SCIENCE
NEWS
This Week
Tsunami
Disaster
Scientists model
the big quake and
its consequences
The magnitude 9.0 earthquake that struck
JI; LI, T. XUE/JOHNS HOPKINS UNIV.
the ocean bottom west of Indonesia on the
morning of Dec. 26, 2004, triggered several
tsunamis that killed an estimated 145,000
coastal residents and tourists, claiming lives
on shores even thousands of kilometers away.
Researchers are now analyzing the events
that led up to the destruction and modeling
their possible long-term effects.
The largest temblor in 40 years occurred
along a subduction zone where the immense
fragment of Earth’s crust known as the
India plate is forced beneath the Burma
plate at an average rate of 6 centimeters per
year. Analyses of seismic vibrations produced by the quake place its epicenter just
north of the island of Simeulue, which
lies about 150 kilometers off the western
PUMPED UP The sudden rise of seafloor
during the magnitude 9.0 quake of Dec. 26,
2004 (epicenter at star), caused tsunamis that
scoured coasts around the Indian Ocean.
W W W. S C I E N C E N E W S . O R G
coast of Sumatra. From there, at a depth of
18 km, the rupture raced northwest at supersonic speeds for more than 200 seconds,
says Chen Ji, a seismologist at the California Institute of Technology in Pasadena.
In all, slippage occurred along about
1,200 km of the interface between the tectonic plates—a distance that would span
California from north to south with about
100 km to spare. At some spots along the
interface, one plate may have slid as much
as 20 meters past the other, says Ji.
In the most-affected region, a broad
expanse of seafloor—and thus the sea above
it—was abruptly thrust upward as much as
5 m. The waves spilling away from that sudden bump raced across the Indian Ocean at
jetliner speeds, says Ji. The first tsunami
may have been 15 m high when it slammed
into Sumatran shores about 15 minutes
after the quake.
Satellite photos taken after the disaster
indicate that the tsunamis deposited beach
sand and soil or stripped away vegetation as much as 3 km inland
along much of Sumatra’s
western coast. As of press
time, the death toll in
Sumatra was estimated
to be in excess of
94,000. Sites farther
from the quake zone
experienced smaller but
nevertheless
deadly
waves. Particularly affected
were Thailand, which was
struck by tsunamis about 75
minutes after the quake occurred,
and Sri Lanka and India, which were
pounded by devastating waves about 4 hours
after the temblor. Death reached more than
5,000 km to African shores, claiming beachgoers and fishermen from Somalia to Kenya.
Notably, the Indian Ocean lacks a
tsunami-warning system like the network
of buoys and deep-sea instruments that
monitors earthquake and wave activity in
the Pacific Ocean (SN: 3/6/04, p. 152).
Although portions of the ocean floor rose
in many places as a result of the Dec. 26
quake, Ji’s geophysical models suggest that
the seafloor sank as much as 2 m in other
locales. Even some land was affected. Parts
of western Sumatra may have permanently
lost as much as 1 m in elevation.
Other effects of the temblor are subtle.
The sudden surge of the India plate downward, toward the planet’s center, slightly
altered the planet’s distribution of mass,
says Richard S. Gross of NASA’s Jet Propulsion Laboratory in Pasadena. Just as spinning skaters rotate more quickly when they
draw their arms inward toward their bodies, the Earth now completes its daily rotation in about 2.67 microseconds less time
than it did before the quake, according to
his calculations.
The region struck by the massive quake
had previously been identified as one of
about 80 areas likely to be stricken by a temblor of magnitude 7.0 or greater in the years
between 2000 and 2010. Between 1990 and
2000, the region near the Dec. 26 temblor’s
epicenter had experienced an above-average rate of earthquakes with magnitude 5.0
and above, says Donald L. Turcotte of the
University of California, Davis. —S. PERKINS
Beat
Generation
Genetically modified
stem cells repair heart
In experiments on guinea pigs, scientists
have used genetically modified human
embryonic stem cells to make a biological
pacemaker. The implanted tissue has kept
the guinea pig hearts beating after
their natural pacemaker cells
were destroyed.
The researchers, led by
Ronald A. Li of Johns
Hopkins University in
Baltimore, began with
unspecialized embryonic stem cells. The scientists genetically modified them to produce
green fluorescent protein.
When they separated the
cells into small clusters, the cells
began to differSTEM CELL POWER
entiate. Some
A cluster of genetically
clusters started
modified human
to beat, indicatpacemaker cells, about
ing the presence
200 micrometers across,
of heart-muscle
glows green atop an
cells and pacearray of tiny electrodes
maker cells. The
that detects its beats.
researchers then
extracted cells
from the beating clusters.
After transferring these cells into the animals, the scientists used a freezing probe
to kill the animals’ own pacemaker tissue.
Despite the loss of their natural pacemakers, the guinea pigs’ hearts continued to
beat. Close examination showed that the
rhythm was originating from the areas
where the human cells had been implanted.
Unlike battery-powered pacemakers, says
Li, stem cell–based pacemakers speed up or
slow down in response to drugs that alter
normal heart rate.
The researchers aren’t sure why the
guinea pigs’ immune systems didn’t destroy
the intruding human cells. According to Li,
the guinea pigs’ circulatory systems may
not have thoroughly branched into the
human cells and so the animals’ immune
systems may not have detected them.
