Monday, June 13, 2016

A Little Touch about Mass Extinctions

Life on earth has been plagued with mass extinctions throughout its history. Many scholars cite five, well documented mass extinctions, where between 50% and 90% of all species alive at the time died out. However, at least fifteen other large scale extinction events have been documented. The most famous such event occurred around 65 million years ago and did in the dinosaurs—as well as many other species.

Mass extinctions are due to world-wide (or nearly so) environmental catastrophes that result in drastic alterations to the global climate. An asteroid impact or wide-spread volcanic eruptions can not only directly destroy local environments, but they can throw so much dust and debris into the upper atmosphere that sunlight is greatly diminished. This can cause drastic cooling of the climate and wreck the process of photosynthesis. Once the photosynthetic plants die, everything that feeds on them dies. The carnivores are the next to go.

In 1883, the volcanic island called Krakatoa, which lies in Indonesia near Java, erupted, producing what is generally considered to be the loudest sound ever recorded in modern history. In a series of explosions, roughly two-thirds of the island disintegrated. At least a thousand people were killed immediately, and over 35,000 more died in the tidal waves that followed. (Many believe the death toll to be considerably higher.) Lower temperatures were recorded world-wide in the year after this single event, a little over 2 degrees Fahrenheit on average. It took almost five years for world weather patterns to return to normal.


Krakatoa is not actually the largest volcanic eruption in recorded history, however. First place goes to the earlier 1815 eruption of Mount Tambora, another Indonesian volcano. Over 10,000 people died from the eruption itself, and the deaths of over 70,000 are blamed on the volcano, although many died from starvation. The following year, 1816, is known historically as “the year without a summer.” World-wide effects were detected, but the British Isles and America’s New England states were among the hardest hit. Ice lingered long. Crops failed. People struggled to survive. 

If such single eruption events could have this kind of impact, imagine what the simultaneous or near simultaneous eruptions of many volcanoes could do. It wouldn’t even have to be a great dramatic event. The signs of large scale and long-term volcanism are clearly seen in the geological history of earth. Several of these periods have been correlated in time with mass extinctions. For example, most of Siberia was covered with lava flows around 250 million years ago. The increased volcanic activity in Siberia at that time may have lasted nearly a million years and certainly would have had major impacts on earth’s climate, setting off a cascade of events that collectively shocked the planet’s biosphere. This great volcanic conflagration corresponds with the biggest of the known mass extinctions, the so called “Permian-Triassic event.” Almost 90% of all life on earth perished at that time.

18 comments:

Prashant C. Trikannad said...

Interesting piece on volcanic extinctions, Charles. I suppose, geologically and over time the earth has stabilised as there have been no "great volcanic conflagrations."

oscar case said...

These extinctions were never brought up in my high school geology class, except for the dinosaur episode. I liked the study of that subject, but there was no correlation with the dawn of man or Charles Darwin's Origin of Species. I guess college classes would have been more forthcoming after the basics.

Alex J. Cavanaugh said...

I knew volcanic eruptions could change the climate for a couple years. That happened with Mt. St. Helens as well.

Charles Gramlich said...

Prashant, it's definitely slowed down, although the potential is there. Huge swaths of the world have at times been covered by lava flows.

Oscar, Some of the other mass extinctions have only been identified in the last twenty years so they might not have had that info when you (and I) were in high school, my friend! :)

Alex, yes. good point. I should put that in with my argument.

Cloudia said...

Thanks for scaring the s#%$&t out of me!

Charles Gramlich said...

Cloudia, just doing my part.

the walking man said...

There are preventable smaller extinction events and then there are those completely out of mankind's control. with more science and knowledge we can and usually do overcome the smaller events, say the Bubonic Plague or Polio, but when the planet lets loose with the combined forces working in concert *shrug* I guess one simply must go with the flow.

Charles Gramlich said...

Mark, Yes, once in a while, physics and geology trump biology.

Rachel V. Olivier said...

That gives my brain something to chew on.

sage said...

As for volcanic activity, there were extensive lava flows in the American West around 1000 years ago--but they were not explosive

Charles Gramlich said...

Rachel, I love this kind of stuff. In theory, of course.

Sage, There have been such Lava flows over large parts of the earth, including Siberia. They do cover so much territory though that they do cause long term effects. We saw a couple of lava fields when we were out west a few years ago. Very impressive.

David Cranmer said...

I agree with Stephen Hawking that we need to get off the planet to survive as a species.

Charles Gramlich said...

David, agreed as well

G. B. Miller said...

I knew about the first one mentioned, mostly from reading very strange non-fiction books. The 2nd I've only seen mentioned in light passing in a few historical fiction books.

Suppose global warming happened even back then, eh?

Charles Gramlich said...

G. B., A lot of extremely dramatic climate shifts have happened on Earth in the past due strictly to natural causes. It doesn't mean that humans could not become a cause in addition, but certainly not the only thing that has ever caused climate shifts.

Bernard Lee DeLeo said...

I remember when Mount Pinatubo erupted in 1991. It spewed out more ozone depleting chemicals into the stratosphere than all of mankind. The eruption was unpreventable, just as solar storms, and climate cycles. That event and your excellent post remind us how very little we have to do with our environment on a cataclysmic global stage.

Riot Kitty said...

Well, you are just a ray of fucking sunshine! ;)

Snowbrush said...

It’s interesting to think that, despite our specie's determined efforts to destroy life on earth, an asteroid or a volcano might come along and do it first, and that this would be true even if we lived with wisdom and goodwill instead of greed and stupidity.