Liquid water? What liquid? There is some liquid present, but it's not really the defining characteristic. And yes, it's water.
Deep-sea volcanic vents? No
*yawns* *some applause* An apt description (of both game and answer)

[Irouléguy] I'm usually pretty hopeless at these geographical minerally ones so I leave them to more worthy participants, which I guess doesn't help much. Trouble is, if these posers are not guessed within 3 days, the game tends to lose its momentum. It is now Day 8 of this one so perhaps a chairman's summary of the positives might help? Then a clue?

Chalky] Fair points all, though I have been trying to steer people away from the more detailed minerally answers (and I was away for most of three days). It's really not obscure - I feel sure that everyone will have heard of it.

Summary - it's terrestial, partly solid, sort of an object. (Those are the answers which I think have caused people to go astray, but it's problematic because of what exactly "it" is. Let's say that "the answer" is defined by solid objects.
There's a strong connection to the earth's crust (which is just the top bit of the earth itself -between 5 and 65km thick), and specific geographical features have got strong applause. It's NOT - man-made, either of the Poles, Antarctica, a tectonic plate, an oilfield, a continental shelf, a volcano, the Canadian archipelago, the Greenland icecap (or any other form of ice).
Clues 1) It's very aptly named; 2) it has a university named after it; 3) over four million people went there last year.

Iceland? No
Is it specifically in either the north or southern hemisphere? Yes, the northern.

Metaphorical name? No, if anything the reverse
Northern Europe? No
Is the suffix or word "land" part of its name/identity? *cheering, the audience all put their hands to their ears as through participating in charades* No

North America? *the orchestra strikes up "My country, 'tis of thee" as the audience jump up and down in anticipation* YES!

*exhausted, the audiience can do nothing but sigh in pleasure* We have a winner - it is THE GRAND CANYON! Purely mineral? Not sure about irach's argument, but I'll think about it.
Anyway, the baton finally gets passed on - take it away, irach!

Here goes. Well, its MINERAL once again.

[irach] hmmmm - hope it's snappier than the last one :-)
[Iroulé] GCanyon - classification, perhaps Mineral with Vegetable [and possibly Animal] connections?

I have never seen a more self-indulgent and comprehensively misleading set of comments as in the last AVMA. The Grand Canyon has no more to do with the earth's crust than has the Vale of Evesham. It's a surface feature FFS. So why did the audience wet themselves, generally an indication that one has very nearly hit the bull?

Sorry.. [Inkspot] Not man made.

Call me pedantic, but I would argue that the Grand Canyon is composed entirely of air.

Chalky] Possibly - but then you'd have to apply that to practically every place or geological formation. Would that definition help you to get Everest, for instance?

Rosie] I may have misunderstood what I Googled - I'm no scientist. But this is from the GC National Park's website: The Canyon’s mile-high walls display a largely undisturbed cross section of the Earth’s crust extending back some two billion years.
from http://www.nps.gov/grca/pphtml/subnaturalfeatures14.html
and lots of sites talk about the GC being made by upheavals in the earth's crust, so that was the basis of my reaction. I'm sorry if it was misleading, and you're right about the self-indulgent bit - sorry again.

Kim] Well, that was why I was unsure about the answers to "solid" and "object". But it can't be all air - what about the floor or the sides of the canyon?

move] Is there just one of it?

[Kim} No. Not a geographical feature. [Irouleguy] There are more than one of these.

(Irouléguy) Talk of the earth's crust made me think the answer was something to do with the material of the earth well below the surface whereas the Grand Canyon (and Cheddar Gorge) were gouged out by running water, i.e. surface erosion. Not to worry. :-)

[Rosie] No.

[Irouléguy] Yes!

[Chalky] Not metallic per se, though there may sometimes be metal salts or ions embedded within it.

Chalky] OK2