What limits did Charles Lyell place on the frequency and intensity of past volcanic eruptions and earthquakes?

Charles Lyell, a prominent Scottish geologist, advocated for a strict interpretation of uniformitarianism that limited the frequency and intensity of past geologic events.1

Contrary to the "catastrophist" school of thought, which suggested that Earth's history was shaped by occasional, violent phenomena, Lyell argued that past geologic events—such as volcanic eruptions and earthquakes—did not occur more frequently or with greater intensity than they do in the present day. He maintained that the Earth's surface features were altered very gradually through a series of small, consistent changes driven by the same natural processes observed today.12

By asserting that these natural causes have always operated at the same average levels of energy, Lyell promoted a "steady-state" theory of the Earth. This approach required that all past events be explained by processes that behave in the same manner as modern ones, leaving no room for past conditions that lack contemporary counterparts. Through this methodology, Lyell demonstrated that even significant features, such as Mount Etna, were the result of repeated small eruptions rather than cataclysmic upheavals.213