The Year Without A Summer

In 1815 Mount Tambora, located in Indonesia, exploded in history’s most calamitous volcanic eruption.  More than 70,000 people were killed.  The summit of the mountain was reduced from 4,300 meters to less than 2,900 meters.  The explosive yield of this eruption has been estimated at about 800 megatons.  This was a nasty neighbor.  The larger effects would not be felt for a while, though.

Tambora was to have a lasting impact on the global climate, but it did have some help.  In 1812 La Soufriere in the Caribbean erupted, as did Mayon in the Philippines in 1814; those two volcanoes had already put a significant amount of ash into the atmosphere.  Additionally, the Sun was in a period of lower activity, so the stage was set for Tambora’s dramatic entrance.  When Tambora’s 800 megaton blast occurred, more than ninety cubic miles of volcanic ash was blasted into the atmosphere.  That tremendous load of ash coupled with the ash already present in the atmosphere from the two previous eruptions, as well as the sun’s lower activity resulted in 1816 being called the Year Without a Summer.

Unusually late frost hit New England and Eastern Canada in the spring of 1816 virtually wiping out the crops that were already in the ground, and the following month two huge snowstorms killed many people.  This snow also killed the crops that had survived the earlier frost, leading to famine; people, their vitality sapped by hunger and malnutrition, began to die from disease.  So little rain fell in July and August, drought damage stunted the crops that had managed to hold on.  Reduced sunlight prevented crops from growing and maturing, even if they could survive the cold and drought.

Other parts of the world fared no better.  England experienced greatly increased rain, and reduced temperatures; this resulted in crop failures.  Many parts of mainland Europe experienced crop failures.  Because of the Napoleonic wars, Europe was already having problems with shortages of food; the crop failures exacerbated this problem.  Riots and looting ensued, as did famine.  There was extensive flooding of numerous rivers because of increased rainfall.  About 200,000 people died as the result of famine and disease.  Asia had unusually low temperatures (including frost), and heavy monsoons.  Rice production was drastically reduced, and famine and disease were widespread.

That was quite a party Tabora threw.  It is just a good thing it doesn’t go to that much trouble very often.  There have been worse eruptions, though.  I will talk about just one more next time.

Our planet has pimples

Just as some pubescent humans have problems with acne, so too does the Earth have its face dotted with zits.  Just as a teenager’s pimples can release viscous fluids, Earth’s can spew also.  The analogy breaks down at this point, because while a teenager’s acne can be very embarrassing, our planet’s volcanoes can be incredibly dangerous.

Even the most predictable and mild-mannered volcano is not something you would want to have as a neighbor.  The polite volcanoes are not the subject of this discussion, though.  Neither are the locally obnoxious mountains of fire; the citizens of Pompeii and Herculaneum had their day ruined by Vesuvius in the first century AD, and while that eruption was a terrifying disaster for the people of the area, that event had little impact on the lives of people around the world.  We are looking for volcanic events that tinkered with the climate, or had an effect on life around the world.

When Mt Pinatubo erupted in the early 1990s, it was the second biggest eruption to take place in the Twentieth Century.  In less than two hours the ash and gases produced by Pinatubo penetrated the atmosphere to an altitude of over thirty kilometers.  During this eruption Pinatubo produced as much as thirty million tons of sulfur dioxide, and within a year this cloud of gas was distributed worldwide, cooling the planet by more than half a degree.  Admittedly, half a degree doesn’t sound like much, but when you are talking about the global climate it is pretty amazing that the eruption of one little volcano can have that much influence.

Next time let’s look at a little bigger eruption.

A nasty neighbor that won't stay away

In late 2004 a near-Earth asteroid was discovered that considerably reduced the giggle-factor usually associated with discussions of asteroid impacts.  It was called 2004 MN4.  In mid-2005 it received a permanent number, 99942, and a month later it got a name:  Apophis, after the Greek name for the Egyptian god of darkness, destruction, and evil; it was an appropriate name.

As preliminary data came in and was analyzed, a chilling picture started to take shape.  While this rock was not nearly as big as the Chicxulub asteroid, it would dwarf the Barringer and Tunguska impactors; Apophis is almost three hundred meters in diameter.  The calculated yield for its impact was nearly a thousand megatons.  By comparison, the Tunguska and Barringer impacts gave about one to three per cent of that yield, and the Krakatoa volcanic explosion of the late 1800s produced only (ha, only) about 200 megatons.  

