It was a fantastic experience, but I haven’t previously discussed it here mainly because of uncertainties regarding legalities and whatnot. (My mum’s a lawyer: paranoia is in my genes.) So, let it be stated: nothing I say on this blog represents the opinion of Craters of the Moon National Monument and Preserve, the BLM, the NPS, the Geological Society of America, GeoCorps, or the National Speleological Society and its internal organizations. Caves are a federally protected resource, and thus I’m not going to disclose any cave locations, names, or, really, more information than is necessary.
If you are in south Idaho and would like to visit wild lava caves, that’s great! First, get your gear, read up on White Nose Syndrome, and then visit the Shoshone Field Office to request a list of caves open to the public.
All that might seem kind of stern, but this is what happens when caves are destroyed:
The left picture is from a cave heavily vandalized for its entire length, most of it vile in content, all of it lacking in artistry. The right picture shows detritus left behind by people who were clubbing and shooting pigeons in a cave; we also found two dead barn owls this summer. During my internship, several damaged cave gates were discovered as well: not only is this blatantly disrespectful, but also incurs an expenditure of governmental time and money, and frequently results in other cave damage.
Should someone committing acts of this nature be found, legal action can be taken against them under the 1988 Federal Cave Resources Protection Act. FCRPA states, essentially, that caves are super-awesome resources that should be protected, through inclusion in federal land management planning and communication between land management officials, cavers, and visitors. It also outlines punishments for those who damage or remove items from the cave: up to one year in prison and a fine for first time offenders, and up to three years for second time offenders. (Since many cave restoration projects take longer than this, I think this is a pretty light sentence.)
Rampant destruction of a sensitive and delicate ecosystem annoys the crap out of me. Not only is cave vandalism destructive to life-forms, but it also damages scientifically valuable features, cultural artifacts, pollutes aquifers, and ruins the cave for other visitors. In addition, partying in caves is unsafe – I watched a sober, helmeted person get a concussion this summer. The addition of booze, much less drugs, could create a much more serious situation, and result in a risky rescue situation. Also, it should be noted: caves don't clean themselves – someone else has to.
Cave vandals make me irrationally angry.
Craters of the Moon is run jointly by the National Park Service (NPS) and Bureau of Land Management (BLM.) My position was with the BLM, and focused mainly on cave conservation: completing the process to ensure legal protection under FCRPA, placing outreach/educational signs, and conducting cave surveillance. Additionally, I met the local caving club (grotto) members, led several tours through the caves, compiled a long-winded informational guide for interpreters, and found caves whose locations had been lost.
I thought that, in the next couple of posts, I’d share some of the cool things I saw and learned this summer. Frequently, caves seem to be misunderstood, feared, and ignored by the general public: this is a shame, because they’re really scientifically valuable, and provide recreational and educational opportunities for people of all ages, sizes, backgrounds, and experience levels.
(Unless otherwise noted, these pictures are from Craters of the Moon.)
The most common process for a lava tube’s formation is thus: a smooth, laminar flow of pahoehoe lava travels across a landscape with a certain slope – not too steep, or it will turn into a’a lava, and not too shallow, or it will fail to flow. (I’ve been told between .5 and 1.5 degrees: the validity of this is uncertain, however.) Frequently, these lava flows will form channels, as seen in the above picture from Jordan Craters, OR. As the lava flows in these channels, it begins to form chunks of crust: these raft along the flow, stick to the sides, and bunch up against one another. Eventually, a roof is formed over the channel: this continues to cool and thicken, while the lava underneath is still flowing. Frequently, the lava in the tube will cool and block the tube; if the flow is diverted or ceases, the lava may flow out, leaving behind a lava cave.
As the lava cave cools, the molecules in the lava are pulled towards one another, causing the lava to cool and contract. (This is standard for all liquids as they freeze, with the notable exception of water.) As it contracts, cracks form: it you’re lucky, a spot in the cave roof is weakened enough to collapse. This creates skylight entrances into the tube, like the ones in the above picture from Lava Beds, CA. (Skylights can also be formed when a section of roof fails to cool, although I have yet to see an example of this at a lava cave.) Skylights provide access to the cave for both organisms and cavers.
This is a good example of a primary lava tube: it has a simple oval shape, indicating that a secondary flow hasn’t travelled through and eroded the floor. This cave also had very few features, which can indicate that there were few lava flows in the tube. In places, we saw chunks of pahoehoe that stuck to the walls as the flow cooled; however, the majority of the floor was thickly covered with fine sediment. Uptube, it was possible to see where loess from the surface was washed in with small rocks: these quickly settled out, and, at the downtube end, blocked the passageway. We followed an old record to this area on my last field day, and it really panned out: we found seven caves, all erupted from the same vent. It was a pretty great way to end my internship.
This is the granddaddy of caves in the area: it’s the longest, and contains some really unique features (and some Silver Sage Grotto members for scale.) On the left, you can see an area where a secondary flow travelled through the cave, thermally eroding down the floor in the process, and thus increasing the tube’s height. This picture also shows a feature called benches/curbs/ledges: these show that a secondary lava flow travelled through the original tube, cooling onto the sides in the process. Benches frequently are characterized by their rectangular cross-sections, but they can have different shapes: in the right picture, you can see how there are benches stacked atop one another, and undercut at the bottom by a final flow. Also, the top of the right picture shows an spot in this cave where the secondary flow began to roof over, in a similar fashion to the creation of the original tube, creating a multi-layered tube. Depending on how you count, this lava tube has between three and seven levels.
These two pictures are from my favorite grotto trip: we rappelled into a lava lake through a gas vent. As the lava in the lake cools, it contracts and cracks (much like the infamous columnar joints,) creating a sunken lake. The left picture shows what may have been the original level of the lake, and a caver perched on its present level – quite the change! The right picture shows how the lake cracked and collapsed as it contracted. This was a great cave!
These are great examples of some important mineral deposits inside lava caves: gypsum, on the left, and calcite, on the right. These form as water drips through cracks in the cave’s roof, eroding it and picking up calcium and carbon. When this reaches the cave, the water evaporates, leaving behind the mineral. The calcite is a type of formation called coralloids, or popcorn.
Caving isn’t all cool rocks, however: sometimes, the rocks really suck. As the pahoehoe flow in the tube begins to cool down, it begins transforming into a’a: this can create a clinker floor, such as the one in the left picture. Most people know that clinkers are kind of lame to walk over, but only after belly-crawling over them do you truly realize just how painful they can be. (I lost two shirts while at the Northwest Caving Association regional in Bend!)
I had a great time this summer, learning first-hand about lava caves, lava fluid dynamics, cave management, and the BLM. The cavers in the area were really a treat, and the caves were fantastic!
I have another post about Idaho's lava tubes here.
1 comment:
This looks like a fun and great experience. Lava tubes are so different than other caves. Crawling on clinkers is never fun. Sure look forward to more of your summer adventures. Now what's happening over the winter?
Post a Comment