13 May 2011


There are about 60 scientists in the US Geological Survey who volunteer on their own time to reply to questions that come in via Ask-a-Geologist.  This is a place on the USGS website where anyone can ask a question and get an answer from a geoscientist.  Almost half the questions are spam - surprisingly, most of these are in Portuguese (no, we don't understand that either).  About a quarter of the questions are from school children trying to get someone else to do their homework assignment for them.  These are pretty obvious, and by policy we are asked not to encourage this (but we usually answer them anyway).

Today I received three questions, and they were interesting.  I share one of them with you all because I hope it might answer some of the questions that from newspapers are definitely floating out there:

Hello..I was just wondering first if the increased number of earthquakes is a sign of something bigger to come and since the earthquake in Japan knocked our earth off of its axis a few feet is that the reason for the severe weather we have had lately like all the floods in the south and tornados and severe storms any info would be great. thanks so much

The Earth's axis was tilted about 10 cm by the Tohoku earthquake - that's about 4 inches.  It requires some very sophisticated equipment and a lot of measurement time to arrive at that tiny amount of offset.

While there is evidence that continents were at hugely different latitudes in ages past (dinosaur skeletons have been recovered from Antarctica), a 10-cm tilt-change will not cause any measurable effect.  A long and slow tilt change in the Earth's axis has been documented over time, and can be explained by simple orbital mechanics, but the operative word here is "slow" - we're talking many millions of years type of slow.  There is also the complication that the continental plates have been moving around at the same time.  Uhhh... so where's the observation point then?  Since we didn't have observers using sextants to track where Polaris is/was 50 million years ago, these things are understandably hard to sort out.

There is an on-going discussion about earthquakes triggering other earthquakes.  Large earthquakes have been shown to "light up" volcanic areas like Yellowstone and Long Valley with short-term clusters of increased micro-earthquakes.  However, the current scientific consensus, culled from literally petabytes of data collected over the past 50 years, is that distant earthquakes do not have any effect on faults not part of the earthquake's own fault system.  In other words, the monster earthquake in Chile last Spring did not trigger the huge earthquake in New Zealand last Fall, and that one didn't trigger the ginormous Tohoku earthquake this past March near Sendai Japan.  Among other things, there were months separating each one.  Also, an earthquake’s energy falls off as approximately distance squared, so if YOU didn't feel these, neither did the other distant subduction faults that blew later on.  Researchers have studied syzygy - the effects of Sun and Moon tides - on earthquakes, and have found no statistical correlation.  

All THAT said, there HAS been a measurable, undeniable, and steadily ramping-up increase in the carbon dioxide content of the Earth's atmosphere in the last several centuries.  CO2 has a measurable greenhouse effect on atmospheric temperatures.  Methane, however - and there are far more cows now than a century ago because there are more people feeling they deserve beef steak - has far more of a greenhouse effect for the number of molecules released (it's 37 times more potent, and I'm not talking odor here).  Virtually all scientists not paid to say otherwise readily acknowledge that there is a large anthropogenic component to this increase - i.e., humans burning hydrocarbons, destroying forests, raising flatulent steers, etc. are mostly responsible for these increased gases in our atmosphere.  If you haven’t ridden a horse recently, you probably wouldn’t believe how much methane a grass-chewing critter can produce.  Hoooeyyy.

It's still being argued - mainly through ever-increasingly-sophisticated mathematical models - just how much all this increase in greenhouse gas emissions has actually changed our weather.  There are a huge number of variables involved, so one model may disagree with another in detail - but not in gross conclusions.  “We has met the enemy, and he is us,” said Pogo.  There are certain undeniable influences on weather (the Solar flux and the great ocean currents like the Gulf Stream, for instance).

However, you and I may not remember huge hurricanes and tornado clusters from our childhood, but that may just be our imperfect memory.  The apparent increase in wild weather events over the past few decades may also be an artifact of how records have become increasingly more detailed and complete over time.  Keep in mind that earthquakes - and probably to some extent anomalous weather events - are to varying degrees random things.  They don't come on the hour, or on Friday the 13th, but often have gaps and then appear in clusters - and we remember the most recent cluster best.  That’s the human mind for you (and why scientists carefully record their data).  Using a statistically more reliable approach - averaging and comparing hurricanes and their strengths for say, the 19th Century against the 20th Century - we are also hamstrung by the fact that there were far fewer people 150 years ago... and correspondingly fewer and sparser records kept then.  

Bottom line(s): Climate change is here, and it is apparently accelerating.  Earthquakes are random and not predictable.  Neither affects the other.  

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