Amount of damage from impacts

[RedFox]

What areas of the oceans would there be the least damage to Earth's ecosystems if there was an asteroid or comet impact there? What areas of land would have the least damage upon impact? What about shorelines?
I think that damage would be minimized for an ocean impact if the object hit the Arctic ocean because there's not much to kill there. For a land impact, I'd guess that it'd be the interior of Antarctica. For an impact on a shoreline, I guess that it'd be on an Arctic shore because any tsunami created would be contained within the Arctic unlike in the Antarctic region.
What minerals would result in more damage if an impact hit them? I think I read somewhere that sulfur and salt deposits at the KT impact made it worse than those in regions without those minerals like the impact in the Canadian shield.

[JoeP]

Interesting q. Are you writing a novel, or are you planning to destroy the earth? :drevil:

I'm pretty sure the damage caused by an impact of anything much bigger than the 1908 Tunguska event is not localised. Something hitting the arctic or antarctic would cause global changes in sea levels and weather (and probably ocean currents) due to melting of ice. And the tsunami from an arctic impact would be orders of magnitude bigger than the Indian ocean earthquake; it would definitely* circle the globe.

An impact in the Sahara ... global dust clouds? In the rainforests ... loss of carbon fixing and global warming?

For some reason I think an impact in high altitude areas like the Himalayas would be more confined.

* Definitely: on a scale of "I know nothing about this" to "I know nothing about this"

[JoeP]

btw, nice colour avatar :thumbup:

[CARLA]

:hide: Your scaring me. If you answer JoeP question : I might gain some insight. I don't care which one hits, the damage would be extensive, and golbal in its devastation. Do you have a feeling about this happening ??

Are you writing a novel, or are you planning to destroy the earth? :eek:

* Definitely: on a scale of "I know nothing about this" to "I know nothing about this" :eek:

[The Lone Ranger]

Hmm. Well, the Arctic Ocean and the Antarctic regions of the world's oceans are two of the most productive ecosystems on the planet, because of upwellings that bring nutrients from the deep ocean close to the surface there. The Arctic and Antarctic oceans contain ecosystems that are much more productive than ecosystems almost anywhere in the deep temperate-zone or tropical oceans. A big impact in either ocean region would therefore have tremendous repercussions for marine ecosystems.

On the other hand, the Arctic Ocean is almost entirely surrounded by land, so an impact there would mean that any resulting tsunamis would impact lands that are almost entirely devoid of human presence. That's good, I guess. Such wouldn't be the case for an impact in the Antarctic region.

As RedFox points out, an impact on the shore of the Arctic Ocean would have the "advantage" that the resulting tsunamis would be mostly contained within the Arctic Basin. Any hit on a shoreline or on land (or a shallow-enough ocean basin, which is a problem with the Arctic Ocean, since it's relatively shallow everywhere) brings in the additional complication that you'll have millions of tons of pulverized rock and soil thrown into the atmosphere, which will reduce the amount of sunlight reaching the Earth's surface. Plus, you'll have a fireball, which would incinerate everything nearby, and start forest fires perhaps as far as hundreds of miles from the impact site.


Probably the "best" place for a water impact would be the middle of the Pacific, as far from any major landmasses as possible. There would be tsunamis to be sure, but there would be no fireball to speak of, and there would be relatively little dust and rock thrown up into the atmosphere (lots of water vapor though) -- unless it were a truly massive impact, capable of punching right through the ocean and vaporizing not just a few miles of water but some of the underlying oceanic basin as well. In that case, it doesn't much matter where it hits.


I'm inclined to agree that the "best" place for a land impact would be the middle of the Antarctic continent.

I'm not sure that the mineral composition of the impact site matters all that much. If it does, I'd imagine that someplace with a deep granitic layer (like the aforementioned Canadian Shield) would be a "better" place for an impact than someplace with less-dense rock. You probably wouldn't want an impact to occur right at the boundary between two continental plates, for obvious reasons.


Cheers,

Michael

[RedFox]

The KT impact site was rich in sulfur salts and they say that may have formed into sulfur dioxide when thrown up and into sulfuric acid when in the atmosphere. It'd block sunlight when in the stratosphere and make acid rain once in the troposphere. The impactor could bring in its own sulfur too.
The impact may have released methane from the ocean bottom that fueled fires that added to the particles blocking sunlight. The fires may have been started by radiant heat from the reentering material. If any significant amounts of methane did get released, it could be fuel.

http://www.lpl.arizona.edu/SIC/impact_cratering/Enviropages/atmossulphur/sulphurweb.html
http://www.space.com/scienceastronomy/astronomy/dinosaurs_fry_991118.html
http://news.nationalgeographic.com/news/2002/02/0222_020222_dinodust.html
http://www.google.com/search?hl=en&lr=&safe=on&c2coff=1&client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&q=sulfur+impact+asteroid&btnG=Search

Was the KT impact one of the worst that could have happened to the Mesozoic world?

Thanks for the comments on impact sites. I thought of this when playing with the impact effects program here http://www.lpl.arizona.edu/impacteffects/

[The Lone Ranger]

The KT impact site was rich in sulfur salts and they say that may have formed into sulfur dioxide when thrown up and into sulfuric acid when in the atmosphere. It'd block sunlight when in the stratosphere and make acid rain once in the troposphere. The impactor could bring in its own sulfur too.

Last I heard, there's nowhere near as much consensus among paleontologists and geologists that the Chicxulub impact site represents the "coup de grace" against the dinosaurs as is generally believed. In any event, a major impact on sulfur-rich soil/rocks would indeed create a significant acid-raid event afterward. On the other hand, any major hit on or near land would do so, because of all the nitrogen oxides that would be created in the fireball, causing acid rain on a planetary scale.

The impact may have released methane from the ocean bottom that fueled fires that added to the particles blocking sunlight. The fires may have been started by radiant heat from the reentering material. If any significant amounts of methane did get released, it could be fuel.
The hit would have to be on or very near a shoreline for this to be significant, I'd think. (Methane released at the impact site would make for a bigger fireball if the strike is on land or in sufficiently shallow water -- there won't be a fireball if the impact is in deep water, unless it's a really big impact, in which case methane's the least of your worries.) If the asteroid hits deep water, any methane released is going into the atmosphere, but it's hardly likely that so much will be released that it's going to be fuel for fires -- it's not like the atmosphere is suddenly going to become 10% (or even 1%) methane, after all. The real concern here (I would imagine) is that methane is a potent greenhouse gas.

Was the KT impact one of the worst that could have happened to the Mesozoic world?
Well, I imagine that a hit in shallow water near shore would be the worst of both worlds: you'd get tsumanis from the water hit, plus a fireball, lots of pulverized rock thrown into the atmosphere, and ensuing forest fires. In addition, there will be pieces of planetary crust launched into temporary orbits that'll rain down afterwards, creating even more impact events. All in all, a bad scenario.

Cheers,

Michael