The Heart of Mordor   I made a solo hike out to the edge of a volcano. On a dark and moonless night, you could see the billowing yellow smoke - toxic sulfur dioxide - from miles away. After walking over the rough terrain of volcanic rock, I came to the rim and set eyes upon what lay within the caldera - a roiling lava lake that moved in waves and cackled like shattering glass as the ever-expanding rim eroded into it.