Wednesday, March 8, 2017

Idaho Lava Rocks

Traveling to Craters of the Moon National Monument in Idaho is a genuinely beautiful experience on a nice sunny day. The unique, almost barren looking landscape of ancient lava flows resembles scorched Earth from distant vantage points. We stopped several times for photos along the way and managed to find two interesting specimens close to the side of the road a few miles from the park boundary.

Seeing lava fields here for the first time is definitely a bit surreal on multiple levels. Vast and concentrated fields of burnt rock surround roadways on the way to the park and in some places on both sides of the road. This makes the naming of the monument aptly appropriate as the escarpment looks like something straight from the moon or another world. Given the distance away at the time, we believe the rocks found are likely tephra material ejected from the Great Rift during the area's last known eruption phase.


Each volcanic rock specimen is very porous, with one rock a little more dense than the other. The first example is very light pumice material and seems to resemble perforated wood grain upon close inspection. Char marks are visible on all sides and holding the volcanic rock is like holding a significant part of local history.

The second lava rock specimen is more dense than the first with much smaller pockets and features a well defined soot coating around the edges. It is a fraction of the size of the first though still with its own unique character. Comparing these two rocks tells two very different, yet similar, stories about how they were formed over 2000 years ago.

It's easily understood how common lava rocks in nature really are by the frequency of volcanic eruptions around the world over time and large amounts of ejecta spraying across the countryside during violent eruptions. There is another, more modern clue, which is the use of readily available lava rock for decorative landscaping purposes. The same stones endured a volcanic crucible, formed by fire, and cast into the air by one of nature's most powerful forces.