A sea of mountains stretching out to the horizon on a blue bird October day in the San Juan Mountains. The ragged peaks of the San Juans are the product of eons of violent volcanic eruptions that spewed molten lava and hot ash over elevated terrain that had been thrust up by the collision of two tectonic plates. The volcanic rocks accumulated to many thousands of feet thick over an area of several thousand square miles in what is now southwestern Colorado. After volcanic activity ceased, water began sculpting the range, with mighty glaciers carving broad and steep walled valleys during glacial periods, and rivers and streams incising narrow gorges and steep walled canyons during warmer times. While these mountains may seem immutable to the human observer, they are slowly being worn down, and one day will be wiped clean from the surface of the Earth. How lucky we are to be able to experience them now.