Verschuur 95 (Gerrit L. Verschuur is a PHD in Radio Astronomy, author of Impact! The Threat of Comets and Asteroids “Impact Hazards: Truth and Consequences,” Sky & Telescope, June 1998, Vol. 95 Issue 6. EBSCO. TDA.)
The horrors deeply traumatized survivors might witness include the broiling of creatures within eyesight of the atmospheric fireball, the widespread triggering of conflagrations as fiery debris originally blasted into space plummets back to Earth, the darkening of the skies by soot and dust plunging the world into "winter" lasting months, the removal of the ozone layer, the formation of poisonous nitrogen oxides that would create corrosive acid rain, and subsequent global warming years later courtesy carbon dioxide released by vaporized rock. Furthermore, the seismic shock of impact would devastate a large area and earthquake-prone regions could release additional pent-up energy in the Earth's crust. Alain Maury, a dedicated asteroid hunter in France, has pondered further effects. "Even without an impact winter," he says, "after the initial fatalities, our banking system goes berserk, all multinational companies -- many of them dealing with food distribution -- do the same, and we do not find our cereal in our supermarket anymore." Michael Baillie (Queen's University, Belfast) believes that modern civilization would collapse after the impact of a 500-meter-wide object. "The trouble is" he says, "that a significantly smaller impact could still do the trick, especially if over an ocean. ... Civilization is a thin veneer. Take away all air travel, restrict global food supplies, demonstrate that the military and governments are ineffective, demonstrate that coastal zones should be avoided, and where would we all be? That is not to mention the problems when all the dead sea life washes up" Alas such scary words, and even evidence from dramatic computer prognostications, tend to be ignored. The most well-known recent impact event occurred in the middle of Siberia in 1908. But even Tunguska's 2,000-square-km area of flattened trees only reinforces the sense of unreality we feel toward the threat. We tend to think that the next one will also that somewhere else, not where we are. Perhaps the best thing that could happen us to the potential danger would be for a minor impact to do enough damage to frighten us into action. More specifically, as Jonathan Shanklin (British Antarctic Survey) notes, "Even a small impact on a politically significant site might be sufficient to institute a major change of direction for our present civilization" The physical consequences of even a small impact will depend crucially on where the object strikes. A hit on a major city such as Washington, D.C., or New York would cause additional political and financial ripples. Should one strike near a nuclear power station, the radiation hazard created by the release of radioactive material from an incinerated reactor might be felt worldwide. But no matter the scale of the catastrophe, the damage to our view of ourselves in the cosmic context will suffer profound trauma. As Baillie hinted, the scenario of an ocean impact is drawing great scientific interest lately. Jack G. Hills and Charles Mader (Los Alamos National Laboratory) estimate that a 5-km-wide asteroid striking the middle of the Atlantic Ocean would produce a tsunami that would swamp the entire upper East Coast of the United States back to the Appalachian Mountains. Delaware, Maryland, and Virginia would be inundated, as well as Long Island and all other coastal cities. It would also drown much of France and Portugal. According to Vitaly Adushkin and Ivan Nemchinov, two Russian scientists involved in modeling explosive events, a small-to-medium 200-meter object smashing into a 5-km-deep ocean at 50 km per second would raise a splash 35 km high in 40 seconds. It staggers the imagination to conceive of such a large curtain of water and debris. Owen Toon (NASA/Ames Research Center) and his colleagues calculate that a 10,000-megaton impact (by a 1-km object) in a 4-km-deep ocean would create devastating tsunamis over an area the size of the Pacific Ocean. Even a mere 5-megaton impact by a very small object in the ocean would generate tsunamis comparable to those produced by the largest earthquakes.
Asteroid Impact Ozone Depletion/UV radiation
Asteroids destroy the atmosphere regardless of where they hit
Courtland 10 (Rachel Courtland is a space and astronomy writer for the New Scientist. “Ocean asteroid hits will create huge ozone holes” New Scientist, October 13 2010, http://www.newscientist.com/article/dn19579-ocean-asteroid-hits-will-create-huge-ozone-holes.html, TDA)
To get a sense of how much water might be jettisoned into the atmosphere if these asteroids hit the ocean, the team modelled what would happen if they reached Earth's atmosphere at a clip of 18 kilometres per second, an average speed expected for a near-Earth object, and hit the ocean in the northern hemisphere at a 45-degree angle. As expected, the simulations showed that the larger, 1-km asteroid created the bigger splash, throwing 42 trillion kilograms of water and vapour – enough to fill 16 million Olympic-sized swimming pools – across an area more than 1000 kilometres wide and up to hundreds of kilometres above the Earth's surface. Once in the atmosphere, the water, together with compounds containing chlorine and bromine from vaporised sea salts, destroyed ozone above the Earth's atmosphere at a much faster rate than it is naturally created. Some simulated impacts created depletions that were still felt across the whole Earth a year later. "It will produce an ozone hole that will engulf the entire Earth," Pierazzo says. The longest lasting and most severe depletion – a cut of more than 70 per cent in ozone levels – occurred over much of the northern hemisphere. That's a far bigger hole than the one that was above the South Pole in 1993, when Earth's ozone layer was at its thinnest. The resulting ultraviolet-radiation levels would be higher than anywhere on Earth today, the team writes, presenting a new hazard for human civilisation. While people may be able to protect themselves from the increased threat of sunburn, the intense UV light could also affect our food supply by damaging plants and the phytoplankton that represent the bottom of the ocean's food chain. "That is enough to really cause problems for our civilisation," Pierazzo says. Better understanding these effects could help us prepare in the event of an impact. For example people could plant crops more resistant to UV radiation, she adds. Toon notes that impacts on land or shallow water may ultimately do more damage by kicking up dust that could significantly darken skies and inhibit plant growth. Pierazzo is now working on a model to assess how asteroids that hit dry land would affect the atmosphere.
An asteroid impact in the ocean would destroy the atmosphere and expose society to deadly UV radiation.
Liverpool Daily Post in 2010 (Newspaper, Liverpool Daily Post, Asteroid fear; weird world, October 27, 2010, LexisNexis, znf)
A MEDIUM-sized asteroid plunging into the ocean would destroy much of the ozone layer, leaving the Earth exposed to dangerous levels of ultraviolet radiation, it has been claimed. The impact from a space rock 500m to 1km in diameter would send vast amounts of sea water into the atmosphere where chemicals such as chloride and bromide would strip away significant amounts of ozone which provides a shield against harmful sun rays, according to US expert Dr Elisabetta Pierazzo. The result would be a huge spike in ultraviolet (UV) radiation levels with fair skins burning after just a few minutes of sun exposure, she said in the journal Earth and Planetary Science Letters.