El Malpais is loaded with a group of volcanos that create cinder cones and really cool caves that are created when lava tubes (sometimes up to 17 miles long) collapse. Lava tubes are created when flows of lava cool on the outside and lava continues on in the interior. It leaves a hollow tube with walls several feet thick. Over time the walls collapse and leave an access point for all kinds of wildlife and vegetation to make their home. Kenny's dad decided to traverse through some of these caves. The lava is very sharp and the footing is difficult; I don't know that I would have tried it.