Known locally as the Albuquerque Volcanoes or the Three Sisters, they are a classic and rare example of a fissure eruption. In fissure eruptions magma rises along thin cracks in the Earth’s crust unlike most volcanoes in which magma rises through a vertical central vent. Here the fissure is over 5 miles (8km) long. Very long cracks like these may result in a row of aligned eruption craters—all active at the same time. Such eruptions create “curtains of fire” like those that occur today at Kilauea in Hawaii Volcanoes National Park. The Rio Grande Rift. The volcanoes are located near the middle of the Rio Grande Rift Valley. A rift valley is a zone of weakness and thinning in the Earth’s crust. As the crust is pulled apart, large blocks of land drop down forming the valley. Thin cracks open deep into the Earth releasing molten lava while blocks on one or both sides of the valley rise. The Sandia Mountains, just east of Albuquerque, formed by uplift along a major fault that marks the eastern edge of the valley. The Rio Grande Rift Valley extends from southern Colorado south to El Paso, Texas. It is one of only few active rifts. Others include the East African Rift, the Rhine Graben in Germany, and the Lake Baikal Rift in Russia.