quiet. It took another fifty years to uncover and interpret the regio
’s
seismic history. Geology, as even geologists will tell you, is not normally
the sexiest of disciplines; it hunkers down with earthly stuff while the
glory accrues to the human and the cosmic—to genetics, neuroscience,
physics. But, sooner or later, every field has its field day, and the
discovery of the Cascadia subduction zone stands as one of the greatest
scientific detective stories of our time.
The first clue came from geography. Almost all of the world’s most
powerful earthquakes occur in the Ring of Fire, the volcanically and
seismically volatile swath of the Pacific that runs from New Zealand up
through Indonesia and Japan, across the ocean to Alaska, and down the
west coast of the Americas to Chile. Japan, 2011, magnitude 9.0;
Indonesia, 2004, magnitude 9.1; Alaska, 1964, magnitude 9.2; Chile,
1960, magnitude 9.5—not until the late nineteen-sixties, with the rise
of the theory of plate tectonics, could geologists explain this pattern.
The Ring of Fire, it turns out, is really a ring of subduction zones.
Nearly all the earthquakes in the region are caused by continental plates
getting stuck on oceanic plates—as North America is stuck on Juan de
Fuca—and then getting abruptly unstuck. And nearly all the volcanoes
are caused by the oceanic plates sliding deep beneath the continental
ones, eventually reaching temperatures and pressures so extreme that
they melt the rock above them.
The Pacific Northwest sits squarely within the Ring of Fire. Off its
coast, an oceanic plate is slipping beneath a continental one. Inland, the
Cascade volcanoes mark the line where, far below, the Juan de Fuca
plate is heating up and melting everything above it. In other words, the
Cascadia subduction zone has, as Goldfinger put it, “all the right
anatomical parts.” Yet not once in recorded history has it caused a
major earthquake—or, for that matter, any quake to speak of. By
contrast, other subduction zones produce major earthquakes
occasionally and minor ones all the time: magnitude 5.0, magnitude
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