Things to Worry About

• On April 13, 2036, the asteroid 99942 Apophis will strike the earth with a probability of about 1:5900. Apophis, which is about 320 m in diameter and has an approximate mass of 4.6×10¹⁰ kg, would have the effect of a 880 megaton explosion if it hit; for comparison, Krakotoa was about 200 megatons.
• On June 3, 2048, the asteroid 2007 VK14 will strike earth with a probability of about 1:2900. 2007 VK 14 has an estimated mass of 3.3×10⁹.
• On May 28, 2057, the asteroid 2005 WY55 will strike the earth with a probability of about 1:8200. The diameter of 2005 WY55 is estimated at between 210 and 480 meters.
• On May 4, 2102, the asteroid 2004 VD17 will strike the earth with a probability of about 1:1600. 2004 VD17 is about 580 m in diameter, with a mass estimated at 2.7×10¹¹ kg. An impact would have an estimated effect of 15,000 megatons.
• The asteroid 1999 RQ36 has numerous possibilities for colliding with earth in the twenty-second century, with a cumulative probability of about 1:1000.
• On March 16, 2880, the asteroid 1950 DA will strike the earth with a probability of at most 1:300. The size and mass of 1950 DA are poorly known, but since it is over 1 km in diameter an impact would be expected to cause global devastation.
• A "supervolcano" eruption, which would dramatically cool global climate for several years, could occur at any time. The last such eruption may have occurred 74,000 years ago, when the Toba eruption (in what is now Indonesia) cooled temperatures in the Northern Hemisphere so much that it has been estimated that three-fourths of plants there died. One past and probable future supervolcano is Yellowstone, which last erupted on this scale 640,000 years ago; if repeated today, it would cover half the United States with 3 meters of ash.