Two Violent Earthquakes hit coast of Baja and Rancho Palos Verdes California
13
December, 2012
California
– Two violent earthquakes hit the southern cost of California this
Friday morning at approximately 2:30 a.m. The first to hit was a 6.4
magnitude quake 262km SSW of Avalon, California the second quake was
a 6.1 magnitude reading with an epicenter 142km SW of Avalon,
California.
According
to the U.S. Geological Survey, the Mag: 6.4 – Depth: 10 km – off
the west coast Of Baja California – and the 6.1 magnitude
earthquake. 175 km from Rancho Palos Verdes, CA, United States.
Witnesses
in Anaheim say they felt a slow smooth whirlpool rolling shake.
Another witness in Ocean Beach, San Diego, was quoted as saying “Been
through many, this was the longest feeling one, my 2nd story 100 year
old apt, the floor swayed and twisted.
In
Hillcrest they’re saying they felt a strong seemingly long quake.
Inglewood
says “It was crazy it didn’t wake me up but the dog did.
Pico
Rivera, say they felt a subtle sway and shake. Lamp and windows
shook.
Coronado
witnesses say nothing fell off walls but certainly the house shook.
here
in San Diego, just felt my couch shaking from that quake a little
while ago… very eerie!
Folks
in La Jolla say they felt a gentle shake.
Spring
Valley witness says it woke her up.
An
Anaheim witness told us she was awake for odd reason then started
feeling the earthquake. She says it frightened. In her words: “I
hope the world doesn’t really end.
There
were many many more disturbed by these two quakes.
Earthquake
shaking in the eastern United States can travel much farther and
cause damage over larger areas than previously thought, but these
quakes were south west of that part of the U.S.
U.S.
Geological Survey scientists found that last year’s magnitude 5.8
earthquake in Virginia triggered landslides at distances four times
farther—and over an area 20 times larger—than previous research
has shown.
There
are no reports of damage or lost of life.
While
we were yet compiling this report another 5.1 quake hit the southern
coast of California.
The
Guardian Express will update you as soon as we have more information.
Scientists find dome of ‘violent’ submarine volcano off the coast of Baja, California
13
December, 2012
Scientists
have discovered one of the world's weirdest volcanoes on the seafloor
near the tip of Baja, Mexico.
The
petite dome — about 165 feet tall (50 meters) and 4,000 feet long
by 1,640 feet wide (1,200 m by 500 m) — lies along the Alarcón
Rise, a seafloor-spreading center. Tectonic forces are tearing the
Earth's crust apart at the spreading center, creating a long rift
where magma oozes toward the surface, cools and forms new ocean
crust.
Circling
the planet like baseball seams, seafloor-spreading centers (also
called midocean ridges) produce copious amounts of basalt, a
low-silica content lava rock that makes up the ocean crust. (Silica,
or silicon dioxide, is the main component of quartz, one of the most
common minerals on Earth.)
But
samples from the newly discovered volcano are strangely rhyolite
lava, and have the highest silica content (up to 77 percent) of any
rocks collected from a midocean ridge, said Brian Dreyer, a
geochemist at the University of California, Santa Cruz. The results
were presented last week at the annual meeting of the American
Geophysical Union. [50
Amazing Volcano Facts]
'A
total surprise'
Researchers
with the Monterey Bay Aquarium Research Institute (MBARI) discovered
the volcano this spring, during a three-month
expedition to
the Gulf of California, the warm stretch of water that separates Baja
from mainland Mexico. A remote-control vehicle explored the volcano,
which is 7,800 feet (2,375 m) below the surface, and brought samples
back to the ship.
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"When
we picked up the rocks and got them back on the ship, we immediately
noticed that they were very low density, and they were very light,
glassy and gray. They were not the usual dark, black, shiny basalts,"
Dreyer told OurAmazingPlanet. "So we immediately knew that
something was unusual."
The
volcano is primarily rhyolite and a silicic lava called dacite, said
MBARI geologist Jennifer Paduan. "To find this along a midocean
ridge is a total surprise," she told OurAmazingPlanet.
Boulders and blocks the size of cars and small houses littered the steep slopes of the dome, the robot's video camera showed. The gravelly debris is made of lava that resembles the ragged surface of a'a (rough, rubbly or blocky lava). The flows would have been deposited via large, avalanchelike deposits, Paduan wrote on the expedition's blog. A few ridges were composed of very strange, steeply dipping, lineated flows very different from the pillow-style appearance of deep-sea basalt, she wrote.
The
researchers don't yet know how the age of the volcano because their
samples haven't finished undergoing the necessary tests. The dome is
probably several thousand years old, MBARI geologist David Clague
said in an email.
Could
it go boom?
Of
more concern is the evidence for explosive volcanism, which is
typical of rhyolite volcanoes, Paduan said.
"It's
only 100 kilometers [60 miles] from land. When the sun is setting,
you can see Cabo," she said. Both the Baja Peninsula and
mainland Mexico near Alarcón Rise have cities and luxury resorts.
The Gulf
of California is also home to endangered sea life.
Rhyolite
lava carries more gas and volatiles (things that are likely to cause
explosions) than basalt, and when magma meets water, it vaporizes
instantly, driving an even more explosive eruption.
"There's definitely explosive deposits there, and that is of extreme concern,
given that the ridge is so close to land and the tsunami potential of
a big explosion there," Paduan said. "We don't know how
explosive, and that is something we are definitely trying to figure
out."
The
researchers also found Pele's seaweed, or limu o pele, at another
location on the 30-mile-long (50 km) ridge. These are little
fragments of lava formed from explosive magmatic gas bubbles that
implode when they hit cold seawater. "We did find evidence of
mildly explosive eruptions on the ridge," Paduan said.
Why
is it there?
Rhyolites
have been found on spreading centers, but only above hot spots, such
as in Iceland and the Galapagos Islands, Dreyer said. Hot
spots are plumes that
bring magma to the surface from deep within Earth's mantle. There is
no hot spot under the Alarcón Rise, he said.
Rhyolite
lava typically occurs only on continents, such as in Mount
St. Helen's growing
dome in Washington. One possible explanation for the bizarre
composition of the Alarcón dome is that continental crust snuck into
the molten rock below — the spreading center is young, and
continental crust lies close by. But tests of different isotopes
(versions of elements with differing numbers of neutrons in the
cores) in the lava samples revealed no evidence of contamination by
continental crust, Dreyer said.
Another discarded idea was that a cold spot underlying the ridge cooled and crystallized the magma chamber that fed the volcano, leaving only a high-silica melt behind. The team's current hypothesis is that the magma source had a high concentration of volatiles like water, sulfur and chlorine, maybe from an influx of seawater.
"It's
a work in progress, but we have found some of the glassy volcanic
debris surrounding this feature has water concentrations of up to
eight percent, which is pretty unusual for a spreading center,"
Dreyer said.
The
Alarcón Rise drifts apart at a relatively slow 2 inches (5
centimeters) a year. The segment is bounded by the
Pescadero transform
fault to
the north and the Tamayo transform fault to the south, and is the
northern extension of the East Pacific Rise. The vast majority of
lava flows along the ridge are basalt. The rhyolite dome is about 5.5
miles (9 km) south of the Pescadero transform fault.
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