But there are 40-odd cinder cones of once-active volcanos clustered near the bucolic town of Boring, just east of Portland Oregon. These, and the related lava flows, are part of the Boring formation.
I am intensely interested in this Boring volcanic activity north of Beaverton in the upper left of this map, which is close to my house.
A few weeks ago I found a warm groundwater seep in the Park near my house and it made me think.
I approach problems by first assuming the most dramatic solutions and then working my way to the plainest explanation; sort of a reverse Oxxam’s Razor. An Oxxam’s Hammer, perhaps.
Please bear with me although the topic is Boring. (Trigger warning. Not the last pun)
So my first wild assumption was volcanic activity was warming the water. And look at that, lava flows in Oregon were just a few miles away, and were active as recently as 1.3 million years ago!
Not only that, fifty years ago, a heavy equipment operator’s bulldozer abruptly punched through rubble into a void while digging the foundation for St. Vincent’s Hospital, north of Beaverton, and found lava tubes there. It must have been a surprise to the contractor, who had to pour 6000 truckloads of cement into the void before setting the foundation. (the hospital is #16 on the diagram.)
A previously unknown volcano in Portland’s west hills had erupted a million years ago, and sent out lava tubes, that are fire-spewing tentacles at birth, and dangerous and intriguing geological features later.
When lava flows, the top, sides and bottom solidify, forming a tube, and the lava inside the tube flows until it runs out. Sometimes it leaves awesome caves behind. The diagram below shows how the tubes poke out the sides of a volcano.
However many lava tubes collapse or fill up with rubble and become hard to identify. On the surface, they look more like craters than caves. In my neighborhood we had 450 feet of silt pile up and blow in when Lake Missoula flooded 12,000 years ago.
The incoming floods of silt obscured many volcanic features such as tubes and even hid cinder cones. People die or are injured from falling into hidden lava tubes’ entrances.
All of the Western States had volcanos. Most have parks with lava tubes so it’s possible to visit one. Oregon has a Lost Lake, and the Rogue River, both of which drain and disappear for a fashion, into lava tubes.
Many lava tubes are several miles long. the Lava River Cave near Bend Oregon is a mile long. Lava tubes help keep Crater Lake full of water.
Most geologists assumed for many years that the volcanic Columbia basalt flows west of Portland were then covered by Volcanic sand and muck from massive flooding.
Then several 50 year old geology articles insisted that scientists found lava tubes on the west side of the Portland Hills, far from the Boring fields, and closer to my warm seep.
An local newsletter repeated a legend that some gardeners even farther west could feel cool air coming from the ground. Wouldn’t that be spooky?
The scientists found that “Boring” lava flows popped from tubes from the flanks of two 1000-foot volcano cones in the West Hills, and busted up through the Columbia basalt in spots.
I set out with the old geology magazine articles (The Ore Bin and Rubble) and old topo maps, seeking those lava caves, hoping for at least this:
Three of the original lava tube depressions are still visible on this topo map, just north of Barnes Road. There were five depressions on the 1961 topo. On the most recent map, all the depressions are smoothed out.
For some, this Bucket may disappoint worse than Al Capone’s vault. For those folks, I am linking to additional geologic studies of this vicinity. They rammed a train tunnel through these volcanic cones 30 years ago.
Please read the linked materials carefully. You’ll be tested tomorrow.
I am also alleging this Bucket is a deliberate follow-up to FF’s recent wonderful Bucket on earth sciences. That’s my story and I’m sticking to it. Well, it was an happy coincidence and inspiration.
When Covid goes away I will look up the technical journal articles of Squier, 1970, and Trimble, 1963, who are the primary sources on these lava tubes. I’ll also e-mail Professor Scott Burns who knows local geology and teaches at PSU.
By the time you are 70 your nearest hospital may be part of your Backyard. Therefore I claim jurisdiction to discuss geology in this vicinity since it’s my hospital that has lava tubes underneath.
The lava tube search continues!
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