I really chewed up my original comment. "a mudslide or a storm" was supposed to bind to the bit about organic fossils, not the bit about inorganic artifacts. I

I really chewed up my original comment. "a mudslide or a storm" was supposed to bind to the bit about organic fossils, not the bit about inorganic artifacts. I think "rapid" might be a relative term (I'm thinking of the Mary Rose and the Vasa). When you get to the more durable artifacts that come with a technological civilization we really should be thinking in decades, maybe centuries.