So Google has this thing called "Google Trends" and it tracks the instance of words put into its search engine and where most of the search requests come from...
So naturally, I put in "caving" and got this:
http://tinyurl.com/oa9no
Denver seems to be the city that has searched caving more than any other in the United States. And what was the spike in "news volume" of caving stories in the spring of 2004 (March)?
If you search "caves" then it changes and Austin is the city that searched the most for "caves" (Denver drops to #10). Also the news spike is in April of 2004 when this story came out:
3 Teens Die Exploring Minn. Caves
Wilkes Barre Times-Leader - Apr 28 2004
http://tinyurl.com/mm7x7