any spatial attributes (especially as defined by outline)
All were strangely shaped, and the Spy-glass, which was by three or four hundred feet the tallest on the island, was likewise the strangest in configuration, running up sheer from almost every side and then suddenly cut off at the top like a pedestal to put a statue on.
I had now come out upon the skirts of an open piece of undulating, sandy country, about a mile long, dotted with a few pines and a great number of contorted trees, not unlike the oak in growth, but pale in the foliage, like willows.
low-lying wet land with grassy vegetation; usually is a transition zone between land and water
The thicket stretched down from the top of one of the sandy knolls, spreading and growing taller as it went, until it reached the margin of the broad, reedy fen, through which the nearest of the little rivers soaked its way into the anchorage.
and long after that death yell was still ringing in my brain, silence had re-established its empire, and only the rustle of the redescending birds and the boom of the distant surges disturbed the languor of the afternoon.
Everything else was unchanged, the sun still shining mercilessly on the steaming marsh and the tall pinnacle of the mountain, and I could scarce persuade myself that murder had been actually done and a human life cruelly cut short a moment since before my eyes.
Additional definitions of "desolate" as an adjective are "reduced in population; deserted" and "crushed by grief"--the first would be fitting descriptions of the island, and the second would be a fitting description of someone who had been marooned on the island. As a verb, "desolate" means "leave someone who needs or counts on you"--this would not be a fitting description of the island, but it could describe the action of angry shipmates.
I had heard the word, and I knew it stood for a horrible kind of punishment common enough among the buccaneers, in which the offender is put ashore with a little powder and shot and left behind on some desolate and distant island.