Impact Craters on Earth

There are some fascinating pics of impact craters on earth at this
site.
www.lpi.usra.edu
They are all from Australia, Africa and Canada it seems. Are there any
in Europe or Asia? Farming can't have wiped out *all* of the old
craters. I'm still looking for a complete list and pics

steppenvalve wrote:
There are some fascinating pics of impact craters on earth at this
site.
www.lpi.usra.edu
They are all from Australia, Africa and Canada it seems. Are there
any
in Europe or Asia? Farming can't have wiped out *all* of the old
craters. I'm still looking for a complete list and pics.

Just took another look at this site. Maybe it's the best database there
is. Some of the desert craters look positively martian. Could be a
great place to film a science fiction movie.

But I still wonder why there seem to be no craters in Italy, Spain,
Japan, only one in France, a few in Germany, etc. Don't see any in
China or India, either. How much does politics have to do with this?
Russia has a bunch they've discovered.

On 2004-07-26, steppenvalve wrote:
steppenvalve wrote:
There are some fascinating pics of impact craters on earth at this
site.
www.lpi.usra.edu
They are all from Australia, Africa and Canada it seems. Are there
any
in Europe or Asia? Farming can't have wiped out *all* of the old
craters. I'm still looking for a complete list and pics.

Just took another look at this site. Maybe it's the best database there
is. Some of the desert craters look positively martian. Could be a
great place to film a science fiction movie.

But I still wonder why there seem to be no craters in Italy, Spain,
Japan, only one in France, a few in Germany, etc. Don't see any in
China or India, either. How much does politics have to do with this?
Russia has a bunch they've discovered.

I suspect it's a density thing.

Europe, China and India have historically had large farming populations,
significantly more so than in most of Africa or central Asia, and
certainly more than in most of the Americas and Australia.

Human populations tend to change the landscape around them subtly, but
more importantly they change the way you view the landscape - in fact, I
live in a remarkable example of this. Edinburgh has been said, stealing
from some obsure South European city g, to have been built on seven
hills. It's surprisingly hard to figure out where these are unless you
have a list... because they don't really seem like "hills", like
identifiable geographic features, they're more landscape.

If you have a large crater in Germany, with a sharp raised edge, and an
identical one in Arizona - that German one will probably contain a town,
there'll be roads running over it, a village here and there, some
forestry, lots of patchwork farming... and the Arizona one will be
sitting in the desert. Couple this with the fact that Central Europe
will likely get a lot more weathering than Arizona does, and the Arizona
one is likely to be more apparent.

Now, throw in the way these get found. Until recently, it was
essentially by someone going out and noticing a large crater. Settled
areas get surveyed, but they don't get mapped from scratch; if you're
re-surveying Saxony, you don't expect to suddenly discover a hitherto
unrealised feature, one that isn't apparent until you look at a map and
make a leap of judgement. And, so, you often don't.

It should also be noted that a crater on a floodplain in a temperate
climate may well end up getting glaciated, which would be likely to
really reduce your chance of identifying it. (I'm not a geologist;
anyone?)

Summary: You find lots of craters in large, flat, sparsely populated
areas because:

1) there isn't a population there to obscure matters
2) they're more likely to hit large areas
3) they're less likely to get weathered away in a desert than in a
floodplain, and more obvious on flat land than in hills.

Thoughts?

--
-Andrew Gray

Andrew Gray wrote:
On 2004-07-26, steppenvalve wrote:

www.lpi.usra.edu

(snip my own babble)


I suspect it's a density thing.

Europe, China and India have historically had large farming
populations,
significantly more so than in most of Africa or central Asia, and
certainly more than in most of the Americas and Australia.

Human populations tend to change the landscape around them subtly,
but
more importantly they change the way you view the landscape - in
fact, I
live in a remarkable example of this. Edinburgh has been said,
stealing
from some obsure South European city g, to have been built on seven

hills. It's surprisingly hard to figure out where these are unless
you
have a list... because they don't really seem like "hills", like
identifiable geographic features, they're more landscape.

If you have a large crater in Germany, with a sharp raised edge, and
an
identical one in Arizona - that German one will probably contain a
town,
there'll be roads running over it, a village here and there, some
forestry, lots of patchwork farming... and the Arizona one will be
sitting in the desert. Couple this with the fact that Central Europe
will likely get a lot more weathering than Arizona does, and the
Arizona
one is likely to be more apparent.

