Hi,
This is one of those odd cases of knowledge being acquired
and lost and re-acquired in generational cycles, even in the so-called
"exact" sciences. The authors of this study say:
The ratio of 4He in terrestrial dust to the dust concentration itself
reveals a marked difference between the last Ice Age and the current
warm period. As . Gisela Winckler, head of the working group "Isotope
Tracers and Constant Flux Proxies" at L-DEO says, "the terrestrial dust
coming down on Antarctica during the Ice Age obviously is not the same
as that during warm periods. This may be due to the mineral dust
originating from different regional sources or to changes in weathering,
the process responsible for production of dust." Both scientists now
want to intensify their collaboration even further and investigate the
details of this phenomenon.
Just as there are those who decry impact explanations because
they are a form of "catastrophism," there was great resistance in the
mid-nineteenth century to the proposal that there had been "ice ages,"
dismissing the evidence because the whole idea was forbidden as
"catastrophism."
When we got over that, we learned a lot about ice ages, and one
of the paradoxes of ice ages is that they are times of global dessication
and dryness. Most of the great deserts were formed during ice ages.
At the peak of the last ice age, the sea level was 450 feet lower than
today.
I live at 613 feet above sea level and 1200 miles inland, but
storms have no difficulty bringing Gulf moisture over 1200 miles
of mostly flat land and dumping 40-odd inches of rain per year
on me. But if I were suddenly at 1063 feet above sea level and the
ocean was either hundreds of miles further away or at the foot of
a 400 foot cliff, I would get a lot less rain. To complicate the
problem, the temperature would be 10-15 degrees cooler; there
would be fewer rain storms and they would carry less water.
Southern Illinois would look a lot like eastern Colorado. Water
erosion would cease to be common; wind erosion would take
its place. The Dust Bowl of the Depression is a very weak
rehearsal of this effect. These effects would be world-wide;
I just used a local example.
The authors of the study say dust came from different regions
and from different weathering mechanisms and these changes need
to be investigated. There are mountains of studies 1880-1930 that
document these changes in great detail; they're sitting in geological
libraries and have never been put on the internet; go take a look.
An example of "knowledge being acquired and lost and re-acquired
in generational cycles..."
I ran across a reference the other day on a NASA website to
satellite studies "discovering" that the Sahara has underground
rivers in a vast connected web. Nope, not "discovered," not by
a long shot. Forty years (1890-1930) of difficult field work by
(mostly) French geologists discovered, traced, mapped, and
documented, in exquisite detail, not only the network of those
underground "rivers" in the Sahara but identified and mapped
their original surface watercourses. Yeah, satellites can probably
do a great deal to expand that knowledge and they should, but
field work in the Sahara is no picnic and if you do it, you should
get credit for it...
The Sahara, by the way, is not an "ice age" desert, but a modern
one. During the "recent" ice ages, it was wet, temperate, forested,
a paradise of game and good times for a substantial early human
population. The striking contrast between that picture and the
"Great Sand Sea" of today is a perfect example of what a huge
change a shift in weather and weathering can accomplish in a
relatively short time.
The current "southward march" of the sand is not a climatic
effect, but a physical one. Sand is generated continually in the
central Sahara and like any sandpile to which more sand is
added centrally, it spreads by gravity in any direction the slope
allows, in this case southward.
The Sahara is only an example of the complexity of ice age
desert change (in reverse). There are lots of geologists on this
List and they all know about "loess." There are parts of the world
where this wind-deposited fine soil (commonly called "dust")
is hundreds of feet deep (NW China, the Great Plains). These
are the soils rapidly emplaced in a cold, dry and dusty ice age
world.
Perhaps isotope studies can refine our knowledge of the
mechanisms of what an ice age world was like and what the
precise role of differing mechansisms of weathering were. By
all means, they should "investigate the details of this phenomenon,"
but this is not a "discovery," just really good work, of which
a lot has already been done.
