PLEASE NOTE:
*
CCNet, 30 November 1999
-----------------------
QUOTE OF THE DAY
"Scientists have long realised that
Earth is at risk from rocks
from outer space. However, their
warnings went unheeded until two
recent Hollywood films, Armageddon and
Deep Impact, showed Earth
being ravaged by such impacts. The
publicity prompted scientists
at the British National Space Centre
(BNSC) to investigate the
risk, and their report is said to have
startled Sainsbury into
action. It warns that the chances of
such an impact are far higher
than that of a big nuclear incident and
that it would have much
more serious consequences."
--
THE SUNDAY TIMES, 28 November 1999
(1) BRITAIN PLANS ARMAGEDDON CENTRE AS COMET SHIELD
THE SUNDAY TIMES, 28 November 1999
(2) ROBOT JOINS THE POLAR METEORITE HUNT
MSNBC Space News, 28 November 1999
(3) UNDERSEA VOLCANO
Physics News <physnews@aip.org>
(4) RECOVERY AFTER THE END-PERMIAN MASS EXTINCTION
R. J. Twitchett, UNIVERSITY OF LEEDS
(5) THE EARLY AND LATE JURASSIC MASS EXTINCTIONS
P.J. Harries & C.T.S. Little, UNIVERSITY
OF S FLORIDA
(6) BENTHIC EXTINCTION & RECOVERY AT THE K/T BOUNDARY
E. Hakansson & E. Thomsen, UNIVERSITY OF
COPENHAGEN
(7) CONTINUITY ACROSS THE K/T BOUNDARY
C. Heinberg, ROSKILDE UNIVERSITY CTR
(8) SILICA-SECRETING BIOTA & MASS EXTINCTIONS
G. Racki, SILESIAN UNIVERSITY
=================
(1) BRITAIN PLANS ARMAGEDDON CENTRE (sic!) AS COMET SHIELD
From THE SUNDAY TIMES, 28 November 1999
http://www.the-times.co.uk/news/pages/sti/99/11/28/stinwenws01031.html?1986266
Jonathan Leake and Mark Macaskill
NOW new Labour will save the world. Lord Sainsbury, the science
minister, plans to build an Armageddon institute (sic!) in
Britain to
track and destroy comets threatening the Earth.
The centre, which would probably be sited in Northern Ireland,
would be
tasked with tracing the courses of hundreds of thousands of rogue
rocks
whose orbits cross the Earth's, and then working out the chance
of a
collision. It could thus draw up plans to save the world by
destroying
them or pushing them off course with nuclear weapons.
Scientists have long realised that Earth is at risk from rocks
from
outer space. Such impacts have been credited with destroying the
dinosaurs 65m years ago and with other mass extinctions. However,
their
warnings went unheeded until two recent Hollywood films,
Armageddon and
Deep Impact, showed Earth being ravaged by such impacts.
The publicity prompted scientists at the British National Space
Centre
(BNSC) to investigate the risk, and their report is said to have
startled Sainsbury into action. It warns that the chances of such
an
impact are far higher than that of a big nuclear incident and
that it
would have much more serious consequences.
It points out that Britain has spent billions to reduce the
theoretical
risk of a serious nuclear accident to less than one every million
years. By contrast, says the report, the Earth has been hit by
meteorites several times this century and only a relatively small
amount of money is needed to detect and destroy those that could
pose a
threat in future.
The observatory would cost about £500,000 to set up and a
similar
amount in annual running costs, says the report. BNSC insiders
say the
most likely site would be at the Armagh Observatory, part of
Queen's
University, Belfast, which has considerable expertise in
understanding
the dynamics of the solar system. It is understood that Sainsbury
would
want France, Germany and Italy to help fund the project and
supply
expertise.
Sainsbury said: "I take this very seriously and have asked
experts to
advise me on what contribution Britain can make. I believe
an
international approach would be best."
Others say that the move is long overdue. "We are not alone
in being
concerned about this problem," said Professor Mark Bailey,
director of
Armagh Observatory. "America has already set up an
observatory to
detect Earth-threatening rocks and meteorites, and Japan is
building
two dedicated telescopes. We would work closely with both
countries."
Bailey will ask the Particle Physics and Astronomy Research
Council for
money to set up a robotic telescope on a mountain in the Canary
Islands, to be controlled by astronomers in Armagh. It would
systematically scan the skies for meteorites (sic!), feeding data
back
to Armagh for analysis.
One job for the team would be to calculate exactly where on Earth
a
meteorite (sic!) might strike. If efforts to deflect it failed,
astronomers would be able to warn governments to evacuate regions
at
risk.
Among the close encounters already experienced by the Earth this
century were a huge explosion above Tunguska, in Siberia, caused
by an
800-metre meteorite [~60 metre asteroid, BJP] detonating in the
atmosphere. It flattened hundreds [~2000, BJP] of square miles of
forest and would have devastated any towns if it had exploded
over
them.
