This 375,000 acre parkland is about 20 miles south of Grants, New Mexico. It is an area of lava flows, lava tubes and caves and cinder cones. This area was formed from volcanic eruptions and lava flows that occurred only about 115,000 years ago.
Here is one of the large sink holes that was formed from when a portion of a lava tube collapsed.
And a portion of the trail in El Malpais.