Thinking about Rocks and Time (Trail of Two Forests)

There’s something surreal about rocks that clearly show they were once liquid. Reading about lava flows is one thing. Sure, it says the rock was liquid, and I don’t doubt it. But getting up close to a rock, with all of it’s solid hardness, and finding a curved and rippled surface not unlike some cake batters kind of puts it in perspective. Once upon a time, this solid surface moved like water.
tree mold, Trail of Two Forests
You can see the ripples in this photo, at about the 2 o’clock position on the tree mold.  Roughly 2000 years ago, Mt. St. Helens erupted lava which engulfed a forest.  Even as the trees burned, they were still cooler than the lava, causing it to solidify around the trees.  The flow moved on, leaving molds of the trees behind, sometimes with detailed impressions of the bark captured in stone.

The idea of Mt. St. Helens erupting lava is strange to me.  I know that all our Cascade volcanoes are composite volcanoes, built of multiple layers of various ejecta, sometimes ash, sometimes lava.  Still, because the 1980 eruption was so heavily ash-dominated, it’s been easy to think that that’s what Cascade volcanoes do.  It’s probably important to compare the south side of the mountain with its lava-based landmarks with the blasted northern face.  One mountain, multiple expressions.

Still, it’s surreal.  Humans aren’t good at thinking in geologic time.  Our lives are too short to really grasp the scale.  This is a hole that’s 2000 years old. (Why isn’t it more full of debris?)  Before the hole there was a tree who had lived long enough to gain many inches in diameter, which stood on soil built up after previous eruptions, which built a mountain on rocks pushed onto the margin of the North American continent at a time when that landmass was more tropical than today.  I know this.  But it’s only by seeing and experiencing that I begin to understand it, that the relative scale becomes clearer.

It’s an understanding that is simultaneously depressing and liberating.  I am so small.  Life goes on, with fragile mosses reclaiming an inhospitable basaltic landscape.




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