12
new volcanoes discovered in Southeast Alaska
In Alaska, scores of volcanoes and strange lava flows have escaped scrutiny for decades, shrouded by lush forests and hidden under bobbing coastlines.
1
June, 2013
In
the past three years, 12 newvolcanoes have
been discovered in Southeast Alaska, and 25 known volcanic vents and
lava flows re-evaluated, thanks to dogged work by geologists with the
U.S. Geological Survey (USGS) and the U.S. Forest Service. Sprinkled
across hundreds of islands and fjords, most of the volcanic piles are
tiny cones compared to the super-duper stratovolcanoes that parade
off to the west, in the Aleutian Range.
But
the Southeast's volcanoes are
in a class by themselves, the researchers found. A chemical signature
in the lava flows links them to a massive volcanic field in Canada.
Unusual patterns in the lava also point to eruptions under, over and
alongside glaciers, which could help scientists pinpoint the size of
Alaska's mountain
glaciers during
past climate swings.
"It's
giving us this serendipitous window on the history of climate in
Southeast Alaska for the last 1 million years," said Susan Karl,
a research geologist with the USGS in Anchorage and the project's
leader. [Image
Gallery: Alaska's New Volcanoes]
Volcano
forensics
The
project kicked off in 2009 as part of an interdisciplinary effort to
better understand volcanism in Southeast Alaska, Karl said.
The
team's first result, from a volcanic pile about 40 miles (70
kilometers) south of Mount Edgecumbe, was an intriguing match in time
to the panhandle's biggest volcano. The team planned to test if the
two were related, sort of a geologic genetic test. But even though
the two volcanoes had erupted at about the same time in the past,
their chemistry was wildly different. It was like one volcano was a
freshwater fish and the other came from the salty ocean. And what
really captured the geologist's attention were signs that the little
volcano squeezed out lava that oozed next to glaciers.
"That's
when we realized we had a whole new kind of volcano separate from
Mount Edgecumbe," Karl told OurAmazingPlanet.
Lava
chemistry holds
forensic clues that reveal what was happening in Earth's crust and
mantle when the magma formed. The unusual chemistry sent Karl and her
collaborators hunting for more rocks to test. This meant days-long
backpacking trips into remote wilderness or submersible dives to
underwater volcanoes.
Not
only did they find the same unique chemical signature at other sites,
the team stumbled upon new volcanoes overlooked by earlier mappers.
"We're
convinced now there's probably a whole bunch of green knobs out there
covered with timber that may be vents that may have never been
mapped," said James Baichtal, a geologist with the U.S. Forest
Service based in Thorne Bay, Alaska, and a project leader.
Connection
to Canada
Now
comes the CSI twist. All of these newly tested lavas in Alaska are
kissing cousins to volcanoes
in Canada,
such as Mount Edziza, which last erupted about 10,000 years ago.
The
connection makes perfect sense, Karl said. "I'm actually
surprised no one has hypothesized it before," she said. "It
made total sense that this volcanic province would extend across
Southeast Alaska, and now I have the data to show that's the case."
Little
known outside of Canada, Mount Edziza is part of the Northern
Cordilleran Volcanic Province, a broad swath of volcanoes and hot
springs some 1,250 miles (2,000 km) long and about 375 miles (600 km)
wide.
Karl's
big picture meets approval with scientists studying Canada's
volcanoes.
"I
knew there were volcanics to the west in Alaska, but I didn't know
they were nearly [this] extensive," said Ben Edwards, a
volcanologist at Dickinson College in Pennsylvania, who is not
involved in the project but has visited the new volcanoes with Karl
and Baichtal. "They have really found a lot more places than we
realized, but there's certainly no reason for them not to be there.
It makes a lot of sense."
As
in Canada's volcanic province, Southeast
Alaska's volcanoes and
hot springs line up as amazingly linear features. Here's why: The
tortured history of this corner of North America, a legacy of
collision between the North America and Pacific tectonic plates,
created a meshwork of leaky faults and fractures. Magma escapes from
Earth's mantle through this patchwork when forces pull on the crust,
opening space. The matching chemistry also hints that magma in both
regions comes from a similar mantle source.
"It's
always fun to discover a new vent; it's fun to find a fossil, and
then to be able to understand why it's there is always very
satisfying," Karl said. "That's what makes scientists
tick."
Strange
new finds
Some
of the unusual finds Karl and Baichtal have uncovered include a maar
lying 295 feet (90 meters) underwater near Cape Addington, about 40
miles (65 km) west of Craig, Alaska. Maars are bomblike craters
blasted out when magma rising underground hits groundwater and
explodes. The maar is
about 13,800 years old, Baichtal said. Sea level was 394 feet (120 m)
lower when the maar formed.