If Apophis hit a populated area the casualties could number in the tens of millions.  An impact in the middle of the north Atlantic would produce cataclysmic tsumanis for the east coast of the United States and the west coast of Europe; the Caribbean islands could be wiped clean.  The news got worse: the first calculations gave odds of an impact in 2029 at 1 in 233, and it received a 2 rating on the Torino scale for impact hazard.  Not bad odds, but the potential consequences as summarized above were horrific.  As more data became available over the next several days the odds got much worse, at one point the chances worsened to 1 in 37 for that 2029 meeting.  Fortunately, given our pathetic state of readiness to take any remedial action, the observations and subsequent calculations over the following weeks and months revealed much better forecasts for us.  Apophis will almost certainly miss the Earth in 2029.  During that encounter, Apophis will pass within the orbit of our geosynchronous satellites; that encounter will be on Friday, April 13.  In 2036 we will have another close approach with Apophis.

What happens during our 2036 encounter with Apophis will depend on the exact trajectory of Apophis in the 2029 encounter.  The orbit of Apophis will change because of its 2029 encounter; the amount of change hinges on how closely it approaches Earth.  If Apophis passes through a gravitational keyhole, a tiny region of space near Earth so that our gravity gives it precisely the right (or should that be the wrong?) nudge, Apophis will collide with Earth in 2036.  The chances for hitting that keyhole stand at 1 in 45,000.  That sounds like very long odds, but it is many times more likely than for any one individual dying in an airplane accident.

We have an identified threat, and we have some time to do something about it.  We do not know if there are other threats of the same kind with a shorter time-frame.  We should not wait until the last minute to develop the capability to mitigate this kind of threat.  Likewise, we should not wait to develop the capability to detect other potential threats of the same nature.

All right, I am through beating you over the head about rocks from space.  Next I want to explore some other ways we could be knocked back to the Stone Age.

How big of a hole does it take to worry you?

I have been away for too long.  My excuse is that I experienced a turkey-induced food coma, and with all the turkey leftovers it lasted quite a while.  That is my story and I am sticking with it!

Let's get on with the search for the big holes, the ones from the truly scary rocks.  

The name is Chicxulub.  It sounds exotic.  Chicxulub is not a high-dollar, trendy resort frequented by equally high-dollar, trendy people.  Chicxulub is not a vacation destination, but it is tropical.  Chicxulub is straight south of New Orleans across the Gulf of Mexico, and a little over 300 kilometers west of Cancun.  Once upon a time, more than just a few years ago, the place that would become known as Chicxulub was a scene of unimaginable destruction.  We do not know if the day was sunny or overcast, indeed we do not know if it was daytime at all.  There were no people around to witness the event; that is a good thing, because most of the life on this planet was probably snuffed out.  An asteroid approximately 10 kilometers in diameter slammed into our lovely planet.  (Just to get an idea of the size of this thing, at the instant the asteroid first touched the surface of the Earth, the other side of the asteroid was just about at the cruising altitude of our airliners.)  The ground splashed, like a mud puddle when a child throws a pebble into it.  Uncountable tons of rock and dust was blasted into the upper atmosphere.  Hot debris rained down world-wide, and estimates as high as ninety percent of the world’s biomass burned.  Some of the biggest megatsunamis this poor planet has ever seen resulted from the impact; some of them were perhaps a half a mile high.  The blast yield of this impact has been estimated to exceed 100 million megatons.  The shock likely triggered earthquakes around the world, as well as extensive volcanic activity.  The dust and other debris in the atmosphere would have lingered for years, blocking out sunlight and therefore putting a halt to plant life.  The resulting crater (as measured today) is more than 180 kilometers across.  This little party is referred to as the K/T event; it ended the Cretaceous Period and began the Tertiary Period.  (There is still some debate whether the Chicxulub impact killed off the dinosaurs or not.  However, even some of the critics of asteroid as dino-killer theory accept it as a contributor to their demise.)

Are there even bigger holes?  Well, yes.  There are, although there are not many and they are not a great deal bigger.   Are we likely to experience a similar event?  Eventually, with certainty.   Soon, almost certainly not.  However, we do not need to be threatened with the sterilization of our planet to have a very bad day.

I am almost through talking about party-crashers.  I do want to mention a rather unsavory neighbor that paid us a fleeting visit fairly recently, and has promised to come back.  I will deal with that topic next time.