[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?