The
latest find is an underwater volcano in Behm Canal, where hundreds of
thousands of tourists on cruise ships have sailed by New Eddystone
Rock, an eroded volcano. Behm Canal is dotted with cinder cones, both
onshore and below the water.
East
of Ketchikan, a basalt flow lapped onto a 42,000-year-old beach,
preserving shells, pinecones, pine needles and pollen. Barnacle
plates sitting on top of the lava are about 13,000 years old,
Baichtal said. The whole package now sits about 260 feet (80 meters)
above sea level, hinting at how much Earth's crust has bobbed up
since the last ice age.
"It
gave us how much isostatic rebound there is today. That's one of
those really great days in geology. You couldn't have written a
better script, and there's a lot of those kind of things coming out
of there," Baichtal said.
Volcanoes
and climate change
While
the volcanoes in Canada and Alaska have erupted for more than 10
million years, emerging data suggests that the last 3 million years
of glaciers growing
and retreating in Alaska and British Columbia also prompted many
small volcanoes to erupt, because the changing ice mass flexed the
Earth. This activated the fractures and made room for more magma to
rise.
In
Tolay Regional Park, north of Mount Edziza, Edwards is assembling
evidence of periodic eruption pulses in the last 2.5 million years.
"We
don't have a lot of the information yet, but it's consistent with
some sort of link between glaciations and volcanism. If you put 2 to
3 km [1.2 to 1.8 miles] of ice on that part of the cordillera and
then remove it pretty quickly, it may facilitate extension," he
said.
The
molten rock also has preserved impressions of bygone glaciers. Many
of the lava flows touched ice, leaving a distinctive
cooling pattern in
the chilled rock. By dating the glacially cooled lava flows,
researchers such as Karl, Baichtal and Edwards hope to better
understand how much land mountain glaciers covered during past
glaciations. About one-third of global sea
level risecould
come from melting mountain glaciers, but estimating their past size
is difficult because growing glaciers plow through evidence of their
predecessors.
Risk
of eruptions
Despite
its great size, the overall risk from eruptions in the Alaska portion
of the volcanic province is low, Karl said.
In
Canada, the volume of erupted lava is less than 240 cubic miles (100
cubic km) every million years in the last 2 million years. By
comparison, Hawaii's Kilauea volcano spewed 4,650 cubic miles (19,400
cubic km) in the past 300,000 to 600,000 years. [Big
Blasts: History's 10 Most Destructive Volcanoes]
The
most recent eruption in both countries was at the Blue River lava
flow in Lava Fork, which crossed the Alaska-Canada border 120 years
ago, according to new dating work by Karl and her colleagues.
"Even
though, theoretically, a volcano that erupted 120 years ago is an
active volcano, but because it's so remote there isn't any real
concern about it," Karl said.
However,
an eruption in 1775 killed a village of First Nations people in
Canada, though scientists aren't sure why. Lava didn't reach the
town, and some researchers suspect gas from the volcano may have
suffocated residents.
Karl
notes that an earthquake on the Fairweather Fault, a major offshore
strike-slip fault, presents a greater risk than a volcanic eruption.
"If something is rumbling and bubbling we have so much more
technology to become aware of it before it's a hazard, We can't
predict exactly when the Fairweather
Fault is
going to go, and that's a much larger hazard," she said.
With
15,000 miles of shoreline and hundreds and hundreds of islands to
explore, Karl and Baichtal think there are more volcanoes to discover
in Southeast Alaska.
"It's
a tough place to get around, but Sue and I just laugh at it. We will
never finish," Baichtal said.
Alert
level raised on Philippines Mayon volcano, after volcano exhibits
‘abnormal behavior’
1
June, 2013
MANILA,
Philippines (Xinhua) - The alert level on Mayon volcano in Albay has
been risen to Level 1 after it started exhibiting abnormal behavior,
a state agency said today.
The
Philippine Institute of Volcanology and Seismology (PHIVOLCS) said
that in the past 36 hours, three weeks after phreatic explosion on
May 7, fumes and crater glow were observed.
"PHIVOLCS
is raising the alert status of Mayon from Alert Level 0 to Alert
Level 1 as a precaution to the public that the volcano is exhibiting
abnormal behavior," it said in a Bulletin issued as of 5:00 p.m.
local time on Friday.
With this,
the agency is warning the public from entering the six-kilometer
radius permanent danger zone due to perennial danger of
life-threatening rockfalls, avalanches, ash puffs and sudden phreatic
or steam-driven eruptions.
Mayon's
alert level status may further change if significant changes in
monitoring parameters occur, it said.
PHIVOLCS
also advised residents around the volcano to remain vigilant and to
keep abreast of updates on Mayon's condition through local and
national officials.
On May 7,
Mayon's phreatic explosion killed seven people, four of them
foreigners, who were climbing the cone-like volcano.
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