A shaky September in Yakutat
By Ned Rozell
June 19, 2007
More than a century ago, eight prospectors were panning the glacial
sands near Hubbard Glacier when Earth starting shaking and never
seemed to stop. A few days later, they had survived a natural
phenomenon they probably should not have.
Geologists Ralph Tarr and Lawrence Martin, in the area a few
years later to study the marvelous glaciers, saw things like
mussels "resembling clumps of blue flowers" on rocks
20 feet above the ocean. They saw so much evidence of a giant
earthquake they interviewed a few prospectors in Yakutat and
included their stories in a 1912 government paper, "The
Earthquakes at Yakutat Bay, Alaska, in September, 1899."
A photo showing shoreline
uplifted during a massive 1899 earthquake near Yakutat. From
the 1912 USGS paper, "The Earthquakes at Yakutat Bay, Alaska
in September, 1899."
When Tarr and Martin arrived in Yakutat, prospector A. Flenner
was working as a carpenter there six years after the series of
large earthquakes, the biggest being a magnitude 8.0 that happened
on Sept. 10, 1899. Flenner had been panning for gold in the area
"Mr. Flenner stated in 1905 that after the first shock on
September 3 they rigged up a home-made seismograph, consisting
of hunting knives hung so that their points touched and would
jingle under a slight oscillation," Tarr and Martin wrote.
"With this instrument (rude, perhaps, but more delicate
than their own perception) they counted 52 shocks on September
10, up to the time of the heavy disturbance (the 8.0 earthquake)
that caused so much damage."
Another miner, L.A. Cox, was also at the scene.
"About 9 a.m. on the 10th we had a very severe shock (what
USGS later calculated as a magnitude 7.4 foreshock), so violent
that one could hardly keep his feet," Cox said. "The
low alder brush shook and bent like reeds in a gale of wind.
(Then, at) 1:30 p.m., we got the king bee of them all."
The king bee was a massive earthquake that shattered glaciers,
lifted areas of shoreline 47 feet out of the water, and caused
"the death of millions of individuals," Tarr and Martin
wrote. Those individuals were fish and crabs deposited on land,
and barnacles, mussels and other rock-clinging organisms thrust
high above the water level.
A model Lawrence Martin
made of the dynamic Yakutat area. From the 1912 USGS paper, "The
Earthquakes at Yakutat Bay, Alaska in September, 1899."
The prospector Cox further
described the big earthquake:
"The ground (was) cutting some of the queerest capers imaginable.
In addition to the circular motion of the preceding heavy shock,
it was waving up and down like the swells of the sea, only with
considerably more energy."
On glacial sands that often liquefy during a large earthquake,
the prospectors were lucky to survive the episode as natural
forces ate their camp and all their supplies.
"We ran from our tents, leaving everything behind, and were
never able to rescue anything from it after," prospector
J.P. Fults said. "Above us about 100 yards was a lakeThis
lake broke from its bed and dashed down upon our camp while we
ran along the shore and escaped its fury. This deluge was almost
immediately followed by one from the sea. A wall of water 20
feet high came in upon the flood from the lake and carried all
debris back over the undulating morianic hills.
"We protected ourselves from being carried away by tearing
up clothes and tying ourselves to the small alder trees growing
on the mountainsides," Fults said.
The remarkable part of this story is that no one died despite
the bad placement of the miners. Tarr and Martin attributed the
earthquake to the impressive tectonic activity researchers today
know as the Yakutat Block crashing into southern Alaska, giving
rise to the highest coastal mountain range on Earth.
"The cause of these shocks was undoubtedly the renewal of
growth in the St. Elias Range, one of the youngest and loftiest
of mountain ranges," Tarr and Martin wrote.
This column is provided
as a public service by the Geophysical
Institute, University of Alaska Fairbanks, in cooperation
with the UAF research community. Ned Rozell [firstname.lastname@example.org
] is a science writer at the institute.
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