Geophysicists study Earth’s core
Millimeter deviations from the expected wobble of the
Earth’s axis are giving geophysicists clues to what happens
1,800 miles underground, at the boundary between the Earth’s
mantle and its iron core.
A new theory proposes that iron-rich sediments are floating to
the top of the Earth’s core and sticking like gum to the
bottom of the mantle, creating drag that throws the Earth’s
wobble off by a millimeter or two over a period of about 18.6
years.
“The wobble is explained by metal patches attached to the
core-mantle boundary,” said Raymond Jeanloz, professor of
geology and planetary science at the University of California,
Berkeley. “As the outer core turns, its magnetic field lines
are deflected by the patches and the core fluid gets slowed down,
just like mountains rubbing against the atmosphere slows the Earth
down.”
The idea, first proposed by Bruce A. Buffett of the Department
of Earth and Ocean Sciences at the University of British Columbia,
also explains a peculiar slowing of seismic waves that ripple along
the core-mantle boundary.
Buffett laid out the theory at the December meeting of the
American Geophysical Union and in an article with Jeanloz and
former UC Berkeley post-doctoral fellow Edward J. Garnero, now at
Arizona State University’s Department of Geological Sciences
in Tempe, in the Nov. 17 issue of Science. Much of the work was
done while Buffett was on sabbatical at UC Berkeley.
Biologists uncover “˜missing
evidence’
Biologists at UC San Diego have demonstrated, in a study of the
songs and genetics of a series of interbreeding populations of
warblers in central Asia, how one species can diverge into two.
Their description of the intermediate forms of two
reproductively isolated populations of songbirds that no longer
interbreed is the “missing evidence” that Darwin had
hoped to use to support his theory of natural selection, but was
never able to find.
“One of the largest mysteries remaining in evolutionary
biology is exactly how one species can gradually diverge into
two,” said Darren E. Irwin, a biologist at UCSD who headed
the study, detailed in the January 18 issue of the journal Nature.
“This process, known as speciation, is very difficult to
study because it can take a great deal of time to occur.”
Biologists have generally learned about the divergence of
species by comparing many different species at various stages of
speciation.
“Ring species are unique because they present all levels
of variation, from small differences between neighboring
populations to species-level differences, in a single group of
organisms,” said Irwin.
Many lives still lost to breast cancer
Despite advances in early detection and treatment for breast
cancer, too many women in California are still losing their lives
to the disease, according to a report presented Jan. 18 to the UC
Board of Regents.
Although nearly 15,000 California women diagnosed with breast
cancer this year will still be alive 10 years from now because of
early detection and treatment, nearly 6,000 women who are diagnosed
this year will die during this decade, the report notes.
The statistics and analysis of the “Status of Breast
Cancer in California” was presented by Marion
Kavanaugh-Lynch, director of the California Breast Cancer Research
program, a UC systemwide effort.
“The information tells us that early detection alone will
not conquer breast cancer,” Kavanaugh-Lynch told the
regents.
Compiled from Daily Bruin wire reports.