What was Charles Lyell main idea?

Charles Lyell's main idea was that geological features are the result of slow and gradual changes over long periods of time, rather than by sudden, catastrophic events. This principle, known as uniformitarianism, challenged the prevailing catastrophism theory, which held that geological features were formed by sudden, violent upheavals. Lyell's work had a profound impact on the field of geology and helped to shape the modern understanding of Earth's history.