The History Channel had a recent show about the extinction of the dinosaurs. In examining possible causes the most prominent theories revolved around climate change, volcanic eruptions, disease, and meteor impact. It was clear from the show that the reason for the extinction is still in question. One paleontologist suggested that by the time the Earth was struck by a meteor(s), most of the dinosaurs were already dead. Disease may have occurred, largely due to changing land masses that enabled microbes to travel to new places and destroy those lacking immunity. Yet, why would they all die out-including those who lived in the sea? Major volcanic eruptions in places like India and elsewhere may certainly have poisoned the air-and yet, mammals survived. Climate change? Certainly ice ages and/or warming would eliminate many, but not all. The meteor? Okay, possible, but evidence of massive piles of dead dinos may not support this.
Okay, so the bottom line is that we don't have a final answer. Further, we read that, "The K-T extinction was not the first such massive die-off in history, nor was it the largest. The Permian-Triassic extinction event, known as the Great Dying, occurred 251.4 million years ago and eradicated 96 percent of all marine species and 70 percent of all terrestrial vertebrates species on earth."
So, do meteors periodically kill off life on earth, or do cycles occur that totally alter the planet, as a kind of cleansing, that starts things anew?
So where do we stand today? A die off, mass extinction six, is occurring that is driven by humanity. And, being the cause, we seem to think that perhaps we are immune to the extinction mania that has plagued our dear Mother Earth. Hmm, plague? Perhaps Mother cleanses herself periodically. But that is another topic. However, let's take a quick look at the world and see if we are really in possible trouble.
Have there been many recent volcanic eruptions? Here's some interesting data:
Using the Smithsonian Volcano Research database and sampling every five years the following trend for eruptions is shown for the past 150 years.
Okay, I only show back to 1900 but the trend is clear.
Climate change? If your head is in the sand you may not have noticed but, yeah, there is major climate change that may not be conducive to continued human habitation.
Disease? Yup, despite vaccinations and advances in science, some oldies but baddies are re-emerging. And, while new land bridges may have allowed the spread of pathogens to the dinosaurs, our 'global' economy has created the same condition. Just look at all of the reports of invasive species and the spreading of new diseases.
What are we missing? Ahh, the meteor. Maybe yes and maybe no. Astronomers are discovering new ones all of the time and we have had so e near misses.
And, I almost forgot solar/stellar radiation from solar flares and quasars. We are near Solarmax and there are some close exploding stars.
2012 is drawing nigh and the hand we are playing in the cosmic poker game may be a definite loser. We can bluff ourselves into thinking that the game will go on forever, but...