Though it appears at first that these energies are hard to imagine, it is very straightforward to do the calculations.
I don't have time to rebuild the calculations I've done several times in the past now, though.
Simply assume a mass 0.5-10 miles (1000-16000 meters) on a side and with a density about 3-5 times that of water for rock, 1-1.5 times water (which is 1000 kilograms/ cubic meter) for a water laden comet. It doesn't matter that much. It is easier to assume the mass is cubic instead of roundish, and again it doesn't matter much.
The huge energy factor is the velocity, which ranges from 20,000-80,000 mph (10-40 kilometers/ sec) for most comets/meteors/asteroids when they strike the earth's atmosphere.
For ease of your calculations, I provide that a single megaton of energy is equal to 4,186,000,000,000 joules (4.186 X 10^12) of energy (1,000,000,000 kilogram-meter^2/ sec^2) ... and I suggest you convert the masses and dimensions for your impact body to metric.
You will find that a moderate size asteroid striking the earth deposits many, many times the energy of the full arsenal of nuclear bombs on earth. Even the small 1ft diameter rocks end their life as spectacular fireballs seen noted for hundreds of miles. Fortunately, we don't get hit by anything bigger than a ten or twenty yards in diameter very often, but even those result in things like Crater Lake.
I though Crater Lake was volcanic in origin.
Here's an online facsimile of a paper rejected for publication in 1968. Have times changed? Or is it like Thoreau (or somebody) said -- "Times don't change. We change." ;')A Flash From the Past:On the Moon, material that is freshly exposed has a slight bluish tinge. Over time, because of the constant bomb ardment of cosmic rays, other high-energy particles and micrometeorites, the structure of the material changes and iron particles tend to predominate, making the material slightly red.
New Evidence Supports Moon Blast
by Henry Fountain
March 4, 2003
In the Clementine photos, Dr. Buratti and Mr. Johnson found o ne small crater that was "very, very blue and fresh appearing," Dr. Buratti said. It also happened to be in the exact center of the area they were looking. And it was the proper size slightly less than a mile across, including the ejecta blanket. Dr. Bu ratti estimated the size of the asteroid at 20 yards in diameter.A Celestial CollisionEarly in the evening of June 18, 1178, a group of men near Canterbury, England, stood admiring the sliver of a new moon hanging low in the west. In terms they later described to a monk who recorded their sighting, "Suddenly a flaming torch sprang from the moon, spewing fire, hot coals and sparks." In continuing their description of the event, they reported that "The moon writhed like a wounded snake and finally took on a blackish appearance"... [P]lanetary scientist Jack Hartung of the State University of New York... gathered enough clues to suggest that a large asteroid... might have smacked into the moon just over the horizon on the back side. To test his suspicion, Hartung went to the Lunar and Planetary Institute in Houston, and inspected Russian and American photographs of the moon's back side. Sure enough, in just the right place, he found a remarkably fresh crater, 12 miles across and twice as deep as the Grand Canyon. From it radiated white splatter marks for hundreds of miles... Such an impact, reason astrophysicists, would set the moon to ringing like a gong for thousands of years... At Texas' McDonald Observatory, astronomers Odile Calame and J. Derral Mulholland of the University of Texas find that the surface of the moon moves back and forth fully 80 feet! Such an oscillation clearly implies a collision with something large, sometime within the not-too-distant past, probably within the memory of mankind. The problem is that there is no way to peg the date exactly at 1178.
by Larry Gedney
February 10, 1983Manicouagan CraterOriginally about 60 miles wide, this crater in Quebec, Canada, is one of the largest impact craters remaining on the planet. One of the distinguishing features of the more than 200 million-year-old crater is a ring lake. Popular with scientists, the crater has provided key insights about what exactly happens geologically when asteroids and comets slam into Earth.
by Dr David Whitehouse
Monday, February 15, 1999
Possible Formation of the Guatemala Basin by the Impact of an Extraterrestrial BodyThe earth must be as frequently cratered per unit area as the moon. By a relative cross section argument, more than 13 times the number of craters the size of the maria on the moon exist, or existed, on the earth. Whether such events occur with sufficient frequency in recent geologic time to provide tangible evidence today of such cratering is uncertain. From the arguments set forth, and the continuing discovery of meteorite craters on the continents (Short, 1966, Baldwin, 1963, Dietz, 1961, and Prouty, 1952) it seems likely that the importance of the effect of extraterrestrial bodies impacting the earth has been, at least, underestimated (the Alverez's hypothesis concerning the end of the dinosaurs by such a mechanism was more than a decade in the future). Certainly there is as much evidence at present to support our hypothesis for the formation of the Guatemala Basin as other hypotheses advanced to explain the low heat flow found in this basin.
by Charles E. Corry and Miller L. Bell
With the tests for shock processes advanced by Short (1966), our hypothesis should be capable of field verification or rejection.
George W. Bush will be reelected by a margin of at least ten per cent