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Wallowa County Chieftain
Wednesday, February 13, 2019
Wallowa County is home to the earth’s greatest volcanic eruption
By Ellen Morris Bishop
Wallowa County Chieftain
Wallowa County is a land
of superlatives. Le Gore
Lake is the highest in Ore-
gon. Hells Canyon is North
America’s deepest gorge.
And there is another, and
more global feather in our
cap.
We are the place that
unleashed the Earth’s great-
est known, mapped, lava
flow. Ever. This volcanic
eruption, 16.3 million years
ago, produced 9,500 cubic
MILES of basalt—enough to
build a wall a mile high and
a mile wide around the entire
continental United States.
What’s more, our County
Courthouse – and a lot of
other places in Wallowa
County — are built from the
ashy, glassy products of this
eruption. We know them as
Bowlby Stone.
The basalt lavas of this
greatest of all lava flows
known on Earth is called
the Wapshilla Ridge Flow,
named for its excellent
exposures on the massive
ridge between the Snake and
Salmon Rivers on the Idaho
side of Hells Canyon. This
huge flow was part of the
Columbia River basalts—
lavas that form much of our
landscape.
The explosive, ashy tuff
that would become Bowlby
Stone, erupted at the same
time from the same batch of
magma. The link between
the Bowlby Stone tuff and
the huge Wapshilla Ridge
lava flows was first recog-
nized last year by a team of
geologists Klarissa Davis,
John Wolff, and Owen Neill
of Washington State Uni-
versity, along with a col-
league from the Univer-
sity of Auckland in New
Zealand.
About 16.3 million years
ago what is now the Wal-
lowa Mountains and Zum-
walt Prairie were a lowland
of marshes, lakes, and riv-
ers. There were no Wallowa
Mountains, no Hells Can-
Ellen Morris Bishop
Large holes left in the solidified Wapshilla Ridge basalt
exposed in a road cut along the Imnaha Highway attest to the
huge amount of carbon dioxide and sulfur-rich gas brought to
the surface by this greatest of all known lava flows. Hot water
and steam interacting with the iron-rich tuff produced the red
and yellow oxidized iron minerals in the soil above the basalt.
yon. Things looked more
like a soggy version of
Kansas.
The Wapshilla Ridge
basalt flow was really a con-
tinuous series of flows and
eruptions. The volcanic vent
system was more than 60
miles long. Lava-gushing
fissures extended through
today’s Wallowas to Hells
Canyon and beyond. Intense
eruptions lasted more than
300 years (perhaps as long
as 1000 years) and slathered
60,000 square miles of Ore-
gon, Washington, and Idaho
in lavas averaging more than
100 yards thick. Additional
eruptions may have con-
tinued for at least another
90,000 years. It was the
greatest of all the Columbia
River basalt flows, and the
most voluminous eruption
yet documented and mapped
on Earth.
One vent — or “dike” for
the Wapshilla Ridge Flow
— a 30-foot wide swath of
basalt that cuts through the
much older granites — is
exposed in the Wallowas just
east of Maxwell Lake. Stud-
ies by Oregon State Univer-
sity’s Heather L. Petcovic
determined that this one vent
alone gushed almost a cubic
mile of basalt per day for 10
years.
But now we’ve learned
that the Wapshilla eruptions
were much more than just
basalt flows. WSU geolo-
gists Klarissa Davis, John
Wolfe, and colleagues found
that much of Zumwalt Prai-
rie, from Crow Creek to
Camp Creek, was also a site
of major eruptions.
The Zumwalt Prairie
eruptions were very, very
explosive.
If you stick a red-hot
poker into water you get an
instant burst of steam and
boiling water. The same
thing happens on a much
larger scale when red-hot
lava rising from deep in the
earth encounters lakes and
saturated ground near the
surface. Water boils. Steam
explodes. Hell breaks loose.
Geologists call this a “hydro-
volcanic eruption.”
