Newberry National Volcanic Monument

The gray circle on this map represents the rim of the crater, or caldera, of the Newberry Volcano.  Within the rim are two big lakes, Paulina and East, plus several areas of obsidian flows, or places where lava flowed out and hardened to form shiny black rock.  The Big Obsidian Flow (see post above) covers more than 700 acres and is shown as the lowest gray area at the bottom of the caldera so that gives you an idea how big the entire crater is.