Okay... in honour of the downright strange number of dimes I found today,
this edition of Twenty Questions with a Coin will be played with a shiny 2003 Canadian dime!

(Heads) Hi, everybody!

Let's get things started.
1. Is it animal?

(Tails) No.
2. Vegetable?

(Tails) No.

Hmm... mineral, then.
3. Is it manmade?

(Tails) No.

A natural mineral structure....
4. Is it bigger than my house?

(Tails) No.

5. Is it bigger than a breadbox?

(Heads) Yes.

Between the size of a house and a breadbox, natural mineral structure...
6. Are we talking about a particular mineral or minerals?

(Tails) No.

7. Is it terrestrial?

(Heads) Yes.

8. Is it something formed by water?

(Heads) Yes.

9. Is it a stalagmite or stalactite?

(Tails) No.

Ooh, this is going to be tough. I don't know as much as I should about geology...
Well, water can either erode or deposit.
10. Is this structure caused chiefly by erosion?

(Heads) Yes.

11. Could I pick it up out of the surrounding earth without breaking anything?

(Tails) No.

12. Is it a part of an outdoor landscape, ie., a river delta or sandbar?

(Tails) No.

This is really hard, dude.
13. Is this a hole, valley, gulley, or depression of some kind;
that is to say, is it chiefly categorized by a lack of material?

(Heads) Yes.

14. Is water (which would count as mineral) currently in the picture?

(Heads) Now you're getting it!

Ah, I was focusing too much on rocks.
15. Is the water moving rapidly?

(Tails) No.

16. Ooh! Ooh! A small, subterranean lake! The kind with blind cave fish!

(Heads) Hallelujah!

Hallelujah indeed.
17. Anything else I need to know?

(Tails) You're good to go, chief!

Whew! Didn't think I was going to get it, there. Nice pick, dime!
(Tails) Aw, it's nothing special. Remember, it's not like I have any sort of conscious intent.

Well, that may be true, but it's still a nice thing to attempt to draw.

(Heads) You're welcome. Glad to be of service.