Controversies in Science/What killed the dinosaurs/A Critique of Extraterrestrial Cause for the Cretaceous-Tertiary Extinction

(Review Paper) Cited in

Points
The earth was impacted with a large asteroid that send 60 times the asteroids mass into the atmosphere in the form of dust. The dust spread over the earth for several years, causing Cretaceous-Tertiary extinction. The dust blocked the sun which discontinued life for plants since there was no photosynthesis occurring due to the blockage of the sun. This created a chain reaction resulting in the extinction of all food chains. .

Methods
An increase in iridium, that is thought to be of extraterrestrial origin, was found in the limestone of places such as New Zealand, Denmark, and Italy. It dates back to the time of Cretaceous-Tertiary extinction 65 million years ago.

The levels of iridium had an increase of 30 times higher for Italy, 160 times higher for Denmark and 20 times for New Zealand.These high levels play a large role in the extinction on many species.

Results
There is a marked difference between Cretaceous/Tertiary clay and boundary clay. Because the majority of iridium on Earth is found naturally in the planet's core, iridium in the crust was likely deposited by an extraterrestrial source. The impact of the meteor that likely did this would have created a massive dust cloud, hindering photosynthesis and thus killing off the plants first. Since there was no plants for the herbivores they died off next and then the carnivores were the biggest and last organism to die off. .

Iridium is a major component of a meteorite, and it is what was found settled from the global cloud of dust which was caused when the meteorite hit the earth. It was also discovered that this global cloud of dust blocked the sun causing the planet to decrease in temperature also known as The Nuclear Winter

Grains of quarts were found in the K-T boundary layer, and the microscopic traces show proof of shock from the meteorites.