The largely Miocene-to-Pliocene island of Gran Canaria in the middle of the Canary archipelago has been strongly eroded into steep-walled radial gorges called barrancos.  Three major volcanic structures form the circular 60-km-wide island, which has been modified by caldera collapse, gravitational edifice failure, and extensive erosion.  Middle Quaternary scoria cones and lava flows are found in the northern and eastern parts of the massive shield volcano, which is cut by a major NW-SE-trending rift zone that extends across the island and fed flows primarily to the NE.  Very young basaltic cones and lava flows of Holocene age are situated within a NW-trending zone from Berrazales to Bandama and at Las Isletas, a peninsula on the NE coast.  One cinder cone was radiocarbon dated at about 3000 years before present, and other cones and flows may be less than 1000 years old.