Pahoehoe and 'A'a - Craters of the Moon

For an example of what happens when there is a crack in the earth's crust and lava flows out, head to Craters of the Moon.  Major events occurred around 2,000 and 4,000 years ago that covered the land with pahoehoe flows, cinder cones, lava tubes, and other volcanic formations.  Today 53,500 acres of this land is protected.  

Visitors can hike to the top of cinder cones, walk along pahoehoe flows, and venture into caves created by collapsed lava tubes. There are several loops that provide educational opportunities to learn about the various volcanic features present in the park.  I recommend visiting during the off season or be prepared to experience ground temperatures exceeding 110 degrees.