Early scientists sought to explain the physical world around them.
Many of these early scientists were naturalists, who examined the physical world and sought to explain what they observed.

One such naturalist was the French zoologist, Georges Cuvier. Cuvier lived from 1769 to 1832. Cuvier suggested that the biological and physical features on Earth’s surface today can be explained by the concept of catastrophism.

Catastrophism is the idea that a series of sudden and widespread catastrophes created the features on Earth.

The catastrophes that Cuvier referred to would have caused rapid and significant changes on Earth.

Cuvier suggested that six major catastrophes have occurred throughout Earth’s history. Each catastrophe, which could have been a major flood, volcanic eruption, or earthquake, caused life in the area to die off. He suggested that after each catastrophe, new organisms either were created or moved from other areas.

Cuvier’s six major catastrophic correspond to the six days of creation found in the Bible. He also listed the last of the six catastrophes as the biblical flood. His ideas supported the idea that Earth was very young – about 6,000 years old.

The idea of catastrophism was not a valid hypothesis.
There was no real evidence in the rocks that supported the hypothesis of six major catastrophies in Earth’s history.

The concept of catastrophism continued to dominate scientific thinking until the 1800s. In 1830 Charles Lyell published a book called Principles of Geology. In this book he discussed the ideas of James Hutton. These ideas Lyell called uniformitarianism.

Many of the ideas were Hutton’s, but Lyell was really the one to give the ideas a voice. Hutton was not as successful as a writer, and Lyell was able to get his ideas out to a broader audience.

Hutton, and also Lyell, saw the history of Earth as being cyclical in nature. They noted that continents eroded, these eroded sediments were deposited in oceans, and later the ocean floor was uplifted to create new continents. This was a large cycle.

Hutton’s observations and data suggested that the source of energy for this uplift came from the hot interior of Earth.

He had originally thought that igneous rocks formed through a process called plutonism. Plutonism was the idea that igneous rocks came from cooling magmas. This replaced what was at the time the prevalent idea for the origin of igneous rocks. That was a theory called neptunism which said that igneous rocks dropped out of solution from sea water.

Hutton also expressed the significance of unconformities. An unconformity is a gap in time, indicating time of erosion n the rock record. He studied rocks in Scotland and found rocks that were tilted upward overlaid by horizontal layers. This indicated, to him, that the gap in time between the tilting and the horizontal deposition was significant.

Hutton also was one of the first to suggest that geological processes take a very long time.

When Charles Lyell looked at Hutton’s work he recognized that small changes today that result from geological processes could have a huge impact on Earth’s surface over long periods of time.

Lyell is largely credited with disproving catastrophism as an explanation for geologic phenomena.

Fun fact: Some scientists prefer the term “actualism” today. They prefer actualism to uniformitarianism because it gets rid of the idea that geologic processes are “uniform.”