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.

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I live off this map to the left (west of Beaverton). 

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.

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This tube (Kazumura, Hawaii) is almost 41 miles long. 

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.