Sunset Crater Volcano National Monument

Sunset Crater Arizona: Birth of a Mountain

Erupting sometime between 1040 and 1100 Sunset Crater is the most recent volcanic activity in the Flagstaff area. This cinder cone reminds us of the powerful forces that shape the Earth – forces that have created more than 600 hills and mountains in the San Francisco volcanic field. These mountains have in turn affected the climate and habitat for all things living in this region.

What is now a 1,000-foot-high volcano began to form when molten rock sprayed high into the air from a crack in the ground, solidified, then fell to Earth as large bombs or smaller cinders. As periodic eruptions continued, the heavier debris accumulated around the vent. The lightest, smallest particles were carried the farthest by wind, dusting 800 square miles of northern Arizona with ash. Perhaps as spectacular as the original eruption were two lava flows: the Kana-a and the Bonita. They destroyed all living things in their path.

Lava Flow

The processes that created Sunset Crater also created a sculpture garden of extraordinary lava flow forms at its base. As new gas vents opened, spatter cones sprouted from the ground – like miniatures of the volcano itself. Partially cooled lava, pushing through cracks in the crust like toothpaste from a tube, solidified into wedge-shaped squeeze-ups, grooved from scraping against harder rock.

The entire event may have lasted six months to a year. In a final burst of activity red and yellow oxidized cinders shot out of the vent and fell onto the rim. The colorful glow from these cinders reminded people of a sunset and led to the volcano’s name.

Formation of Cinder Cone Volcanoes

Cinder cones volcanoes, such as Sunset Crater, are formed during early explosive stages of an eruption. Magma, a mixture of molten rock and highly compressed gases, rises upward from its underground source. As the magma ascends, the extreme pressure drops and gases are released. The high percentage of gas in the magma causes an explosion out of the central vent. Solidified rock pieces of various sizes fall around the vent, creating a mound or cone. Magma with a lower gas content produces lava flows that may issue from the side or base of the cone.

Exploring Wupatki and Sunset Crater Volcano

The landscape that shaped the lives of people 800 years ago appears unchanged in many ways since the eruptions. The lava flow near Sunset Crater seem to have hardened to a rough surface only yesterday. From a distance the pueblos at Wupatki National Monument look as though they could still be occupied. But many processes have been at work, reshaping the land into what we see today.

Vandalism, tectonics, and erosion have created dramatic geological formations and abrupt changes in elevation and climate. As you travel the loop road between Sunset Crater Volcano and Wupatki national monuments, the environments range from desert to mountain. Ecosystem changes are distinct and frequent. These changes within a relatively short distance greatly increase the biological diversity of the area -– a diversity that was indispensable to early residents.

Residents, in turn, transformed the land as they harvested the wood for homes and fuel, hunted and gathered wild foods, and introduced cultivated crops. Later, Navajo families settled the Wupatki area and brought sheep to the land. Beginning in the 19^th century, newcomers introduced cattle, tapped ground water supplies and interrupted the natural processed of wildfire. As a result, juniper trees have invaded grasslands; ponderosa forest are no longer open and spacious but dense with undergrowth; some seeps and springs no longer flow.

These habitat changes have affected some species and created new niches for others. In the higher elevations among the ponderosa pine, Albert’s squirrels and vivid blue Steller jays are common. Middle elevations support pinyon pine, one-seed juniper, and grasslands, along with jackrabbits and pronghorn antelope. In the lower lands, the more sparsely vegetated high desert community is home to lizards, snakes, coyotes, and bobcats.

As part of the US National Parks, Wupatki and Sunset Crater Volcano national monuments are managed to perpetuate this geologic landscape that preserves increasingly rare habitat for native plants and animals and to protect past human developments and their relationships to the land.