During costume-making madness, I've been listening to a lot of lectures. Might as well improve your mind whilst preparing for Halloween, eh?
One of the lectures I've listened to is Dr. Eugenie Scott's "What Would Darwin Say to Today's Creationists?" One of the things I like about Dr. Scott is that she doesn't just stop at evolution when it comes to fighting religious nonsense pawned off on the public as "science" - she's also aware of Flood geology and takes time to debunk it, too. And she knew Darwin started his career in science as a geologist. Also, if you head to round the 25 minute mark in that video, you'll get an excellent description of what uniformitarianism is - and isn't.
Most of us know the basics of uniformitarianism: processes we see acting today acted in the past, and explain what we see in the geologic record. It includes the concept of gradual change over time (which is one of those things that got Darwin thinking along the path that led him to evolution). But Dr. Scott makes an excellent point that states more clearly than any other source I've heard why Flood geologists and other creationists are so very wrong when they point to events like the eruption of Mount St. Helens and the spectacular erosion seen in its aftermath, and claim this as proof that the Earth's geology was created in catastrophe instead of forming gradually over time:
"Uniformitarianism, by the way, does not mean that everything that happened in geological history is slow and gradual. Lyell and Darwin and the other scientists of the day knew that there were catastrophic events that produced geological changes, but it's the process that is the uniformity, as it were, from one time to another. The rate doesn't have to be the same."
Keep that quote handy. If you spend much time round Mount St. Helens, you'll eventually run into flocks of creationists who love to misunderstand uniformitarianism. Their misunderstanding may be willful - but they'll have a much harder time confusing innocent bystanders if you explain catastrophes (though not worldwide floods) are very much a part of genuine geology.