed. These forces and processes scientifically observable today are the same that shaped the Earth through history, i.e., create or destroy geological features – rocks, fossils, landforms, etc.
The basis of uniformitarianism is the forces and processes remaining the same and operating throughout the geologic timeline, but rates or durations don’t stay the same. Also, we cannot ignore the role of catastrophes like floods, tsunamis, earthquakes, landslides, and volcanoes, including those of no known analogs.
When we talk about geologic processes (chemical or physical), we refer to weathering, erosion, sediment transportation and deposition, lithification, volcanism, earthquakes, etc.
Geologists, paleontologists, geomorphologists, geoscientists, or Earth scientists often want to claim ownership of the principle of uniformitarianism because geologic observations helped develop it. However, it is a basic principle underlying all scientific inquiries, including biology, archeology, anthropology, Earth science, evolution, and other sciences. You cannot conduct scientific experiments if nature doesn’t act similarly.
Lastly, in their inquiry, geologists use postdiction retrodiction, not prediction. It implies they think backward using geologic data in fossils or rock to help infer possible processes involved and rates resulting in whatever they are measuring or studying. Such a study requires uniformitarianism to justify using such a procedure.
why uniformitarianism is important
Uniformitarianism helps geologists and other people of other sciences since it is the basis of all scientific inquiries as it defines natural laws and processes as invariable or those that don’t change. This assumption helps us conduct scientific experiments and studies.
Also, using modern observable processes, environments, or analogs and applying inductive thinking, uniformitarianism allows geologists to analyze, extrapolate, and interpret preserved past evidence like past rocks, fossils, and ancient geological phenomena and predict possible future.
For instance, fossil assemblage, burial, and preservation can infer zonal paleoclimates and past events such as mass extinctions. Also, geological features on rocks can tell you about their origin or formation.
Modern uniformitarianism or actualism
Is uniformitarianism true? It depends. If the term uniformitarianism indicates the uniformity of rate (steady statism) and of the process, as Lyell thought, it is ambiguous and untrue. Why? It presents two problems or limitations, i.e., 1) rates of processes, intensity, and duration changes and 2) short-lived, sudden events help shape landscape too.
Currently, geologists use actualism to refer to modern uniformitarianism, whose meaning is closer to how Hutton envisioned it. The Earth is 4.543 billion years old, meaning there is enough for catastrophic and slow processes like erosion, sediment transportation, deposition, etc., to sculpt it.
Actualism is the idea that laws or principles of nature remain the same, a central assumption for all sciences. It uses what you can see operating at present to infer an ancient geomorphological phenomenon—no need to invent or search for new processes to explain it.
Therefore, to modern geologists or actualists, uniformitarianism states that 1) natural laws or process operating today also operated in the past and will operate in the future, 2) these laws and process can have different durations and operate in different rates or intensities – scales vary space and time and 3) sudden, short-lived punctuated events including those of no known analogs helped shaped the history of the Earth including crust, climate, and life.
Earth is dynamic, but the process and natural laws remain unchanged. This definition doesn’t invalidate gradual processes like mountain erosion, transport, deposition of sediments, and subsequent land uplift, which take millions of years. However, how can you ignore earthquakes causing faults on the ground and volcanoes adding rock onto eroding mountains?
Some sudden punctuated events or catastrophes include earthquakes, tsunamis, volcanic eruptions, floods, mudslides, drifting continents, etc. These can include events not known to man, like:
- The Archean Eon (4 to 2.5 billion years ago) was without oxygen to support life, including vegetation. Such times must have experienced more erosion with coarse sediments.
- Asteroid impacts like the Cretaceous–Paleogene (66 million years ago) killed nearly 75% of the organisms, including the mass extinction of non-avian dinosaurs.
- The Snowball Earth
- Louis Agassiz’s continental glaciations
- Enormous flood-basalt volcanic eruptions and Siberian Traps formation
- Great oxygenation event
- Sulfur-rich Canfield oceans
References
- Levin, H. L., & King, D. T. (2016). The Earth through time, 11th edition (11th ed.). Wiley.
- Kusky, T. M., & Cullen, K. E. (2005). Encyclopedia of earth and space science. Facts on File.
- MacLeod, N (2005). Stratigraphical Principles. In Selley, R. C., Morrison, C. L. R., & Plimer, I. R. (Eds.). Encyclopedia of geology (Vols. 1-5). Elsevier Academic.
- Wicander, R., & Monroe, J. S. (2010). Historical geology: Evolution of the Earth and life through time (6th ed.). Books-Cole.
- Grotzinger, J. P., & Jordan, T. H. (2014). Understanding earth (7th ed.). W.H. Freeman and Company.
- Levin, H. L., & King, D. T. (2016). The Earth through time, 11th edition (11th ed.). Wiley.
- Prothero, D. R., & Schwab, F. (2014). Sedimentary geology: An introduction to sedimentary rocks and Stratigraphy (3rd ed.). W.H. Freeman and Company.
- Ward, P. D., & Kirschvink, J. L. (2016). A new history of life: The radical new discoveries about the origins and evolution of life on Earth. Bloomsbury.
- Martin, R. E. (2018). Earth’s evolving systems: The history of planet earth (2nd ed.). Jones & Bartlett Learning.