We are all familiar with the Armageddon-type movies where a giant meteorite comes racing towards the Earth with remarkably short notice, only to be stopped at the last moment by a crew of handsome scientists. However, while such an event could potentially mean the end of most life on Earth, new research suggests that it is actually not the size but rather the impact location that determines whether or not the meteor will cause a mass extinction effect.
The study, published in the Journal of the Geological Society by Dr. Matthew Pankhurst and his team explores why some meteors caused mass extinction effects, while others did not. The best example is the meteor that killed the dinosaurs, which was much smaller than several other meteors that hardly disrupted life at all when they impacted.
Key factor the soil composition of impact site
A team was formed, consisting of experts on asteroid composition, mineralogy, paleontology and the climate, working together on this mystery by studying 33 known asteroid impacts that happened in the last half a billion years. Their focus was on the meteor size, mass and composition, but also the surrounding area and the minerals found in the dust that would be launched into the atmosphere by the impact.
Their findings showed that mass extinction effects were in fact much stronger related to the soil composition of the impact site than the meteor itself, thus proving their earlier theory.
Kfs crystalize water forming transparent clouds
In fact, the most important variable turned out to be the amount of potassium feldspar (Chemical name Kfs) in the ground. This is a so-called ice-nucleating mineral, which means that water more readily crystalizes around it, and stays a solid at higher temperatures.
Impacts without much Kfs in the soil would cause a cold period due to all the dust that is thrown up into the atmosphere, but this would not take much longer than a year or so to improve. However, Kfs can stay up in the sky for thousands and even hundreds of thousands of years, affecting the clouds by crystalizing the water and thus making them much more transparent.
Transparent clouds are a bad thing, as they take away the Earth’s balancing power. A cold planet will have few clouds, allowing the Sun to heat it up. A warm planet will have a lot of clouds, which keep out the sunlight and thus help cool the planet down. Transparent clouds on the other hand do not stop the heating of the planet, resulting in a runaway effect that Pankhurst believes is the reason for meteor-related mass-extinction events.
Pankhurst’s team will now focus on the actual heating period, and try to understand how these periods cause the extinctions and how long they last. Knowledge that might help us better understand the impact of man-made climate change.