Everything has changed in just a decade. It used to be that when you needed to learn something, the best place to go was the library. A librarian would point you to the right book, depending on your age, how smart you appeared to be, and how much detail you needed.
Then along came the Internet, and by that I mean the old Internet, from before the 1980s up to about 1995.
Asking on the Old Internet
Compared to the library, Internet resources were primitive—and they didn't overlap, either. The old Internet was heavily populated by universities, research agencies, and high-tech companies, and it was mainly full of technical data. For personal communication we used e-mail, listservs, and Usenet, along with bulletin-board services (BBSs) and online communities like the Well and Delphi and CompuServe. Chat was there too, in the form of IRC channels. (If you have just a smattering of Unix, most of that old Internet is still there and thriving.)
It was like the real old days, before public libraries. Centuries ago, if you had a question you'd ask the nearest smart person, who'd either answer you or ask someone smarter. Online in the 1980s and early 1990s, you'd ask somebody you knew via e-mail or you'd ask your listserv group, or you'd go to a Usenet newsgroup and, in effect, ask anybody. Answers would come from all kinds of people, and you learned a lot—not just about the subject, but about how to evaluate so-called experts and their answers and their arguments. And you learned something more precious than answers: you learned that you too were an expert about something, even if it was a small or specialized or trivial thing. The old Internet was an exciting, life-changing experience for many people, like taking your mind to a gym.
Asking on the Web
Then along came the World Wide Web, invented in 1990 as a better way to share files between large scientific agencies on the Internet. Now the whole world is there. Today's Web is a mix of the old Internet and the rest of society. The big institutions are there, like news networks, government institutions, schools, corporations, and so on. At the same time there are millions of personal sites and small circles of passionate experts on an unimaginable number of subjects.
Thousands of ask-an-expert sites are out there, and I have put together a list of the ones I've found that specialize in geoscience. What are they good for? Good question.
Many ask-an-expert Web sites are rooted in the old Internet experience. Not only is it fun to get answers to your question, but it's really fun when someone asks you the right question. I get a lot of questions, and believe me, a good question, one you never thought to ask yourself, will push you to learn something new. In fact, good questions are essential to scientific progress. I believe that's one reason many scientific groups create this kind of site.
Usenet groups, on the old Internet, learned to compile lists of frequently asked questions (FAQ files) to save work for everyone, expert and newbie alike. Most of today's Web expert sites do the same. If you ask me, FAQs are the most valuable parts of these sites. The reason is that the Web serves the general public, and the public generally has simple, basic questions about scientific matters. It's easier for everybody if the answers to these questions are in a FAQ.
Are Ask-a-Geologist Sites Best?
Ask-a-geologist sites seem like a good thing. But the experience isn't fast. Many sites warn you to expect a wait of a week or more. The experience is more like writing a letter to someone. Commercial services are faster, and if you're willing to pay a little bit, you can get a high-value response to a sophisticated question. And Wikipedia is always a good starting place for most geological topics if you have a college education.
To ask a question is one thing, but to have a conversation is the ideal. For that, the old Internet forms are better. Web-friendly online forums (like the one I host on this site) are today's version of BBSs. If you're not a beginner in your field of interest, listserv groups—e-mail circles—are a longstanding institution for thoughtful exchanges. Usenet is still going strong, too, including the venerable newsgroup sci.geo.geology. You'll really learn about arguments, good and bad, on Usenet.
And never forget the good old library. If nothing else, you can get Web access there.
PS: This article resulted from an e-mail question: the writer had found an "Ask A Geologist" site once but couldn't locate it again. I knew offhand of at least two, but I quickly found five with that name, plus a couple dozen more. Jeffrey, this is a long answer, but thanks for your question.