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Summary: We went to Sunset Crater National Monument.

Monday, Sept 14th: We left Parker early to try and "beat the heat". We went north on Hwy 95 to Lake Havasu City. We took Hwy 40 through Kingman to Flagstaff. We then turned off of Hwy 40 to Hwy 89. About 12 miles north of Flagstaff, we turned off Hwy 89 onto a loop road that took us through Sunset Crater National Monument (250 miles).

On the way to our favorite campsite, just outside the Sunset Crater National Monument, we stopped at the Lava Flow Trail. We walked the easy 1/4-mile paved trail at the base of Sunset Crater. There is a longer 1-mile trail down into the lava flow, but we've done that before.

About 1,000 years ago, something spectacular happened in the lives of local Native peoples. A 1,000-foot-high cinder cone, known today as Sunset Crater, grew where open parks and forests had been. Volcanic ash buried about 64,000 acres of potential farmland. Many people lost their homes and livelihoods. Stories symbolizing the significance of the eruption were told and retold.

As we crossed the bridge there was a very obvious white spot in the black lava. This is a xenolith (zee-no-lith), a rock fragment foreign to the body of rock in which it occurs. When magma rose to the surface, it brought up pieces of limestone from 700 to 1,000 feet below the surface. Uplift and erosion have exposed this rock (known as Kaibab limestone) elsewhere: at the rims of Grand Canyon, nearby Walnut Canyon and in cliffs at Wupatki National Monument.

As lava flowed from the base of Sunset Crater volcano, it cooled and hardened into many fascinating patterns and shapes, leaving behind a bizarre landscape frozen in time. Squeeze-ups form when molten lava oozes out through a crack in a solid lava shell. The pressed-up lava is very plastic, like clay, and is molded into a wedge-shaped mass as it rises from the crack. As the squeeze-up grows, gravity causes it to bend from its weight.

Lava oozed off and on many times creating a very structurally complex flow, covering about 2 square miles. Lava flows tend to form either jagged blocks, known as aa (ah-ah), or a smooth, ropey surface of pahoehoe (pa-hoy-hoy). Flows usually start as pahoehoe, thin and runny. As the lava cools and becomes more thick and pasty, it can change into an aa flow. The Bonito Flow is mostly aa lava. We saw these two kinds of lava flow very clearly when we were in the Galapagos Islands in April, 2009. We've read this brochure before, but didn't remember about the aa and pahoehoe type lava flow.

Lichens, in a myriad of forms and colors, are the rsult of a symbiotic association between algae and fungi. They live a very long time. These on the rocks, whether soft green, neon yellow, or orange, may have begun forming not long after the lava cooled. Lichens are very sensitive to air pollution; their health can provide early warning of changing conditions.

006-Lava Flow Trail view, Sunset Crater.JPG

007-Xenolith rock at Sunset Crater.JPG

009-Squeeze-up, Sunset Crater.JPG

010-Aa lava flow with lichen, Sunset Crater.jpg
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