Happy Darwin Day
Of course today has been designated "Darwin Day". While Darwin's "dangerous idea" had a profound impact on biology, it has also affected the geological sciences in a poignant way. At the time Darwin wrote his book, the age of the earth was being worked out by prominent scientists such as Joly and Kelvin. Darwin's idea made a specific prediction about the age of the earth--- namely that it had to be quite old if the diversity of life such as he knew it formed from the first organisms to emerge from that 'warm little pond'. While Kelvin's calculations held sway within the geologic community for some time in the late 1800's, Darwin's estimate for a much older earth was vindicated through the discovery of radioactive decay. It was not until ~100 years following the "origin of the Species" initial publication that the current age of the Earth was worked out to be ~4.5 billion years (for a nice read about the efforts of Arthur Holmes and colleagues to come up with this age, I suggest Cherry Lewis' book "The Dating Game".
The fossil record was tagged by Darwin for its importance in solving the history of life on earth and offers a wonderful confirmation of his theory of natural selection and biological change. Darwin also made contributions to geology such as the formation of atolls.
Darwin's ideas about how species vary from place to place was instrumental in providing evidence for continental drift. Work on the fossil record provided extraordinary evidence for faunal provinciality and for the motions of the continents.
Darwin can also be credited (at least partially) for the involvement of geology in solving 'problems' such as the Cambrian explosion (Darwins dilemma). His notion of life forming in a 'warm little pond' has driven many geobiologists and geologists to spend time on ancient outcrops looking for the oldest forms of life and thinking about the chemistry and environment that resulted in the very first replicators.
My own research on the motion of continents through time touches on Darwins dilemma because we can provide the paleogeographic setting for the expansion of Cambrian lifeforms and help to establish the timeline and tempo of evolutionary events.
Darwin's work has influenced a great deal of scientific thought and I think it's entirely appropos that we celebrate those contributions.