by Michael Paine (mpaine AT
Updated 27 May 2004. Caution: Many items are speculative at this stage.
This table is associated with my article "Source of the Australasian Tektites?" that appeared in the February 2001 issue of Meteorite (no longer online). PDF preprint (300K). See also the Bioastronomy 2002 paper by Michael Paine and Benny Peiser: The Frequency and Consequences of Cosmic Impacts Since the Demise of the Dinosaurs (280K PDF).
There are many environmental effects from the impact of a large asteroid or comet (diameter 1 kilometre or more) with the Earth. These effects depend mainly on:
For the effects of smaller impactors see Tsunami
from Asteroid Impacts. For some of the consequences of impacts see Impacts
I have not had a chance to check these values against the new (9 Apr 04) calculator available at the University of Arizona.
|Asteroid Diameter||1 km (1000 yards)||2 km (1.2 miles)||5 km (3 miles)||10 km (6 miles)|
|Kinetic Energy (millions of megatons of TNT)||0.1||1||10||100|
|Average impact interval (years)||200,000||500,000||10 million||100 million|
|Crater Diameter - rim to rim and [transient]||24 km
|Radius for ignition from fireball radiation (within seconds)||150 km||250 km||600 km (but see ballistic ejecta)||1800 km (but see ballistic ejecta)|
|Blast radius for
4psi overpressure (500km/h winds,
Also bombardment by debris
[1 psi overpressure] (trees knocked over, glass windows shatter)
|Dust and debris fallout cover the ground and cause severe mud flows. (months)||300 km||400 km||1100 km||4000 km|
|Area for firestorm ignition due to radiation from ballistic reentry of ejecta (within hours)||Local||Local
(600 km radius)
(5000 km radius)
|Earthquakes, hurricanes and tsunami (hours to months)||Regional||Regional||Global||Global|
|Dark skies and cooling from dust, soot and oxides of sulfur.||Regional freezing for weeks. Moderate global effects for weeks (equivalent to Tambora volcanic explosion).||Skies darker than darkest cloud cover.
Global drop of 8C for weeks then moderate global effects for months (no summer).
|Severe global effects, day becomes night for months.||Very severe global effects. Day becomes night for months. Freezing conditions away from coastlines.(KT event "winter" lasted around 3 years)|
|Acid Rain, pyrotoxins (poisons from fires) and heavy metals.||Regional for months||Regional for months||Global for months||Global for years
|Ozone destruction (hazard from UV radiation)||Partial global destruction for years||Severe global destruction for years||Total global destruction for years||Total global destruction for decades|
|Global Greenhouse heating from water and CO2||Negligible||Minor for years||Moderate for decades||Major for centuries|
|Global iridium layer (nanograms per square cm) - a signature of the impact.||0.4||2||8||80|
|Plant growth and extinctions.||Disrupted for months. Some global crop failures.||Disrupted for years. Some regional extinctions. Global crops failures.||Photosynthesis stops for months. Decades for plants to recover. Major regional extinctions.||Hundreds of years. Global mass extinctions|
1. Most values are very approximate - within an order of magnitude.
2. Crater diameters were derived from Jay Melosh's Crater Calculator, using dense rock impactor and target surface and a 45 degree impact angle. Two diameters are given, the transient crater formed at the instant of the explosion and the rim-to-rim crater that forms after the transient crater collapses, the ground slumps (usually in concentric rings - see Melosh 1997) and the "rim" spreads further out. The transient crater is important for calculating environmental effects since it is associated with ejected material. The rim-to-rim crater is the one that geologists should be looking for. It is possible that the Indo-China event involved a very low impact angle.
3. Fireball ignition radius and ballistic ejecta ignition radius from Toon Figure 16. See updated figures at SWRI News Release (Aug 04)
4. 4 psi Blast radius from Toon Figure 5. 1 psi blast radius based on 4 psi radius times 2.3 (average resulting from a simulation using Lewis's software). Rock projectiles are assumed to be deadly over a similar range to the 4 psi blast wave. The dust and debris fallout is assumed to affect an area which is similar to that of the 1 psi blast wave, as was apparently the case with the Mt St Helens volcanic eruption. Dust fallout and projectiles tend to be ignored in most papers on environmental effects of impacts - perhaps because they tend to be confined to regions already devastated by the blast wave. However, the fallout would severely hamper the recovery of a region - as was the case with Mt St Helens. Update May 04: The LPL calculator gives a blast radius substantially less than that shown here (about one fifth). Jay Melosh informs me that the earlier work did not account sufficiently for the limited depth of the atmosphere and the Earth's surface curvature.
