Re: Please check my math

Russell Wallace <russell.no.spam@xxxxxxxxx> wrote:
Michael Ash wrote:
But take a major impactor and
spread it out, and even an entire hemisphere of the Earth isn't enough.

Depends entirely on which hemisphere. 100 million megatons worth of heat
dumped into the Pacific won't get you much of anything except a bit of
cloudy weather. The same amount of heat dumped into Europe could set the
whole continent on fire.

I'm not sure how vaporizing the top three feet of the entire Pacific Ocean
qualifies as "won't get you much of anything". It's going to be vastly
worse than "a bit of cloudy weather".

In most places on Earth, the temperature difference between day and night
is marked. The Sun's paltry ~20kJ/m^2 in one day is enough to raise the
temperature by 10C or more.

The hypothetical Chicxulub replay I worked with would release one hundred
thousand times that much energy.

I think the clouds you discuss will be made of live steam. Survival will
be largely due to luck, and will be extremely rare.

Even if we assume that it neatly toasts the entire hempisphere (which,
btw, will include about half each of Australia and the US on the edges,
from what I can see using Google Earth) and ignores the other half for the
most part, that heat isn't going to stay confined. How much will global
temperatures rise? It surely won't take long to circulate to the other
half of the earth, and while it's going to be radiating away into space
all this time and cooling, I suspect that radiation will proceed slower
than heat transfer to the other hemisphere.

Can anyone with a better background in these topics make a guess at just
how much the global temperature would rise before it peaked and the globe
started to cool?

In practice you won't make gravel of the whole thing without applying
enough of a blast that most of the gravel cloud misses. A more probable
scenario is that you get chunks in a range of sizes. In the event of a
land impact, that mightn't be a win; it might very well even be a net
loss. In the event of an ocean impact it's a big win, because more of
the energy goes into heating water rather than raising a tsunami,
punching through to the ocean floor etc.

"More of the energy goes into heating the water" means you create
approximately 220,000 cubic kilometers of live steam if the water is
heated just enough to vaporize it. This is the same amount as in the
hemisphere scenario, of course, but more concentrated. It shouldn't be
hard to see why having it all originate in a single place is better than
covering half the globe with it, but it's still going to be much worse
than putting that energy into tsunami or breaking and heating rock. I
assume a single large impactor crashing through the ocean and hitting the
ocean floor is mostly going to heat the rock. This will eventually go into
the water but it will be more gradual. The slower the heat is released the
less global impact you'll have in the end.

Land impacts prefer single impactors as well, at this size. Here your
choice is setting the entire continent on fire and drastically heating the
rest of the planet if your particles are small enough to burn up in the
atmosphere, leveling much of the continent and heating the atmosphere a
great deal but over a longer period of time if you have gravel but it's
large enough to reach the ground, or a crater some hundreds of kilometers
across, with the heat presumably being released slowly.

--
Michael Ash
Rogue Amoeba Software
.

Relevant Pages

  • Re: Earths Temperature
    ... to radioactive decay in the earth. ... The heating from the Sun is negligible here - it only heats up the ... And the incoming heat from the Sun ...
    (sci.astro.amateur)
  • Re: heat corpuscles in the mantle
    ... >> me, ..and he's very keen on convection in the mantle and subduction, as ... >> way, ..and if that is so, then the Earth is getting bigger, and the ... >> corpuscles of heat tied up in minerals which are locked in the solid ... >> drive convection in water, why would it drive it in solid rock? ...
    (sci.geo.geology)
  • Re: heat corpuscles in the mantle
    ... >> me, ..and he's very keen on convection in the mantle and subduction, as ... >> way, ..and if that is so, then the Earth is getting bigger, and the ... >> corpuscles of heat tied up in minerals which are locked in the solid ... >> drive convection in water, why would it drive it in solid rock? ...
    (sci.geo.geology)
  • Re: heat corpuscles in the mantle
    ... > me, ..and he's very keen on convection in the mantle and subduction, as ... > way, ..and if that is so, then the Earth is getting bigger, and the ... > The question was:- In a mantle that is convecting because of the heat ... > drive convection in water, why would it drive it in solid rock? ...
    (sci.geo.geology)
  • Re: Kook warning, Oriel36
    ... elliptical orbit,in accordance with Kepler's second law,the Earth ... perihelion motion is more pronounced hence Southern hemisphere summers ... heliocentric orbital motion but it may be just too complex for you,but ...
    (sci.geo.geology)
Loading