The Life of Northwest Landscapes:
From the Introduction of the forth-coming book: Field Guide to Pacific Northwest Geology: Timber Press.
The
Pacific Northwest is a region defined as much by its geology as by its
drippy or dry landscapes, its threatened salmon, its picked-over
forests, and its and proclivity for environmental activism. In general
parlance, the northwest includes the states of Oregon and Washington ,
although geology has never learned to color strictly within state
lines. Geologically, the Pacific Northwest is more defined by its
ranges and rocks, its heritage of volcanoes and accreted terranes, its
flood basalts and subduction zones. We are Mount St. Helens. We are
the Columbia River Gorge. We are sea-stack, Haystack,
tide-pool-festooned coastlines, bombastic volcanoes, basaltic
outpourings, and a collage of ancient, exotic islands, seamounts, and
ocean bottoms that have created North America’s newest land. Our
landscapes are scions of the seafloor and they represent the ultimate
in recycling. The Northwest’s environmental passions could well be
rooted in this landscape. Tom McCall’s beloved bottle bill may have
come to pass because, viewed from his ranch beneath the rimrock, a
distant Mt. Jefferson presented a looming message: All matter, even
rock, is re-used, reformatted, and reborn. And of such rebirth comes
greatness.
Our landscapes prosper on reusing, reformatting,
and remanufacturing. Cascade volcanoes recycle small amounts of
time-worn sea floor sediments, dragged down a subduction zone, melted
and re-invented as tiny, molecular components of new lavas. The
ancient sea floor appears in our Cascade lavas as invisible, chemical
components. We cannot pick up a chunk of Cascade lava and actually see
a fragment of sea floor basalt or a smudge of bottom ooze, any more
than a remnant of plastic milk jug can be seen in an Olefin carpet.
These components are entirely recombined. But we can detect their
presence through traces of chemistry—a few extra parts per million
boron, a bit more beryllium, than magmas that come purely from the
mantle. In many Cascade lavas, there are tiny, chemical remnants of
sea floor, caste back into daylight as volcanic rock. We build cities
on it. We build cities of it. We crush it for roads, and then follow
those roads to trails that lead us to intimacy with the great peaks,
with South Sister, North Sister, Mount Rainier, Crater Lake. All
supreme recyclers. All giants with lessons to teach.
Every
rock, with the possible exception of meteorites, is a chunk of
reformatted or remanufactured planet. The bedrock of the Northwest is
dramatically associated with this geologic recycling. Seattle rests on
glacial till gleaned from more ancient North Cascade rocks. Tacoma and
towns to its east lie astride volcanic debris—mudflows that brought
chunks of domes and lava flows from Mt. Rainier. Spokane nests in
channels carved and gravels abandoned by the great, ice-age Missoula
floodwaters, and straddles the northern fringe of Columbia River
basalts (lavas purged from the mantle, 10 miles beneath the city,) and
the much older granitic rocks of the Spokane dome (remelted, remastered
volcanic rocks of ancient, accreted terranes.) Portland sits atop
debris from the same floods of lava and water. Bend’s foundation is
the ashy residue of hot-breathed Cascade volcanoes, a fluffy concoction
of molten mantle and sea floor coughed up violently by a vanished
Cascade volcano some 3 million years ago Eugene is buttressed by
older, more staid Cascade lavas that form Skinner and Spencer
Buttes—but share the history of recycled and reformatted material with
their Cascade kin.
What makes the Pacific Northwest
geologically distinct from the neighboring Rockies, or Great Plains or
other western geographies, is this emphasis on re-birth and
re-invention. We are a landscape of exotic terranes, of once and
future volcanoes, of new starts for old things, of reconstitution and
rebirth. Of Westside rainforests, yes. Of Eastside bluebunch
wheatgrass, of canyons and powerful rivers. But we are also the
landscape where geology does not take life sitting down. Where being
run over, scraped off, and dragged into the mantle energizes uplift,
eruptions, and mountain-building. This is not the flattened landscape
of Kansas, or the tired hills of Pennsylvania, or Florida’s passive
margin. There is hope here, rebirth and recycling. It is in our
landscapes as much as within us.
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