5. According to Turco, atmospheric nitrous oxide created by the "small" 1908 Tunguska event probably caused the 30% depletion in the northern hemisphere ozone shield that was observed in the year following the explosion.
6. Global iridium from Gersonde. Note that there will be greater concentrations of iridium near the impact site, particularly with the smaller impacts.
7. "Earthquakes" are mostly due to premature initiation of terrestrial earthquakes as the impact shockwaves pass around the Earth's crust.
8. Another indirect consequence of impacts may be the release of huge amounts of methane (a potent Greenhouse gas) from undersea deposits of methane hydrates. See:
Ball P (2000) When it's cool to be cool , Nature Science Update 4 August 2000.
BBC (1998) Meteorite is possible ice age culprit - 3.3 million years ago but discuss impacts and climates.
Chapman C. (2001) White Paper on Impact Hazard, South West Research Institute.
Garshnek V., Morrison D. and Burkle F. (2000) 'The mitigation, management and survivability of asteroid/comet impact with Earth' J Space Policy Vol 16 (2000) 213-222 (not online)
Gersonde R., Kyte F.T., Bleil U., Diekmann B., Floress J.A., Gohl K., Grahl G., Hagen R., Kuhn G., Sierros F.J., Volker D., Abelmann A. and Bostewick J.A. (1997) 'Geological record and reconstruction of the late Pliocene impact of the Eltanin asteroid in the Southern Ocean', Nature No.390, 357-363, 27 Nov 1997. http://www.nature.com/
Gerasimov M.V. (2000) 'Production of toxins during an impact and their possible role in a biotic mass extinction', International Conference on Catastrophic Events and Mass Extinctions: Impacts and Beyond, 9-12 July 2000, Vienna, Austria, abstract no.3051.
Glass B.P. and Pizzuto J.E. (1994) 'Geographic variation in Australasian microtektite concentrations: Implications concerning the location and size of the source crater', J of Geophysical Research vol 99 no.E9, 19075-19081, Sept 1994 (abstract only)
Howard K.T., Bunopass S., Burret C.F., Haines P.W. and Norman M.D. (2000) 'The 770KA tektite producing impact event: evidence for distal environmental effects in NE Thailand', Proceedings of 31st Lunar and Planetary Science Conference, March 2000. http://www.lpi.usra.edu/meetings/lpsc2000/
Koeberl C. and B.P. Glass (2000) 'Tektites
and the Age Paradox in Mid-Pleistocene China', Science, 289,
No 5479, 28 Jul 2000, p. 507. and the response by Potts et al. http://www.sciencemag.org/
Kring D.A., Melosh H.J. and Hunten D.M (1995) 'Possible climate perturbations produced by impacting asteroids and comets', Meteoritics.
Kring D.A. and Durda D.D. (2001) 'The distribution of wildfires iginited by high-energy ejecta from the Chicxulub impact event', Proceedings of 32nd Lunar and Planetary Science Conference. March 2001.
Larick R. and Ciochon R. (1996) 'The African emergence and early asian dispersals of the Genus Homo', American Scientist, Nov-Dec 1996. http://www.amsci.org/articles/96articles/Larick.html
Lewis J.S. (1999) Comet and asteroid impact hazards on a populated Earth, Academic Press. Comes with simulation software.
O'Keefe J., Lyons J. and Ahrens T. (2000) 'Impact mechanics and implications for extinctions', International Conference on Catastrophic Events and Mass Extinctions: Impacts and Beyond, 9-12 July 2000, Vienna, Austria, abstract no.3142.
Robock Alan (2001) Volcanic eruptions and climate
Schmidt G., Zhou L and Wasson J. (1993) 'Iridium in sediments containing large abundances of Australasian microtektites from DSDP hole 758B in the Eastern Indian ocean and from DSDP hole 769A in the Sulu Sea', 24th Lunar and Planetary Science Conference (abstract only)
Turco R., Toon O., Park C., Whitten R., Pollack J. and Noerdlinger P. (1982) 'An analysis of the physical, chemical, optical and historical impacts of the 1908 Tunguska meteor fall', Icarus vol. 50 Apr 1982 1-52.
Yamei H., Potts R., Baoyin Y., Zhengtang G., Deino A., Wei W., Clark J., Guangmao X and , Weiwen H. (2000) 'Mid-Pleistocene Acheulean-like stone technology of the Bose Basin, South China', Science, vol 287 1622-1626.