Mathematics – Logic
Scientific paper
Dec 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agufm.u51a..10z&link_type=abstract
American Geophysical Union, Fall Meeting 2001, abstract #U51A-10
Mathematics
Logic
1630 Impact Phenomena, 5407 Atmospheres: Evolution, 5455 Origin And Evolution, 9699 General Or Miscellaneous
Scientific paper
It is more useful to define the Hadean Eon as the time when impacts ruled the Earth than to define it as the time before the rock record. For decades now it has been obvious that the coincidence between the timing of the end of the lunar late bombardment and the appearance of a rock record on Earth is probably not just a coincidence. I doubt I am pointing out something that the reader hasn't long ago given thought to. While the Moon was struck by tens of basin-forming impactors (100 km objects making ~1000 km craters), the Earth was struck by hundreds of similar objects, and by tens of objects much larger still. The largest would have been big enough to evaporate the oceans, and the ejecta massive enough to envelope the Earth in 100 m of rock rain. Smaller impacts were also more frequent. On average, a Chicxulub fell every 105 years. When one imagines the Hadean one imagines it with craters and volcanos: crater oceans and crater lakes, a scene of mountain rings and island arcs and red lava falling into a steaming sea under an ash-laden sky. I don't know about the volcanos, but the picture of abundant impact craters makes good sense --the big ones, at least, which feature several kilometers of relief, are not likely to have eroded away on timescales of less than ten million years, and so there were always several of these to be seen at any time in various states of decay. The oceans would have been filled with typically hundreds of meters of weathered ejecta, most of which was ultimately subducted but taking with them whatever they reacted with at the time --CO2 was especially vulnerable to this sort of scouring. The climate, under a faint sun and with little CO2 to warm it, may have been in the median extremely cold, barring the intervention of biogenic greenhouse gases (such as methane), with on occasion the cold broken by brief (10s to 1000s of years) episodes of exreme heat and steam following the larger impacts. In sum, the age of impacts seems sufficiently unlike the more familiar Archaean that came after that it seems useful to give this time its own name, a name we already have, and that, if applied to the Hadean that I have described, actually has some geological value.
No associations
LandOfFree
The Hadean Atmosphere does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The Hadean Atmosphere, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Hadean Atmosphere will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1240125