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Science Forum Index » Astro - Amateur Forum » Posibble old Asteroide impact on earth with 1000km...
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| chillax... |
 Posted: Tue May 06, 2008 10:01 pm |
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Open google earth on following coorinates "South Sandwich Islands" and
zoom out to 6000 km:
58° 7'28.20"S
26°13'7.85"W
You can see a big under water crater, and you see an impact path how
the
crater was created, the impact begins on the South pole "SAWB BASE
MARAMBIO" and on
the bottom of South American's "Falkland Islands / Malwinen".
It seems that south pole and south america was 1 continent which were
hit by a asteroide of a diameter of 1000 km and than splitted the
continent!
What do you think how this rock mass was created ? |
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| Chris L Peterson... |
| Posted: Wed May 07, 2008 9:00 am |
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On Wed, 7 May 2008 01:01:20 -0700 (PDT), chillax <ro.do at (no spam) gmx.de> wrote:
Quote: It seems that south pole and south america was 1 continent which were
hit by a asteroide of a diameter of 1000 km and than splitted the
continent!
No, that's not the cause of the structure you see. Between the large
South American Plate, and the large Antarctic Plate, you have the Scotia
Plate. The South Sandwich Islands are a typical volcanic island arc
lying over a subduction zone between the plates.
BTW, a collision with a 1000 km diameter object would result in the
destruction of virtually all life on Earth. Such an event, if it has
ever occurred, would have been billions of years ago, and no obvious
visible evidence would remain. The area around the Scotia Plate is very
active geologically; a smaller impact in that area would become
invisible in just a few million years.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com |
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| jerry warner... |
| Posted: Thu May 08, 2008 12:07 am |
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chillax wrote:
Quote: Open google earth on following coorinates "South Sandwich Islands" and
zoom out to 6000 km:
58° 7'28.20"S
26°13'7.85"W
You can see a big under water crater, and you see an impact path how
the
crater was created, the impact begins on the South pole "SAWB BASE
MARAMBIO" and on
the bottom of South American's "Falkland Islands / Malwinen".
It seems that south pole and south america was 1 continent which were
hit by a asteroide of a diameter of 1000 km and than splitted the
continent!
What do you think how this rock mass was created ?
By a massive outgrowth of asparagus! |
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| Margo Schulter... |
| Posted: Mon May 19, 2008 10:34 am |
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Chris L Peterson <clp at (no spam) alumni.caltech.edu> wrote:
Quote: BTW, a collision with a 1000 km diameter object would result in the
destruction of virtually all life on Earth. Such an event, if it has
ever occurred, would have been billions of years ago, and no obvious
visible evidence would remain. The area around the Scotia Plate is very
active geologically; a smaller impact in that area would become
invisible in just a few million years.
Hi, Chris.
Just to share my own immediate if a bit more amateurish agreement: this
would be an impact involving a body approximately the size of 1 Ceres,
a "dwarf planet" according to IAU terminology, or a small "macroplanet"
as I like to say (large enough to attain hydrostatic equilibrium, i.e.
collapse by self-gravity into a near-spherical or "globose" shape).
The one event on this scale, or rather larger, that I can think of is
that postulated in the Theia scenario for the origins of our Moon, where
we have the Earth sharing its orbit with another planet about the size
of Mars in 1:1 resonance, a bit like Jupiter and the Trojan asteroids.
Then things get destablized, and there's a sort of collision -- at a
shallow angle, according to one version I've seen. The name "Theia" is
appropriately that of a Titan who, in a Greek creation story, gave birth
to the Moon.
I guess that this would have been fairly soon after the formation of the
Solar System -- say 4.5 Ga (i.e. in geospeak, 4.5 gigayears ago). An
interesting point is that while Theia was in a stable 1:1 resonance with
Earth, we could call Earth a "dominant macroplanet," or IAU "planet,"
which means that the Earth had attained hydrostatic equilibrium, and had
a dramatically greater mass than all objects in the neighborhood of its
orbit _not under its gravitational control or influence_. However, when
Theia got out of a stable resonance, making a collision possible, Earth
might temporarily become a "belt macroplanet" or IAU "dwarf planet" --
massive enough for hydrostatic equilibrium, but no longer having "cleared
the neighborhood of its orbit," because Theia would be there and out of
Earth's control! Then we have the collision -- with part of Theia getting
assimilated by the Earth, and most of the rest becoming the Moon -- a
satellite, and thus again under control, so that the Earth has "cleared
the neighborhood of its orbit."
A nicety: I guess that if one thinks in terms of Earth's _ability_ to
clear its orbit within a reasonable time, then one could argue that it
remained a dominant planet (or IAU planet) even during the time when
Theia was loose, since we know that when the collision happens, Earth
is in an orbital situation where it's going to "clear its neighborhood."
Then came the Late Heavy Bombardment (ca. 4.2-3.8 Ga, as I recall), with
lots of impacts -- I wonder if there's any hypothesis as to how big the
largest impactors might have been in that era. Sometimes this era is
described as a "rain of planetesimals," which might suggest to me sizes
of around 1-100 km, plus lots of smaller objects also. An interesting
question is whether this may have interrupted the early origins of life,
or helped out the process by bringing in more organic materials. Some
paleobiologists have suggested possible evidence for "chemical fossils"
in the Isua greenbelt rocks (about 3.8 Ga), while there is widespread
acceptance of microfossils around 3.5 Ga -- although not always a
consensus about which examples from this epoch are the most convincing.
Anyway, the K-T or Cretaceous-Tertiary event of 63 Ma (megayears or
millions of years) ago has been hypothesized to have involved an impactor
of around 10km -- two orders of magnitude less than 1000km!
With many thanks,
Margo |
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