"Alf P. Steinbach" wrote in message
...

Please note, English is not my native language.

I understand. I will try to be clear.

"Alf P. Steinbach" wrote in message
...

But exactly what is a "mesa" that sticks up above the
surroundings?

The word " mesa" , which means " table " in Spanish, is
defined (in a geological context) as an isolated, relatively
flat-topped natural elevation - usually more extensive than
a "butte" and less extensive than a "plateau".

Google and Hyperdictionary insists a mesa is a depression,
a basin.

I don't know what to say about that except that I've never seen
the word "mesa" used in any context to refer to a depression.
For what it's worth, I live on a mesa. I drive uphill to go home
and downhill to leave.

And these particular mesas, if that's what they are, seem to be
incredibly smooth on top, and have very strange droplet-like
boundaries.

Mars Global Surveyor imagery has revealed that there are a
great many extremely flat mesas on Mars. The shadowy
appearence around the rims could be caused by several things
(such as wind-induced dust build-up or removal; uneven sublimation
of ices or frosts, etc.) and does not necessarily represent a
curvature of the edge. The image is indeed filled with optical
illusions.

So (C) is a kind of rectangular kilometerwide "mesa" that like (A) sticks
up above the surroundings, but unlike (A) has ordinary-looking boundaries
and a sort of corrugated interior instead of (A)'s very smooth interior?

Your description looks about right.