Sunset Crater: Lava and more lava!
Established as a National Park in 1930, the Sunset Crater cinder-cone resulted from an eruption that took place about 900 years ago. They have have not found any indication that people perished during the eruption — the general theory is that there were a lot of warning signs before the volcano erupted and everyone beat feet.
There are a lot of dead trees in the park, in addition to live ones!
The lava flows on display are frozen in place, like it just happened a few years ago. The lava fields go on forever — it's amazing! There are a few trail options that take you right through the lava fields and are worth exploring.
Bonito Lava Flow. The Sunset Crater is in the background.
An aspen tree, making it's way in a tough environment.
Overall, though, hiking is limited due to the ecological sensitivity and damaged inflicted by early tourists. As of 1970, you can no longer hike up the crater, but you can hike up Lenox crater which is close by, and erupted prior to the Sunset crater. In fact, the ash and cinder from Sunset filled in the "crater" of the Lenox crater.
View from on top of Lenox Crater. Almost 1,000 years later...the area is still nothing like the meadow it was prior to the eruption.
If you aren't in the mood for hiking, you can enjoy the 35-mile driving loop that also takes you to Wupatki National monument, where you can see pueblo ruins dating back to about 800 years ago. If you are in the area, it's totally worth a visit. And why not...it's even right on the way to the Grand Canyon!