Re: "NASA to study "city-killer" asteroid as odds of hitting Earth go up"

On Mon, 17 Feb 2025 18:11:03 -0000 (UTC), jdnicoll@panix.com (James
Nicoll) wrote:

In article <2hq6rjl8gsv2h80cljfoqt70pom5p58d5i@4ax.com>,
Paul S Person  <psperson@old.netcom.invalid> wrote:

On Sun, 16 Feb 2025 16:40:22 -0000 (UTC), jdnicoll@panix.com (James
Nicoll) wrote:
>

[on the Deep Impact impact]

>

wave height for an impact in deep water is roughly
>
h = 6.5m [y/gigaton] 0.54 [1000km/r]
>
h = wave height
r = range to impact
y = yield
>
Idealised wave run in (which is to say, not applicable to any real region):
>
Xmax ~ 1.0km [h/10 meters]^[4/3]
>
Impact energy in Deep Impact seems to be 500,000 MT.
>
At 1000 km, the wave would be 6.5x500x.54 or about 1800 m, which seems
kind of bad.

>
It looks /very/ impressive in the movie!
>

h/10 is 180, so Xmax is almost exactly 1000 km, which also seems bad.
Mind you, that wave is going to have a heck of a time getting past
the Appalachians so Ontario should be fine.

>
The second one, had it hit, would have hit on the Canadian Shield
(IIRC). Bing suggests that this is not Ontario, but, since this is
"the planet-killer", not actually being hit wouldn't matter much.
>
In the film, we see it go up a valley while the survivors climb the
surrounding hills. This is the bit I am using as a counter-example to
the "water lapping gently at the seashore" nonsense promoted by some.
The coastal cities, of course, are gone. I would think Labrador would
be impacted as well, but I'm sure how far north of the impact they
are.
>
I seem to recall from the bit at the end indicating that the water
reached over the Appalachians into the Ohio valley (and related areas)
before receding. The amount of water and the force with which it moved
would, of course, be constantly reducing once it hit land.
>
So, yes, Ontario (and everything West of the Mississippi for that
matter) would have escaped.

>
I wonder how having billions of tons of salt water deposited affects
soil? Aside from the obvious erosion issues, I mean.

Not well, I suspect. If it were beneficial, they'd be using salt water
for irrigation. I am referring, of course, to land that is not
normally exposed to salt water, not to some coastal regions where the
plants have adapted.

Boundary markers might also be affected. Lots of surveyors needed!

IIRC, some have theorized that geometry began in Egypt to reset the
field boundaries after each year's flooding.
--
"Here lies the Tuscan poet Aretino,
Who evil spoke of everyone but God,
Giving as his excuse, 'I never knew him.'"