Now, throw in the way these get found. Until recently, it was
essentially by someone going out and noticing a large crater. Settled

areas get surveyed, but they don't get mapped from scratch; if you're

re-surveying Saxony, you don't expect to suddenly discover a hitherto
unrealised feature, one that isn't apparent until you look at a map
and
make a leap of judgement. And, so, you often don't.

It should also be noted that a crater on a floodplain in a temperate
climate may well end up getting glaciated, which would be likely to
really reduce your chance of identifying it. (I'm not a geologist;
anyone?)

Summary: You find lots of craters in large, flat, sparsely populated
areas because:

1) there isn't a population there to obscure matters
2) they're more likely to hit large areas
3) they're less likely to get weathered away in a desert than in a
floodplain, and more obvious on flat land than in hills.

Thoughts?

--
-Andrew Gray


I posted this same link, with sort of the same question, on another
newsgroup[1] and got a different supposition. The poster suggested that
Canada and Australia have a lot because they are goelogically stable.
I don't know how long Canada has been frozen tundra (some of their
craters are half a billion years old) but Australia appears to get few,
I don't know, earthquakes? A lot of the craters have been recently
discovered by flying planes over the land and mapping the magnettic
field. They see a ring on their map, go back and look at the ground
(with a landsat sometimes) and are able to discerne a faint ring etched
into the ground.

Steppenvalve

[1] A delightful breakfast-oriented group with an English flair, though
there are some Yanks, called
"alt.2eggs.sausage.beans.tomatoes.2toast.largetea. cheerslove".

Most craters are where bedrock is oldest. Most areas in Europe are only some
hudreds of million years old, about one tenth of the age of earth and other
planets. So the probability to find many craters is low. Most of bedrock in
Finland is 1600 - 2000 millions of years old. So 10 major craters have been
found here untill now. There are similar old rock areas on other continents
as well in Canada and Australia for instance.

Antti Järvi
Espoo Finland




"Andrew Gray" kirjoitti viestissä
. ..
On 2004-07-26, steppenvalve wrote:
steppenvalve wrote:
There are some fascinating pics of impact craters on earth at this
site.
www.lpi.usra.edu
They are all from Australia, Africa and Canada it seems. Are there
any
in Europe or Asia? Farming can't have wiped out *all* of the old
craters. I'm still looking for a complete list and pics.

Just took another look at this site. Maybe it's the best database there
is. Some of the desert craters look positively martian. Could be a
great place to film a science fiction movie.

But I still wonder why there seem to be no craters in Italy, Spain,
Japan, only one in France, a few in Germany, etc. Don't see any in
China or India, either. How much does politics have to do with this?
Russia has a bunch they've discovered.

I suspect it's a density thing.

Europe, China and India have historically had large farming populations,
significantly more so than in most of Africa or central Asia, and
certainly more than in most of the Americas and Australia.

Human populations tend to change the landscape around them subtly, but
more importantly they change the way you view the landscape - in fact, I
live in a remarkable example of this. Edinburgh has been said, stealing
from some obsure South European city g, to have been built on seven
hills. It's surprisingly hard to figure out where these are unless you
have a list... because they don't really seem like "hills", like
identifiable geographic features, they're more landscape.

If you have a large crater in Germany, with a sharp raised edge, and an
identical one in Arizona - that German one will probably contain a town,
there'll be roads running over it, a village here and there, some
forestry, lots of patchwork farming... and the Arizona one will be
sitting in the desert. Couple this with the fact that Central Europe
will likely get a lot more weathering than Arizona does, and the Arizona
one is likely to be more apparent.

Now, throw in the way these get found. Until recently, it was
essentially by someone going out and noticing a large crater. Settled
areas get surveyed, but they don't get mapped from scratch; if you're
re-surveying Saxony, you don't expect to suddenly discover a hitherto
unrealised feature, one that isn't apparent until you look at a map and
make a leap of judgement. And, so, you often don't.

It should also be noted that a crater on a floodplain in a temperate
climate may well end up getting glaciated, which would be likely to
really reduce your chance of identifying it. (I'm not a geologist;
anyone?)

Summary: You find lots of craters in large, flat, sparsely populated
areas because:

1) there isn't a population there to obscure matters
2) they're more likely to hit large areas
3) they're less likely to get weathered away in a desert than in a
floodplain, and more obvious on flat land than in hills.

Thoughts?

--
-Andrew Gray