I have a confession to make: I’m not really a geology person. I understand objectively why some people would consider it fascinating, and I sometimes wish I was one of those people, but whenever I actually try to read a book or watch a presentation about rocks and geologic history my mind starts to wander almost immediately.
Still, occasionally a particular geology concept will lodge itself in my brain anyway, and when that happens I feel very proud of myself for being able to point out some odd rock feature and give it a name. Case in point: columnar basalt. Whenever I’m driving around here and see these odd hexagonal columns of stone, I always think to myself “hey, columnar basalt!” and feel happy.
Basically, these structures form when lava cools relatively rapidly and contracts as a result. From Wikipedia: “While a flow can shrink in the vertical dimension without fracturing, it can’t easily accommodate shrinking in the horizontal direction unless cracks form; the extensive fracture network that develops results in the formation of columns… The size of the columns depends loosely on the rate of cooling; very rapid cooling may result in very small (<1 cm diameter) columns, while slow cooling is more likely to produce large columns.” The fact that these formations are so common around here attests to the area’s volcanic past.
So, to sum up, my entire understanding of the geologic history of eastern Oregon boils down to “volcanoes, woot!” and I’m pretty okay with that. But I really like columnar basalt. Because I know what it is.