Torino scale the validity and societal impact of SETI data. The Torino Scale also uses a color code scale: white, green, yellow, orange, red. Each color code has an overall meaning: No object has ever been rated above level 4. The Chicxulub impact, believed by most scientists to be a significant factor in the extinction of the dinosaurs, has been estimated at 100 million (10) megatons, or Torino Scale 10. The impacts which created the Barringer Crater and the Tunguska event in 1908 are both estimated to be in the 3–10 megaton range, corresponding to Torino Scale 8. The 2013 Chelyabinsk meteor
Paired metamorphic belts of plate tectonics in the late 1960s, led to a better understanding of regional metamorphism and permitted the association between paired metamorphic belts and subduction zones. The asymmetric deformation of earth's lithosphere along subduction zones produces two distinct thermal environments. These two distinct thermal conditions are parallel to the trend of the subduction zone. Low temperature, high pressure conditions are generated in the areas along the oceanic trench, whereas high temperature, low pressure conditions are generated beneath the arc region. A positive thermal gradient is visualized, extending from the colder oceanic trench to the warmer arc region. The thermal and