In the 1930s two large meteorites reached the ground in Latvia
and the
Amazon, causing big craters, and in 1947 a meteorite composed
mainly of
nickel and iron impacted in Siberia, creating a 200ft-deep hole.
Duncan Steel, an expert in comets and meteorites, who heads the
space
technology group at Salford University, said the threat from
space was
real. He added: "Life has existed on Earth for 3.8 billion
years, but
the course of evolution has been altered time and again by
asteroid
impacts. At last a species has evolved which has the ability to
save
itself and ensure its future. That species is us."
Copyright 1999 Times Newspapers Ltd.
=============
(2) ROBOT JOINS THE POLAR METEORITE HUNT
From MSNBC Space News, 28 November 1999
http://www.msnbc.com/news/340170.asp#BODY
By Alan Boyle, MSNBC
Nov. 28 — A rock-hunting robot is being sent to
Antarctica on a
mission that will likely turn up the first meteorites discovered
by a
machine rather than a human. The project’s leaders hope the
techniques
will be put to use someday by free-thinking robots sent to other
planets.
THE 1,200-POUND Nomad robot is due to set out Monday on the first
leg
of its trip to Antarctica’s Elephant Moraine, one of the few
areas in
the world where meteorites from Mars have been found. The
temperature
at this time of year can rise to a balmy zero degrees Fahrenheit
(minus-18 Centigrade), but for humans, the wind can make it feel
like
it’s 40 below.
It’s no picnic for robots, either. The four-wheeled Nomad,
built by
Carnegie Mellon University’s Robotics Institute, has been
winterized to
keep its gas-powered electric generator from freezing up. During
its
outings in January, Nomad will have to use laser rangefinding
equipment
to make its way through the Antarctic whiteness. And even if
Nomad
finds a precious meteorite, it’s not allowed to pick the
rock up. That
will be left to John Schutt, an expert from the Antarctic Search
for
Meteorites program who will be accompanying Nomad’s handlers
in the
field.
So why do it? It’s a natural question, says Dimi
Apostolopoulos,
manager of the Nomad project.
"What we’re trying to do, really, is for the first time
— even by NASA
standards — to demonstrate autonomous and in situ
classification of
samples in the field," Apostolopoulos said. "Nomad has
the intelligence
todetermine whether to go into an area from a scientific benefit
point
of view."
That’s why NASA has funded the research project to the tune
of $1
million a year. January’s three-week campaign is the climax
of a
three-year effort that included field tests in Chile’s
Atacama Desert
in 1997 and Antarctica’s Patriot Hills last year.
LEFT ON ITS OWN
For the Patriot Hills test, researchers planted the meteorites
like so
much candy for an Easter egg hunt. This year, the human experts
will
scope out an area of the moraine where meteorites are present
— but
then Nomad will be left to its own devices. "If we operate
for a day
with no human intervention, we can think of this as a very
effective
result," Apostolopoulos said.
Copyright 1999,
MSNBC
============
(3) UNDERSEA VOLCANO
From Physics News <physnews@aip.org>
PHYSICS NEWS
UPDATE
The American Institute of Physics Bulletin of Physics News Number
459
November 29, 1999 by Phillip F. Schewe and Ben Stein
UNDERSEA VOLCANO. Like astronomers who team up to view supernova
eruptions at a variety of wavelengths, geophysicists have been
able to
mount an in-depth study of the eruption in January 1998 of the
Axial
Volcano, lying 1500 m underwater about 200 miles off the
Oregon-Washington coast (see figure at www.aip.org/physnews/graphics).
Axial, which is a large volcanic edifice lying along a rift zone
in the
Northeast Pacific where new ocean floor is being created, is one
of the
few places on the worldwide 60,000-km mid-ocean ridge system
(Iceland
and the Azores are other examples) where volcanic activity can be
monitored in real time. In this case the coverage consisted of
Navy
hydrophone arrays (listening for quakes rather than subs),
surface
ships, moored sensors, and instruments placed on the very summit
of the
caldera in anticipation of an eruption. The 1998 event is
chronicled
in a variety of ways in a series of articles in the December 1
and 15
issues of Geophysical Research Letters. For example, C.G.
Fox reports
(via on-the-spot seafloor measurements) a 3-meter drop in the
caldera
floor; Baker et al. provide the first in-situ observation
of the
water temperature change above an erupting rift zone
(constituting the
"largest vent field heat flux yet measured"); Embley et
al estimate
that up to 76 million cubic meters of lava were produced, modest
by
land volcano standards, but the largest outpouring in 20 years of
monitoring along the Juan de Fuca Ridge. (Robert Embley, Pacific
Marine
Environmental Laboratory, embley@pmel.noaa.gov,
541-867-0275.)