Li’s study, to appear in an upcoming
JANUARY 8, 2005
VOL. 167
19
SCIENCE
NEWS
This Week
Temples
of Boom
Ancient Hawaiians took
fast road to statehood
Around 400 years ago, the residents of two
Hawaiian islands built stone temples at a
dizzying pace over the course of a generation or two, a new study finds. A construction boom of that kind and magnitude
reflected the surprisingly rapid formation
of a fledgling political state out of formerly
independent populations, investigators say.
Until now, many researchers assumed
that chiefs of various communities on the
islands of Maui and Molokai had directed
construction of temples over a span of
approximately 250 years.
New age estimates of the temples indicate that they were built within a much narrower window of time, say Patrick V. Kirch
of the University of California, Berkeley and
20
JANUARY 8, 2005
VOL. 167
STATE BUILDERS Dating of coral found in the remains of prehistoric Hawaiian temples
such as this one, shown from above, unveils a period of rapid state formation.
Warren D. Sharp of the Berkeley
Geochronology Center. The revised dates
come from pieces of sea coral that were
placed in special wall compartments during dedications of new temples.
Southeastern Maui contains the remnants of 30 temples that were constructed
within a 60-year span, between A.D. 1580
and A.D. 1640, Kirch and Sharp report in
the Jan. 7 Science.
The results coincide with the accounts of
native Hawaiians, recorded by 19th-century
Spanish missionaries, that a single leader
assumed control of at least two formerly
independent communities on Maui around
A.D. 1600. Anthropologists typically treat
such accounts as myths, Kirch says.
“I was surprised by the new dates for
these temples,” he remarks. “This is tangible evidence for the speed with which an
archaic state formed in Hawaii.”
An archaic state is a political system with
several social classes, as well as rulers who
claim power on the basis of their special
relationships to gods. Bureaucracies,
armies, and an early form of taxation first
emerged in archaic states.
Kirch and Sharp analyzed seven coral
offerings from what they regard as a representative sample of temples on Maui, as
well as one piece of coral from a large temple on Molokai. The preservation of delicate
branches and surface structures on the
specimens show that local people collected
live coral from shallow waters and
deposited it in a temple the same day, the
scientists say.
The researchers measured ratios of specific forms of uranium and thorium in the
coral specimens to calculate their ages. This
technique is more precise than previous
radiocarbon measurements of the ages of
wood and charcoal unearthed in the temples, Kirch and Sharp say.
State formation capped a period of population growth and expansion of agriculture on the island, Kirch theorizes. Pre-
historic settlers probably first reached Maui
around A.D. 1400.
A relatively speedy transition from villagebased life to stratified societies also occurred
in ancient Mexico, say Joyce Marcus and
Kent V. Flannery, both of the University of
Michigan in Ann Arbor. New radiocarbon
dates for sites in the Valley of Oaxaca indicate that only about 1,300 years elapsed
between construction of the oldest-known
ritual building, where village men gathered
for ceremonies, and the first state temple.
Marcus and Flannery’s results will
appear in the Proceedings of the National
Academy of Sciences. —B. BOWER
Reflections
on Insecticides
Mirror forms of
agrochemicals set risk
Mirror, mirror, on the wall, what’s the most
hazardous pesticide form of all? Such is the
question that scientists and regulators
should be asking as they evaluate the environmental effects of pesticides, new
research suggests.
Many molecules, like gloves of a pair, exist
in mirror-image forms. A team of environmental researchers has found that for some
insecticides, one mirror-image variant, or
enantiomer, is more toxic or degrades more
slowly in the environment than its counterpart does. Since pesticides typically are
mixtures of both enantiomers of a pair,
understanding the differences between the
two could lead to more-effective and less
environmentally hazardous agrochemicals.
Although different enantiomers of the
same molecule are identical chemically
and physically, they can have dramatically
different biological activities. “As a result,
they interact differently with microbes in
SCIENCE NEWS
KIRCH
Circulation, isn’t the first to use stem cells to
repair broken hearts, but it’s the first to do it
with genetically modified cells. The resulting
green glow made the human cells easy to
spot in the guinea pigs, but more important,
says Li, it’s proof that genetic modification
didn’t disrupt the cells’ development.
“Now, we can move on to something more
ambitious,” he says. His group has already
learned how to genetically alter human
pacemaker cells to fine-tune their firing
rates, though the scientists have yet to test
these modified cells in animals. Adjusting
the firing rate could be important because
ordinary pacemaker cells beat slowly when
implanted. The heart’s natural pacemaker is
a complex mixture of several cell types, Li
says, so it’s difficult to mimic its function
with any single, unmodified cell type.
Gordana Vunjak-Novakovic of the Massachusetts Institute of Technology, who
investigates techniques for growing replacement heart tissue, says that although many
groups are working to engineer heart tissue,
Li’s study stands out because it investigates
what happens after the engineered tissue is
implanted. Still, she cautions that much
work remains before heart-repair treatments can be developed for people. “We
cannot even complete a list of hurdles at
this time or predict how long it will take to
resolve some of the problems we are working on,” she says. —D. SHIGA