Sunset Crater Q&A: Facts About Arizona’s Youngest Volcano

5 minute read
by Jake Case

Sunset Crater Forest Featured

What type of volcano is Sunset Crater?

Sunset Crater is a cinder cone volcano. Among the smallest of the volcanoes, a cinder cone erupts gently, spewing small globs of lava that cool into volcanic pebbles called cinders.

Over the course of the eruption, cinders pile into a steep-sided cone, forming a deep crater around the volcano’s vent. Cinder cones are also known as scoria cones.

What type of rock is it made of?

Basalt. A common lava rock, basalt is high in iron, and thus takes on a dark color. The cinders of the volcano itself, as well as its surrounding lava flows, are all made of gray, black, or red basalt.

Why are some of the cinders red?

Oxidation! The rocks contain iron, and the iron rusts (turns red!) when exposed to the elements, just like when you leave a car out in a yard for forty or fifty years. Instead of “rusting”, scientists call this oxidation, which is a chemical reaction between iron and oxygen that results in iron oxide, or rust.

sunset crater red cinders
(Photo Credit: Jake Case)

How old is Sunset Crater?

A little over 900 years old. This may sound old, but in geology, this is really young! Considering the Earth is about 4.6 billion years old, a 900-year-old volcano is just a baby.

According to the latest research, the eruption began sometime between 1085 and 1090 A.D., and lasted no more than two years. Scientists determined these dates using a combination of tree-ring dating, dendrochemistry, paleomagnetic analysis, and archaeological evidence.

Prior to 2011, geologists thought the eruption began in 1064 A.D. and lasted as long as 200 years.

Was the eruption violent?

Not really. Violent eruptions usually happen in silica-rich lavas.

Silica makes the lava thick, causing a buildup of pressure. When the pressure becomes too much, a violent explosion results.

Sunset Crater produced basaltic lava low in silica, and resulted in a relatively calm and “fluid” eruption, much like our present-day volcanoes on the Hawaiian Islands.

However, the eruption did have enough power to spray cinders and volcanic ash dozens of miles across the neighboring landscape.

Were people affected by the eruption?

Yes. A people referred to by archaeologists as the Sinagua lived on the volcanic landscape surrounding Sunset Crater at the time of its eruption.

The Sinaguan homes — many of them partially underground structures called pithouses — were filled with cinders or in some cases burned. The Sinagua abandoned their nearby fields as thick layers of cinders made the farmland unusable.

While there is no archaeological evidence of human deaths associated with the eruption, obviously it uprooted many lives. However, these displaced people thrived following the eruption by relocating to areas when lighter accumulations of ash and cinders provided a boost in fertility to the farmlands. These post-eruption Sinaguan settlements are now preserved as Walnut Canyon National Monument and Wupatki National Monument.

wupatki sunset crater national monument
(Photo Credit: Jake Case)

Is Sunset Crater active (will it erupt again)?

No. Sunset Crater is extinct and will not erupt again. However, there is still an active magma chamber(underground pool of molten rock) under the area, which will undoubtedly produce more eruptions in the future. These eruptions will produce brand new cinder cone volcanoes, some of which might even form right next to Sunset Crater.

Geologists estimate a new eruption happens in the area about once every 1000 years, and since Sunset Crater erupted just under 1000 years ago, we are due for a new volcano to form sometime in next couple hundred years.

So while Sunset Crater itself will not erupt again, there could be an eruption in the direct vicinity in the near future!

How did Sunset Crater get its name?

According to the National Park Service, “Legend has it that (John Wesley) Powell named Sunset Crater for the red and yellow colors of its rim.”

How tall is it?

Sunset Crater rises about 1,000 feet above the surrounding terrain. The summit is at an elevation of 8,042 feet (2,451 meters).

sunset crater cinder cone
(Photo Credit: Jake Case)

Can I climb Sunset Crater?

In theory, yes, but it is illegal! Once upon a time, the National Park Service carved a trail up to the mountain’s summit. However, NPS closed the trail in 1973 because of intensified erosion of the volcano’s loose cinders.

To preserve the fragile hillside from falling apart, hiking on the mountain’s slopes is illegal and considered a federal trespassing violation, punishable by fines and up to six months in prison.

Can I go hiking at Sunset Crater otherwise?

Absolutely — numerous hiking trails traverse the rugged landscape of Sunset Crater Volcano National Monument.

The Lava Flow Trail is a 1-mile interpretive loop with trail markers and a pamphlet available to complete a self-guided tour. Ranger-guided tours are sometimes offered here too, and a .25 mile mini-loop is paved for handicapped access.

For those interested in climbing a cinder cone, the Lenox Crater Trail provides a moderately strenuous hike up to a nice view of the nearby San Francisco Peaks at the summit.

The park includes a few other cool hikes too. Check out this park’s trails page for the full rundown.

sunset crater rainbow
(Photo Credit: Jake Case)

Are there any unique plants at Sunset Crater?

Yes! The Sunset Crater Beardtongue (Penstemon clutei) makes its home here. This small perennial plant only grows in the forests in and around Sunset Crater Volcano National Monument. It’s tubular pink flowers bloom in the spring and summer.

What’s the difference between Sunset Crater and Meteor Crater?

Sunset Crater is an extinct volcano, while Meteor Crater is a meteorite impact site 40 miles southeast of Sunset Crater.

The one-mile wide, 550 foot-deep crater is about 50,000 years old (once again, young by geologic standards) and is the best-preserved meteorite impact site on Earth. Meteor Crater is a spectacular and fascinating place and is well worth a visit for anyone passing through the area.

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