The K/T Extinction

Extinction of the Dinosaurs

The final extinction I will look into is the ever so famous K/T extinction event which lead to the extinction of the dinosaurs. The extinction is the 2^nd largest in the history, behind the Permian, and is thought to have killed off 50% of all species at the time. The event did not have such an effect on mammals, which seemed to sail on through to the tertiary, however marine biodiversity took a large hit (The Department of Paleobiology, n.d.). While it is the most commonly known theory that an asteroid was the catastrophic event which lead to the extinction, it is a touchy subject to some scientists when trying to pin point the exact cause.

Picture Source: http://forum.mafiascum.net/viewtopic.php?p=6455051

There are two main theories about the extinction. The first is that the mass extinction was completely internally driven through volcanism and tectonic movements. The other is the more common theory that an extra-terrestrial object impacted the earth’s surface. Both theories acknowledge these facts: both vertebrates, invertebrates, marine and terrestrial species went extinct; there is a high concentration of iridium found in the K/T boundary layer; iridium can be found either from an extra-terrestrial object, or from deep in the earth’s mantle; and there was a global cooling following the K/T boundary (Smith, 2005).

The first theory suggests that the high iridium concentrations come from the mantle. The cause of this reaching the earth’s surface would be volcanism, and lots of it. It is thought that the extinction was more gradual than catastrophic. The volcanism occurred several million years before the extinction and flooded the earth with lava – evidence for this has been noted especially in India in which the lava flows dated back to 65-70 Mya. The volcanism could have generated enough dust, ash and soot to create a blanket over the earth and block out sunlight, generating a global climate change, a nuclear winter (Smith, 2005). This theory suggests that dinosaurs underwent a gradual approach to extinction.

The second theory is that the earth was struck by an extra-terrestrial object, such as a comet or meteor. The theory was somewhat confirmed to those who believed it in when a crater off the coast of the Yucatan Peninsula, Mexico, was discovered. The crater is 150km wide and dates back to 65million years ago, the year of the K/T extinction. The high abundance of iridium found in the K/T layer, and the shock quartz found within and closely above the layer provides solid evidence for this hypothesis. Following the impact, it is thought that widespread forest fires occurred. However, the impact caused cooling due to the ejecting of dust into the atmosphere, prohibiting sunlight from reaching the earth surface. Some theorists have toyed with idea that there may have been several impact events over the course of serval million years, suggesting the extinction may have been gradual (National Geographic, n.d.).

Currently the exact cause of the mass extinction is unknown. It could well be a combination of all theories – volcanism topped off with an impact event. The overall consensus is that a climate change was the most likely cause of the extinction, seeing as not just one particular type of species were effected. I have already talked about what I believe the threats to humans would be given a rapid climate change, however I have not yet discussed what would happen to humans given an impact event such as a comet. 

I recently watched a ted talk by a man named Stephen Petranek. He spoke about what he believed would be the 10 ways in which the world may end. He believes that the biggest danger to our species is that an extra-terrestrial object collides with our planet, saying it “is not a matter of if, but a matter of when and how big”. I believe it is a huge risk to humans. We are in a fixed orbit, it is a matter which is completely out of one’s control. As Stephen mentions in the video, in 1989, a large asteroid passed 400,000miles away from earth, directly through earth’s orbit. This close call was so close infact, had it been 6 hours earlier it would have collided with earth. Smaller asteroids collide with our planet around every 100 years. They contain enough impact to begin forest fires and kick up enough dust to potentially begin a nuclear winter (Patranek, 2002). The effect of Asteroids colliding with the planet is perhaps not underestimated, but the scale of how often the incident occurs is definitely underestimated. Dr Clark Chapman produced these statistics on what he believed the chances of one being killed by an asteroid/comet impact would be:

This diagram shows the findings of Dr Clark Chapman, presented by Patranek at Ted conference 2002

With the amount of money being spent on preventing deaths in floods, aircraft accidents etc, we should be seriously looking at what we can do to minimise the impacts of this event as it could be deathly should we be so unfortunate. As Stephen mentions at the end of the video, thre are ways to somewhat prevent the issue. NASA is identifying asteroids and predict whether they will encounter earth or not. This technology is more advanced than us being able to predict when a volcano will erupt. Stephen believes that with the knowledge of where the asteroid is heading, scientist can change the trajectory of the asteroid by landing a ion propulsion device on it, and while it may seem farfetched, it is extremely achievable. However because the asteroid theory is not taken as seriously as other possible deathly events in which we potentially encounter daily, without the technology or funding they may well be what could cause our extinction, as it may have the dinosaurs.

Link to TED talk with Stephen Patranek: https://www.ted.com/talks/stephen_petranek_counts_down_to_armageddon#t-1716708

References

National Geographic. (n.d.). Dinosaur Extinction. Retrieved from National Geographic: http://science.nationalgeographic.com/science/prehistoric-world/dinosaur-extinction/

Patranek, S. (2002, February). 10 ways the world could end. 10 ways the world could end. Retrieved September 20, 2015, from https://www.ted.com/talks/stephen_petranek_counts_down_to_armageddon#t-1716708

Smith, D. (2005, September 28). What killed the Dinosaurs? Retrieved from DinoBuzz: http://www.ucmp.berkeley.edu/diapsids/extinctheory.html

The Department of Paleobiology. (n.d.). Extinction of the Dinosaurs. Retrieved from Geologic Time: http://paleobiology.si.edu/geotime/main/htmlversion/cretaceous4.html