Hey Cave Nerd! (part one)

We're going to try a change of pace this week. Instead of posting about the cheat day that came and went without notice, or the mostly carb-less Chinese food I had a few days after (no rice, no noodles, lots of veggies), I'm going to take a stab at answering some of the questions that have been generated by my friends and family. I am always flattered that the think enough of me to consider knowledgeable on one topic or another, when really, I'm just a guy that has issues turning his brain off when it finds something it reeeaally likes. The sword cuts both ways... any who, let's go! Oh and I'm not a trained geologist, so the following opinions are based on both independent research of the available data and personal observation, so feel free to correct me in the comments. If no one corrects me, then I will assume that, by default, I am the wisest caver that ever lived. You decide...

"What are pressure ridges in lava flows? How do they form and how big can they get?" - Steve 

That's three questions, Steve, but I'm game. Pressure ridges, strictly speaking, are surface deformations that happen in any non-viscous, flowing material that has cooled on the surface while free flowing material below continues to push the crusty upper section along. If the pressure applied by the fluid below is high enough all kinds of weird formations come to life.

Imagine you are baking a cake in a square pan and you remove it from the oven 1/2 of the way through it's timer and tip the pan at a a 20 degree angle; it will, of course bunch up near the bottom as the solid upper crust is compacted, while the runny batter underneath will continue to flow all over your lower hand and burn the shit out of you. Lava flows on a slope act the same way when obstructed or restricted by a channel of some sort, like a valley. On a large scale, pressure ridges on such flows are less likely to resemble concentric folds, like the molten cake batter now on your hands, or a bed sheet pushed against a headboard. Rather, they tend to crinkle into jagged angles, snap into bits and sometimes even bubble up into domes; hot rock has plasticity that is lost once cool, causing weak points and fractures that can't withstand the forces of the moving lava below. A robot does a good job at summing this up in this video.

I have seen pressure formations inside lava tubes that are very small, as in a foot or two, with the size and shape of a folded paper fan, to very large ridges that resemble harbor waves in heavy wind and frozen in time, but I have no idea if there is a maximum size - I'd imagine it would take a pretty massive lava flow to make them larger than 50', peak-to-trough. I'm not exactly schooled enough in the thresholds of that particular branch of chemistry or materials science to say with any certainty, though. But what I do know is that such formations, on the surface, can be very useful in divining where a flow originated, where a deep choke point was and where a flow was moving quickly, and thusly, where one should start a good hunt for a tube - but that's what you really wanted to know, isn't it?

"Do you know anything about the geology of Madras, Oregon" - Rae

Oh and how! There's so much going on in that area that it's best to start with the latest event for some perspective. The Bend/Redmond/Madras area has a rich history of being repeatedly covered in molten rock every which way one can imagine. As a matter of fact, in 1975, a fissure event took place in Redmond, when a sulfurous crack in the earth opened up just before I was spat out of hell itself at the speed of light.

Two non-fat cavers surrounding the weaker member of their herd, near Sawyer's Caves, Linn County, Oregon. Photo by Jarit Pitochelli  

When was your first time in a cave? - Tyler

When I was twelve, I went with my scout troop to Boulder Cave near Yakima, Washington and spent two days camping and exploring. Boulder Cave is a karst cave, which means that it's made by water dissolving soft rocks, like limestone. This cave is still being formed by the creek that runs through it and there are a few smaller caves near by. The rock formation that this cave was carved out of was a part of older sedimentary rock that was made underwater and far away from Washington and was added as an 'exotic terrain, ' as they call them; bits of islands and seamounts joined with granites from as far away as Mexico, all rammed into the coast and became part of North America as a whole, so it was a lot different that the basalt columns and scab lands that surrounded us on all sides on the eastern side of the state. We found squeezes and crawls, intersecting passages and back ways to the surface that I can't imagine even attempting as a fat adult. I had a lot of fun on that trip and I learned explicitly that one should always have at least one backup light, but it would be another 15 years before I went caving again.


Stay tuned for part two!!

 

*** The preceding words are a record of my personal journey and are not intended to replace or circumvent any recommend guidance provided by your health care provider. Before starting any life changing endeavor, such as a diet and/or exercise regimen, please start by having an honest conversation with your doctor. Links and references to products and services are unaffiliated - I don't make a dime from this blog. Don't be stupid - always be over prepared and never hike or cave alone and never, ever pour hot cake batter on your hands. As a matter of fact, cake is bad for you and should be shunned. Oh and please don't ask for cave locations. Believe me, if I can find them, so can you. ***


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