A Hole in the Atmosphere

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“Obviously, something […] big hitting the Earth is going to hit with a lot of energy. […] This is the energy one million tons of dynamite would release if it was exploded and is the energy unit used for nuclear explosions. The largest yield of a thermonuclear warhead is around 50–100 megatons. The kinetic energy of the falling object is converted to the explosion when it hits. The 10-kilometer object produces an explosion of 6 × 107 megatons of TNT (equivalent to an earthquake of magnitude 12.4 on the Richter scale). The 1-kilometer object produces a milder explosion of “only” 6 × 104 megatons (equivalent to an earthquake of magnitude 9.4 on the Richter scale).

“On its way to the impact, the asteroid pushes aside the air in front of it creating a hole in the atmosphere. The atmosphere above the impact site is removed for several tens of seconds. Before the surrounding air can rush back in to fill the gap, material from the impact: vaporized asteroid, crustal material, and ocean water (if it lands in the ocean), escapes through the hole and follows a ballistic flight back down. Within two minutes after impact, about 105 cubic kilometers of ejecta (1013 tons) is lofted to about 100 kilometers. If the asteroid hits the ocean, the surrounding water returning over the the hot crater floor is vaporized (a large enough impact will break through to the hot lithosphere and maybe the even hotter asthenosphere), sending more water vapor into the air as well as causing huge steam explosions that greatly compound the effect of the initial impact explosion.

“There will be a crater regardless of where it lands. The diameter of the crater in kilometers is = 0.765 × (energy of impact in megatons TNT). Plugging in the typical impact values, you get a 150-kilometer diameter crater for the 10-kilometer asteroid and a 20-kilometer diameter crater for the 1-kilometer asteroid. The initial blast would also produce shifting of the crust along fault lines.

The oceans cover about 75% of the Earth’s surface, so it is likely the asteroid will hit an ocean. The amount of water in the ocean is nowhere near large enough to “cushion” the asteroid. The asteroid will push the water aside and hit the ocean floor to create a large crater. The water pushed aside will form a huge tidal wave, a tsunami. […] What this means is that a 10-km asteroid hitting any deep point in the Pacific (the largest ocean) produces a megatsunami along the entire Pacific Rim.

“Some values for the height of the tsunami at different distances from the impact site are given in the following table. The heights are given for the two typical asteroids, a 10-kilometer and a 1-kilometer asteroid.

Distance (in km) 10 km asteroid 1 km asteroid
300 1.3 km 42 m
1000 540 m 18 m
3000 250 m 8 m
10000 100 m 3 m

“The steam blasts from the water at the crater site rushing back over the hot crater floor will also produce tsunamis following the initial impact tsunami and crustal shifting as a result of the initial impact would produce other tsunamis—a complex train of tsunamis would be created from the initial impact (something not usually shown in disaster movies).”

Text: Nick Strobel, Effects of an Asteroid Impact on Earth, Astronomynotes.com

Image: “The Chelyabinsk event of 15 Feb. 2013, having an energy equivalent to 500 kilotons of TNT, was the largest well-documented meteor event since the Tunguska event of 1908. Analysis of the Chelyabinsk object’s in-atmosphere trajectory from video records has found that its orbit was similar to the orbit of the 2-km-diameter Near-Earth Asteroid 86039 (1999 NC43).There is a possibility that the Chelyabinsk object was created through a collision between asteroid 86039 and another asteroid. It is also very interesting that the Cheyabinsk Asteroid approached from the Sun’s direction, making it essentially undetectable in telescopes” – Analysis of Chelyabinsk meteor and resultant air burst appears in Nature

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New Safe Confinement

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“World leaders jostle with global executives and anonymous men dressed in full camouflage as platters of shrimp, foie gras and cheesecake are passed around by white-gloved staff. It would all seem quite normal were it not for the fact that we’re just 100m (330ft) away from the site of the worst nuclear disaster in history.

“A hospitality tent has been erected just inside the gates of the Chernobyl nuclear power plant near Pripyat in Ukraine. The tent has many windows, to ensure everyone gets a good view of what’s about to happen.

“These guests are here to witness the final stage of a 30-year clean-up job that has been underway, on and off, since one of the plant’s reactors exploded in 1986. The Chernobyl disaster still casts a pall over nuclear power. And other serious accidents, such as that at Fukushima in Japan in 2011 – the only other incident to be classified a maximum Level 7 in the seven-point International Nuclear Event Scale – are weighed against it.

“It also set in train a series of measures to ensure nuclear safety around the world. Now the whole site is about to be encased inside a vast structure known as the sarcophagus, sealing in some of the most dangerous waste material in the world for at least 100 years.

“The behemoth 35,000 tonne structure beside us has spent the past few days inching along a set of purpose built tracks towards its final destination. This sarcophagus – or New Safe Confinement (NSC) – is taller than the Statue of Liberty and larger than Wembley stadium. But what it resembles most is a very large metal shed.

“Its appearance belies its historic importance, however. The NSC is not only the largest object people have ever moved, it’s also a symbol of what we can achieve when the stakes are highest.”

Text: A Vast New Tomb for the Most Dangerous Waste In The World, BBC.com

Pic: Field of Thorns, “But what if the day in question is not today, not tomorrow, but 24,000 years from now, when no known languages are spoken? What if the enemy is not some foreign power, but an ancient civilization? And what if the great threat to human life is no longer a bomb dropping down from above but waste creeping up from below? Will art come to our rescue then?” -WILL ART SAVE OUR DESCENDANTS FROM RADIOACTIVE WASTE?, JSTOR Daily