When Wapshilla erup-
tions began on Zumwalt,
steam and churning, boiling
water literally tore the rising
lava into fragments and flung
the whole mess skyward.
Some lava chilled so quickly
that it literally became glass
rather than basalt. Much of
the fragmented lava erupted
at Zumwalt reacted with
water to become an oxidized
red-yellow clay-rich ash.
This seething mixture of
gooey volcanic ash, shards
of volcanic glass, and roiling
steam, was so hot that when
it finally landed the parti-
cles welded together into a
solid mass of soft, porous
rock. Geologists call this
kind of rock tuff. In Wal-
lowa County it’s known as
Bowlby Stone.
The volcanic hysterics
that produced the Bowlby
Stone occurred multiple
times throughout centuries.
Consequently, there are mul-
tiple Bowlby Stone-type
deposits that vary in colors,
textures, and composition.
You can find the welded tuff
of Wapshilla Ridge erup-
tions along Crow Creek, the
Imnaha Highway, and near
Marr Flat. Ashy deposits on
Ruby Peak, and a long-lost
quarry site up the Lostine
River, where the stones that
compose the Lostine Tavern,
Lostine School and Coleman
and Chrisman bank build-
ing in Wallowa originated,
may be remnants of those
eruptions.
Not only did the Wap-
shilla Ridge flow change the
landscape. It also probably
changed the Earth’s climate.
The global climate of
about 17-15 million years
ago, known as the Mio-
cene Climactic Optimum,
was somewhat warmer than
today. It coincides closely
with the entire period, 16.7
to 14 million years ago when
most of the carbon-diox-
ide-rich Columbia River
basalts erupted.
But at precisely the time
of the Wapshilla Ridge
eruptions, the global cli-
mate cooled by a degree or
two. The gases in Wapshilla
Ridge lavas were especially
rich in sulfur. Davis and
Wolff determined this by
analyzing the gas trapped in
tiny bubbles within mineral
grains in the Bowlby Stone
tuffs. They calculated that
the Wapshilla Ridge Flow
eruptions released about 300
billion tons of sulfur dioxide
into the atmosphere, along
with particulates. “This
would have been devastat-
ing regionally because of
the acid-rain effect from the
eruption,” Wolff said.
When a large quantity
of sulfur is injected into the
atmosphere, it blocks sun-
light, producing cooler
global temperatures. And so,
the eruption of the globe’s
mightiest lava flow here in
what would become Wal-
lowa County, not only
changed the landscape, but
likely cooled the planet for
a brief time as well. “It had
a global effect on tempera-
tures, but not drastic enough
to start killing things, or if
it did, it did not kill enough
of them to affect the fossil
record,” Wolff noted.
The next time you are at
the Wallowa County Court-
house, or any of the many
other grayish stone build-
ings here, take time to look,
really look, at a block of
the Bowlby Stone. Look
at its textures — elongated
blobs of bark basaltic glass
encased in a fabric of welded
gray ash. In most blocks you
can see a subtle pattern that
tells you which way the
wind was blowing as the
ash cloud came to rest. The
greatest known, mapped and
analyzed basalt eruption of
all time is right there in front
of your nose and at your fin-
gertips. No wonder Wallowa
County is such a powerfully
special place!
Enterprise Elks Lodge
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FEED
Saturday, February 23, 2019
5 pm to 8 pm ~ Cloverleaf Hall
Casino Night 8:00 pm
Donate a Dessert for the
Dessert Live Auction 6:30 pm
(Proceeds benefit the Casey Eye Clinic)
No Host Bar provided by
La Laguna Restaurant
5:00 pm till closing
Tickets at the Door
All-You-Can-Eat Crab - $37.00
Prime Rib & Cup-of-Crab -$37:00
Prime Rib Only - $25.00
Children 11 & under - $27.00
(All-you-can-eat crab)
All include: Cole Slaw, Baked Beans
& Garlic Bread
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