Before Darwin was famous, another revolutionary voice rang out over the western world. Charles Lyell, lawyer and geology buff, was one of the early voices to speak out against the eyewitness testimony of the biblical writers.
James Hutton had done “pioneering work in geology” toward the end of the 18th Century, opening the door to using the rock record as an authority rather than written records. Charles Lyell followed in his footsteps, writing a three-volume treatise in 1831–33, titled:
Principles of Geology: Being an Attempt to Explain the Former Changes of the Earth’s Surface, by Reference to Causes Now in Operation
As you can see, he had already precluded any catastrophic event such as the global flood a priori. As Wikipedia says:
The central argument in Principles was that “the present is the key to the past”: that geological remains from the distant past could, and should, be explained by reference to geological processes now in operation and thus directly observable.
But it wasn’t enough for him to look at his local rocks in Scotland and extrapolate backward in time. Lyell traveled widely looking for rock processes to apply his principle of “Uniformitarianism” to.
Niagara Falls
A decade after publishing his books, Lyell visited this famous landmark. In 1841 it was hardly the honeymoon destination it would later become. It wasn’t easy to get to and few English-speaking people had seen it with their own eyes.
There were, however, locals—including the son of a geologist—who reported that the Niagara River was eroding its gorge at a rate of at least a meter [3 feet, 3 inches] per year. Calculating the distance from the mouth of the river to the location of the falls at the time only worked out to a maximum of <12,000 years.
In fact, later observations into the 1920s, before the diversion of a large portion of the water, gave an average recession rate of nearly six feet per year, making the uniformitarian maximum age even younger.
But did this convince Lyell?
When he returned to England, Lyell released an updated version of his Principles of Geology in which he reported that Niagara Falls had taken 35,000 years to erode to its present location. He never explained why he discarded the observed erosional rates or how he arrived at his revised estimate of <1 foot [0.3 meters] of erosion a year.
Lyell was well respected. He could explain the process of erosion quite well.
People trusted him.
Clergymen trusted him.
If Lyell’s Dates were Right, the Bible had to be Reinterpreted
And that’s what many did.
Darwin took an early copy of Lyell’s book with him on his transformative trip aboard the HMS Beagle.
To have evolution work, you must have long ages. Lyell made it possible to find all kinds of time in the rocks. Anything sounds believable when it happened long ago and far away.
I am sure you may get into Q. R. [Quarterly Review] what will free the science from Moses … . I conceived the idea five or six years ago, that if ever the Mosaic geology could be set down [i.e. repudiated—Ed.] without giving offence, it would be in an historical sketch, and you must abstract mine … ~Charles Lyell in a letter to George Poulett Scrope, June 14, 1830
Sources
Answers in Genesis: Niagara Falls and the Bible
Creation Ministries International: Charles Lyell
https://answersingenesis.org/geology/natural-features/niagara-falls-and-the-bible/