And, for Rob Matson, I just want to point out, an ice age is
what happenes when you
----- Original Message -----
From: "Ron Baalke" <[EMAIL PROTECTED]>
To: "Meteorite Mailing List" <[email protected]>
Sent: Friday, July 28, 2006 12:26 PM
Subject: [meteorite-list] Cosmic Dust in Terrestrial Ice
http://www.awi-bremerhaven.de/AWI/Presse/PM/pm06-2.hj/060728Cosmic%20dust-e.html
Cosmic Dust in Terrestrial Ice
Alfred-Wegener-Institute
July 28, 2006
For the last 30,000 years, our planet has been hit by a constant rain of
cosmic dust particles. Two scientists from the Lamont-Doherty Earth
Observatory (LDEO) at Columbia University in New York and the
Alfred-Wegener-Institut (AWI) for Polar and Marine Research in
Bremerhaven, Germany, have reached this conclusion after investigating
the amount of the helium isotope 3He in cosmic dust particles preserved
in an Antarctic ice core over the last 30,000 years. They have shown
that this rare helium isotope in cosmic dust exceeds that of terrestrial
dust in ice by a factor of 5,000. Moreover, measurements of the amount
of 4He - a helium isotope much more common on Earth - in the Antarctic
ice strongly suggest a change of origins in terrestrial dust between the
last Ice Age and the interglacial warm period we currently live in.
In the current issue of Science, the scientists from New York and
Bremerhaven for the first time present chronologically resolved
measurements of the 3He and 4He flux of interplanetary and terrestrial
dust particles preserved in the snow of the Antarctic. According to
current estimates, about 40,000 tons of extraterrestrial matter hit the
Earth every year. "During its journey through interplanetary space, the
cosmic dust is charged with helium atoms by the solar wind. At his point
they are highly enriched with the rare helium isotope 3He," explains Dr
Hubertus Fischer, head of the research program "New keys to polar
climate archives" at the Alfred Wegener Institute. "Cosmic dust
particles in the size of a few micrometers enter the Earth's atmosphere
unharmed and carry their helium load unchanged to the Earth's surface
where they are, among other places, preserved in the snow and ice of the
polar ice caps." Due to the high temporal resolution uniquely to be
found in ice cores, it has now been possible for the first time to
determine the temporal variability of this helium flux between glacial
and interglacial periods along with the 3He and 4He ratios of these
exotic particles. The results are expected to have significant impact on
interpretation of high-resolution climate archives, such as ice, marine
and lake sediment cores.
This, however, is not all the helium isotope method has to offer. The
ratio of 4He in terrestrial dust to the dust concentration itself
reveals a marked difference between the last Ice Age and the current
warm period. As . Gisela Winckler, head of the working group "Isotope
Tracers and Constant Flux Proxies" at L-DEO says, "the terrestrial dust
coming down on Antarctica during the Ice Age obviously is not the same
as that during warm periods. This may be due to the mineral dust
originating from different regional sources or to changes in weathering,
the process responsible for production of dust." Both scientists now
want to intensify their collaboration even further and investigate the
details of this phenomenon.
EPICA
Data for this study have been collected within the European Project for
Ice Coring in Antarctica (EPICA). As the German partner within EPICA,
Alfred Wegener Institute is responsible for the Dronning Maud Land
drilling operations. The EPICA project is carried out by a consortium of
ten European countries (Belgium, Denmark, France, Germany, UK, Italy,
the Netherlands, Norway, Sweden and Switzerland). Coordinated under the
roof of the European Science Foundation (ESF), EPICA is funded by the
participating countries and the European Union.
The manuscript "30,000 Years of Cosmic Dust in Antarctic Ice" will be
published in Science on July 28, 2006.
Bremerhaven, July 27, 2006
In case of publication, please provide a copy.
Your contact person at Alfred Wegener Institue is Dr Hubertus Fischer
(0471-4831 1174; email [EMAIL PROTECTED]) and in the public
relations department. Dr Angelika Dummermuth (0471-4831 1742; email
[EMAIL PROTECTED]). For further information from LDEO, please
contact Dr Gisela Winckler (++1-845-365 8756 or
[EMAIL PROTECTED]) and for media contact: Mary Tobin (Tel.
++1-212-854 9485; email: [EMAIL PROTECTED]) or Ken Kostel (Tel.
++1-212-854 9729; email: [EMAIL PROTECTED]). Printable images can
be found on our webpage at
http://www.awi-bremerhaven.de/AWI/Presse/PM/index-d.html.
Lamont-Doherty Earth Observatory (L-DEO), member of the Earth Institute
at Columbia University, is one of the world's leading research centres
examining the planet from its core to its atmosphere, across every
continent and every ocean. From global climate change to earthquakes,
volcanoes, environmental hazards and beyond, Observatory scientists
provide the basic knowledge of Earth systems needed to inform the future
health and habitability of our planet.
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