============
(4) RECOVERY AFTER THE END-PERMIAN MASS EXTINCTION
R. J. Twitchett: Palaeoenvironments and faunal recovery after the
end-Permian mass extinction. PALAEOGEOGRAPHY PALAEOCLIMATOLOGY
PALAEOECOLOGY, 1999, Vol.154, No.1-2, pp.27-37
UNIVERSITY OF LEEDS,SCH EARTH SCI,WOODHOUSE LANE,LEEDS LS2 9JT,W
YORKSHIRE,ENGLAND
Strata of the Lower Triassic Werfen Formation (Dolomites,
northern
Italy) record deposition in a wide range of palaeoenvironments
from
peritidal to outer ramp settings. This enables accurate
assessment of
faunal recovery following the end-Permian mass extinction by
eliminating facies-related effects. Extinction of the shelly taxa
appears to be rapid and occurs in the latest Permian Tesero
Oolite
Horizon. Disappearance of the various trace fossil taxa appears
to be
more gradual. Following the extinction, the lower and middle
Griesbachian are characterised by laminated sediments containing
low
diversity bedding plane assemblages. Ichnological, geochemical
and
sedimentological data show evidence of widespread low oxygen
conditions. Normally oxygenated waters return in the late
Griesbachian
and there is a moderate increase in tiering above and below the
surface. Macrofaunal and ichnofossil diversity decrease markedly
during
the Smithian, with the appearance of more terrigenous strata
possibly
reflecting an increased run-off and more brackish conditions.
Complete
recovery begins in the basal Spathian with an increase in tiering
above
and below the substrate. Crinoids and ammonoids appear for the
first
time in the Werfen Formation, and the ichnogenus Rhizocorallium
re-appears. Global correlation is hindered by poor
biostratigraphy in
the Dolomites region. However, on a broad scale it appears as
though
many of the palaeoenvironmental changes are repeated worldwide.
Current
available data suggest that the re-appearance of some trace
fossil taxa
(e.g. Diplocraterion, Rhizocorallium) may be globally
synchronous. (C)
1999 Elsevier Science B.V. All rights reserved.
============
(5) THE EARLY AND LATE JURASSIC MASS EXTINCTIONS
P.J. Harries*) & C.T.S. Little: The early Toarcian (Early
Jurassic) and
the Cenomanian-Turonian (Late Cretaceous) mass extinctions:
similarities and contrasts. PALAEOGEOGRAPHY PALAEOCLIMATOLOGY
PALAEOECOLOGY, 1999, Vol.154, No.1-2, pp.39-66
*) UNIVERSITY OF S FLORIDA,DEPT GEOL,4202 E FOWLER AVE,SCA
528,TAMPA,FL,33620
The early Toarcian (eTo) and Cenomanian-Turonian (C-T) mass
extinctions
are comparable from a wide range of scales and perspectives. From
a
broad standpoint, their similarities include: virtually identical
extinction intensity at the familial and generic levels,
widespread
basinal facies deposited during sea-level highstands, an overall
greenhouse climate, and anoxia as an important causal mechanism.
The
high-resolution, macroinvertebrate data analyzed here, consisting
of
stratigraphic ranges, diversity and abundance, point to
smaller-scale
similarities. The two events resulted in significant ecological
disruption and, in both cases, the biotic responses were very
similar.
Taxa inhabiting the upper water column were unaffected by anoxia
and
included ammonites and, in the eTo, belemnites. In addition,
epifaunal
taxa adapted to low-oxygen conditions, such as the buchiids,
posidoniids and inoceramids, flourished in the post-extinction
environment during the survival interval. As conditions
ameliorated,
the biota became more diverse and gradually began to resemble
pre-extinction biotas. Furthermore, the delta(13)C curves predict
the
end of the survival interval and suggest that the period
characterized
by carbon isotope excursions represent disrupted environmental
conditions. This points to the potential application of
delta(13)C as a
tool for determining the repopulation modes and timing for other
mass
extinctions. (C) 1999 Elsevier Science B.V. All rights reserved.
============
(6) BENTHIC EXTINCTION & RECOVERY AT THE K/T BOUNDARY
E. Hakansson*) & E. Thomsen: Benthic extinction and recovery
patterns
at the K/T boundary in shallow water carbonates, Denmark.
PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY, 1999, Vol.154,
No.1-2, pp.67-85
*) UNIVERSITY OF COPENHAGEN,INST GEOL,OSTER VOLDGADE 10,DK-1350
COPENHAGEN,DENMARK
Benthic extinction at the K/T boundary in the Danish Basin is
abrupt
and indistinguishable from the termination of Maastrichtian White
Chalk
deposition. The Danian benthic fauna - already fully established
in the
earliest Danian nannoplankton zone NP1 - is essentially an
impoverished
Maastrichtian fauna established through direct survival or
limited
evolution within well-established clades, already present in the
Maastrichtian of the Danish Basin. However, recovery of the early
Danian community is initially retarded. The transition is
illustrated
in some detail for the locality, Nye Kl phi v. Here the lower 2-3
m of
Danian strata (corresponding largely to the lower NP1 subzone)
contains
an extremely impoverished, highly unusual,'dead zone' community
dominated by bourgueticrinid crinoids associated with other
presumed
soft ground specialists and devoid of such important faunal
elements as
cyclostome bryozoans, brachiopods, calcitic bivalves, etc. Over
the
next metres the 'dead zone' fauna is gradually replaced by more
ordinary faunas, and about 6 m above the boundary the
characteristic
early Danian bryozoan limestone community is fully established.
(C)
1999 Elsevier Science B.V. All rights reserved.
===========
(7) CONTINUITY ACROSS THE K/T BOUNDARY
C. Heinberg: Lower Danian bivalves, Stevns Klint, Denmark:
continuity
across the K/T boundary. PALAEOGEOGRAPHY PALAEOCLIMATOLOGY
PALAEOECOLOGY, 1999, Vol.154, No.1-2, pp.87-106
ROSKILDE UNIVERSITY CTR,DEPT ENVIRONM TECHNOL & SOCIAL
STUDIES,DK-
4000 ROSKILDE,DENMARK
The paleoenvironmental change at the K/T boundary at Stevns Klint
is a
change from an upper Maastrichtian bryozoan bioherm environment,
with
different faunas from the bioherms and from the interbiohermal
basins,
to an early Danian environment comparable to the biohermal
basins,
except for a nearly complete lack of bryozoans in the lowermost
Danian.
The bivalves exhibit a drastic reduction in species number when
the
complete faunas are compared. However, a within-habitat
comparison
between the Maastrichtian interbiohermal basins and the Danian
shows an
increase in the number of infaunal species across the boundary. A
decline in the number of epifaunal species is related to the lack
of
bryozoans, acting as substrates for epibyssate bivalves.
Comparison
with other K/T boundary sections rich in marine mesobenthos, does
not
support the presence of general patterns in the faunal change at
the
boundary. (C) 1999 Elsevier Science B.V. All rights reserved.
=============
(8) SILICA-SECRETING BIOTA & MASS EXTINCTIONS
G. Racki: Silica-secreting biota and mass extinctions: survival
patterns and processes. PALAEOGEOGRAPHY PALAEOCLIMATOLOGY
PALAEOECOLOGY, 1999, Vol.154, No.1-2, pp.107-132
SILESIAN UNIVERSITY,DEPT EARTH SCI,BEDZINSKA ST 60,PL-41200
SOSNOWIEC,POLAND
High survival and at least regional blooms of siliceous marine
groups,
with coeval retreat of calcareous organisms, is known from the
Frasnian-Famennian (radiolarians, silicisponges) and
end-Cretaceous
(diatoms, radiolarians) mass extinctions. A strictly actualistic
approach to the palaeoecology of silica-secreting biota is of
limited
significance, especially for silica-enriched and oligotrophic
Palaeozoic epeiric seas and, in particular, during biotic
turnovers.
Adaptation among silica-secreting marine plankton has led toward
more
efficient utilization of shrinking dissolved silica resources
within
surface waters of Cenozoic oceans, as shown by both radiolarians
and
diatoms. This biosiliceous signal during the major biotic crises
is
mostly explained by a large-scale increase in
volcano-hydrothermal
activity during major plate-boundary re-arrangements, triggering
global
ecosystem perturbations. The cumulative stimulus favoured
siliceous
versus calcareous biota growth, deposition and preservation
because of
(1) a higher rate of input of silica and other nutrients,
promoting
eutrophication pulses, (2) a punctuated (or reversed) greenhouse
climatic effect, episodically coupled with (3) vigorous oceanic
circulation due to a variety of volcanogenic upwellings and
turnovers.
Siliceous communities, adapted to more eutrophic conditions, have
thrived in the stressed niches. On the other hand, expanding
anoxia and
nutrification may lead to a stepwise loss of deep-water niches
and
consequent selective decline of more specialized oligotrophic
radiolarians and other pelagic biota. By contrast, siliceous
faunas
experienced severe non-selective losses during the end-Permian
mass
extinction (recorded as a 'chert gap'). Thus, the greatest
environmental disaster of the Phanerozoic was driven by a unique
set of
killing factors, extremely effective for radiolarian
productivity,
e.g., due to the combination of a drastic volcanic winter with
expanding superanoxia. (C) 1999 Elsevier Science B.V. All rights
reserved.
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