mesa

A flat-topped, steep-sided hill or mountain — wider than it is tall, its summit a remnant of a once-continuous layer of hard rock (often sandstone or basite lava) that has resisted the erosion consuming the softer material around it. Mesas are the desert's monuments, standing above the plains like tables set for no one. As erosion continues, a mesa narrows into a butte; a butte narrows into a pinnacle; and a pinnacle eventually falls.