Here's a breakdown:

* Catastrophism: This theory suggests that Earth's geological features were formed by sudden, violent events, such as catastrophic floods, volcanic eruptions, and meteor impacts. It was a dominant view in the 17th and 18th centuries, influenced by religious interpretations of the Bible.

* Uniformitarianism: This theory, proposed by James Hutton and popularized by Charles Lyell, argues that geological processes occurring today are the same as those that have occurred in the past, and that these processes happen gradually over long periods. It is the prevailing view in modern geology.

Key Differences:

* Time Scale: Catastrophism emphasizes rapid, dramatic changes, while uniformitarianism emphasizes slow, gradual changes over immense periods.

* Explanation: Catastrophism explains geological features as the result of sudden, catastrophic events, while uniformitarianism attributes them to ongoing, natural processes.

While catastrophism has been largely discredited, it's important to acknowledge that:

* Some events are indeed catastrophic: While most geological processes are gradual, some events like meteor impacts and supervolcanic eruptions can cause dramatic, sudden changes.

* Catastrophism can be a useful concept: It helps us understand the potential for rapid change and its impact on Earth's history.

Therefore, the idea of geologic change happening suddenly is an older, largely outdated theory, but it still provides valuable insight into the dynamic nature of our planet.