A Historical Look At Geology

How did we go from scratching at the Earth for historical clues about people to the sophisticated geological laboratories of today? Geology describes the Earth and how it has changed over time, but indeed it took many centuries to reach a point where people had the scientific knowledge to describe how the planet changed over time.

Prior to the Enlightenment

The first observations about the geological world came from Aristotle, who claimed that the Earth changed, but this change was slow to the point of imperceptibility. Over the Greek and Roman periods, scholars would mostly confine themselves to describing the rocks, minerals, and metals they encountered, as in Theophrastus’ On Stones. Xenophanes, at the same time, commented on the presence of marine fossils far from the ocean, but admitted that he could not figure out the mechanism by which they arrived there. The actual processes of geology were generally not studied.

Avicenna continued Aristotle’s program of proto-geological thought after the fall of Rome, in addition to other Islamic scholars.  In China and India, independent schools of geological thought were developing. Chinese polymaths like Shen Kuo and Zhu Xi developed geomorphology and stratigraphy generations before their Western counterparts. Writing on the deposition of strata, the presence of marine fossils far from the ocean, and the appearance of other out-of-place fossils, they assembled a geomorphological research program akin to the one being used today.

The Canadian Museum of Civilization discusses ancient Greek geography.

A description of discoveries made by Medieval Islamic scholars in the field of geology.

An introduction to the works of Shen Kuo.

Enlightenment & Onwards

Before the Enlightenment, the Bible was viewed by the scholars of Europe as the principal source of geological information, an infallible text that could serve to explain all geological phenomena. During that great period of interrogation of what had previously been thought to be impervious truths, people began to question whether the Bible’s account of creation was correct.

A group of geologists who called themselves “plutonists” saw slow geological processes like volcanism as the reason for the existence of rocks in general.  ”Neptunists” saw rocks has having been deposited after the historical Great Flood. The debate was a major part of the intellectual life of France and Britain, and in France in 1741, the first geology courses were taught. In 1749, Georges-Louis Leclerc demonstrated that the Earth was many times older than had been inferred from Biblical interpretation. The Scottish geologist James Hutton came to believe that the same processes that have changed the Earth in the past are changing it today. His theory, called “uniformitarianism,” remains the basis of geological theory.

The 19th Century saw leaps and bounds in geological thought. In 1815, William Smith, a largely self-educated canal-digger and coal miner, used his knowledge of strata to represent strata horizontally as well as vertically by drafting the world’s first geological map. Charles Lyell became the foremost academic geologist of the time, establishing that different strata were associated with different fossil records, and documenting these strata.

Since much of the geology of the time was based on fossils (as it is today), Darwin’s theories of evolution were a major contribution to modern geological thought. Geological diggings provided further evidence for the evolution of organisms, and evolutionary biology gave geology a framework to explain why organisms showed subtle differences between strata. Geology quickly moved from curiosity to major source of funding, from states, academic institutions, and private companies. Searching for natural resources such as oil, coal, and precious metals, these institutions recognized that a thorough knowledge of geology was necessary for exploitation of those resources.

In the 20th Century, geologists moved from talking about the Earth’s history in terms of millions of years to talking about it in terms of billions of years. This suggested not only did organisms and climate change in a given location, but that the continents themselves moved around. This provided the basis for Alfred Wegener’s theory of continental drift. New engineering techniques in the mid-20th Century allowed for deeper examination of the substances below the Earth’s surface. Rather than the continents themselves shifting, large-scale “plates” were discovered, crashing into each other and relocating over the course of millennia. These plates sliding into each other leads to the formation of mountains and volcanoes.

As investigation techniques become more and more complex, geologists acquire new ways of observing the Earth and are able to analyze rocks in different ways. For instance, the development of satellite imagery has allowed geologists to make comparisons between the mountains of disparate parts of the planet. Despite all these new methods, geology is still very much a field-based discipline. So much geology requires the scientist to go out and collect samples. Much as it was 200 years ago, the study requires the geologist to patiently look below their feet and examine the Earth.

Additional Information

The following links are more general introductions to geological concepts and the history of geology.

  • Geology.com is an educational portal hosts tutorials and news updates on earth science.
  • LANDSAT is NASA’s satellite observation program. It is a major part of the modern geologist’s toolbox.
  • A blog with regular updates discussing the history of geology.
  • The Geological Society of America’s History and Philosophy of Geology Section is dedicated to studying the contexts in which geology takes place.

IMAGE: William Smith’s geological map of England, circa 1812 (Source: Wikimedia Commons)