The Rocky Mountains, reaching altitudes of more than 13,000 feet, are well watered and forested and support recreational activities including skiing, fishing, hunting, and camping. To the north are numerous volcanic peaks lying east of the Rocky Mountains in both Colorado and New Mexico. The elevation here is 6,300 feet. The treeless grasslands of the High Plains cover the eastern one third of New Mexico and stretch eastward into the mid-continent. Surface water from the mountains, together with underground aquifers, permits ranching as the principal economic activity. Carbon dioxide gas, a geologic resource, has been discovered and developed in the subsurface.