(I wrote this article about a year ago, but in light of this month's earthquakes in New Zealand and Japan, I though it appropriate to represent it for people's consideration.)Watching the news and reading the headlines on the internet would lead one to believe that late 2009 and 2010 thus far has seen an unusual number of geotectonic events. I have often thought, and heard more than a few say, that the perceived increase in seismic activity is due to our contemporary profusion of information sources and that there really hasn’t been an actual increase in geotectonic activity. On the subject of earthquakes, the experts at the USGS agree with this view: http://www.usgs.gov/newsroom/article.asp?ID=2439.
See also http://www.enn.com/climate/article/41234.
This recent perceived increase in seismic activity may speak more to mankind’s habitation of more of the Earth’s surface in higher numbers than ever before. Although, like the kernel of truth contained at the core of every myth, I cannot help but think that there may be some truth to the idea that the Earth’s surface is on the move a little more than before. I also wonder if there has been an increase in volcanic activity recently. Although my cursory search hasn’t led to any credible sources supporting or refuting the notion of recently increased volcanic activity, I have found one article from The Guardian (UK) that at least implies that volcanic activity is on the rise: http://www.guardian.co.uk/science/2007/aug/07/disasters
This article written by Bill McGuire, the director of the Benfield Hazard Research Centre at University College of London, attributes what may be an increase in recent volcanism to a higher volume of near-surface magma caused by the increased surface pressure on the Earth’s crust due to higher sea levels attributable to global warming induced glacier melt. Basically, that more water in the oceans squeezes the Earth, and volcanoes erupt as a result. One crack that I see in this idea is that the scope of the hypothesis is entirely internal to a closed system. The Earth has not received a large deposit of water recently so it’s fair to say that what was here before is still here now. From a material standpoint, the system has not changed. The sea-level connection to increased volcanism requires that the particular distribution of the material in the closed system be the cause of the observed effect. This may be plausible because large amounts of water locked up in glaciers, which are highly localized, causes a very different pressure distribution on the Earth’s crust then the same amount of material spread over a much larger area in the form of water. I am not here to refute the possibility that this idea may be the truth, but I would like to put forth another explanation for the rise in volcanic activity particularly and geotectonic activity in general: The Sun.
Throughout our history, mankind has held an ever-changing view of what his world was like. At one time, the Earth’s geologic features were thought to be the bones of titans laid low by the gods in the starry heavens above. Then we moved to a concept of the Earth as one whole, in the center of all that was, and surrounded by successively more distant spheres of the heavens. Next, we removed the idea of the spheres when we realized that the things not of this Earth were in fact unique objects of their own at some knowable distance away from the Earth. From there we formed the idea of the solar system with the Earth at its center and at the center of all things. Then the sun was at the center, but was still the center of all things. That view was dashed when we found that our star was but one of many which revolved around a common center as part of our galaxy. We essentially find ourselves at this view today. Our prior obsession with the center has carried over into our contemporary consciousness in that even though we understand that our solar system is not at the center of anything, we still think that the Sun is at the center of our solar system. This in fact is not the case. Astronomical scholars know this, but when considering the effects of our Sun’s eccentricity I believe that one certain effect, naturally part of this eccentric system, has been overlooked.
The things in our solar system each have a mass which produces a certain amount of gravity, are arranged in a particular fashion at different points in time, and are moving at certain speeds. All of these properties exist in such a way that dynamic equilibrium within the system is maintained. Dynama-what? Assuming that our solar system is a closed system, meaning that it doesn’t receive any input from forces that originate from outside of the system which is essentially true, this dynamic equilibrium is an equilibrium in which opposite changes occur simultaneously; an equilibrium in which two reversible reactions occur at the same rate. When one planet moves, its change in position with respect to all of the other objects causes the effects of its gravity on all the other objects to change. In response the effects of gravity from all of the other objects on the planet that moved change with respect to that planet in its new position. This is an example of Newton’s 3rd Law of Motion that, “To every action there is always an equal and opposite reaction: or the forces of two bodies on each other are always equal and are directed in opposite directions (Actioni contrariam semper et æqualem esse reactionem: sive corporum duorum actiones in se mutuo semper esse æquales et in partes contrarias dirigi).”
An extremely simplistic analogy of the situation described above is that every object in our solar system is connected to every other object in our solar system with a “string”. As the system moves and rotates, these “strings” get longer or shorter as the distance between the objects changes. The force in each of these “strings” is inversely proportional to its length. That is the shorter a “string” is the harder it tries to get shorter. As you may have guessed already, these “strings” in combination with their internal forces as described above represent gravity. The magnitude of the gravity produced by each object is in direct proportion to its mass. Of the mass in our solar system, the Sun accounts for 99.87% of it. The mass of Jupiter accounts for 73.42% of the remaining mass or roughly 0.1% of the total mass of the system. It would seem that the Sun is the 800 lb. gorilla and that the effects of everything else are negligible which is essentially correct except for one effect. If we say that everything other than the Sun and Jupiter are along for the ride then we’re left with two objects connected with one string. Jupiter appears to orbit about the Sun, which cannot be correct because of the assumption that the Sun is stationary and remains stationary. Equilibrium cannot be maintained because as Jupiter rotates, its gravity pulls on the Sun causing it to begin to move. The system has changed and cannot be said to have remained in equilibrium. The reality is that both the Sun and Jupiter are rotating about a common point, and that the mass of Jupiter times its distance to this point is equal to the mass of the Sun times its distance to the point. One very large mass times a very small distance is equal to a very small mass times a very large distance. This point of common rotation is called the barycenter.
Why go to such length to create an analogy to describe the barycenter, and what does the interaction between Jupiter and the Sun have to do with the geotectonics of Earth? The analogy distills the system into something that we can comprehend by testing it with our bodies rather than just our minds. Hold a string that is a couple of feet long and is attached to a small ball. Swing the ball around until it is moving in a circle. Can you continue swinging the ball in a circle at the same speed without swinging your hand in a circle? No, and you will notice that the circle that your hand makes about a common point of rotation with the ball is much smaller than the circle that the ball makes. Your hand is acting like the Sun in this system. Now also notice that the string between your hand and the ball has a tensile force in it. That centripetal force is equal to the ball’s mass times the square of its velocity, divided by its distance to the “barycenter”. What happens when you spin the ball faster? This centripetal force gets larger, and to do this the radius between the “barycenter” and your hand must get smaller as your hand speeds up. Kepler found this relationship when he discovered that the planets move in elliptical orbits.
What does this have to do with the Earth? Well, the weight of the ball at the end of the string is mostly Jupiter. It can be said though that it is also all of the other stuff in the solar system other than the Sun, and the length of the string is the distance between the center of the Sun and the “center of mass” of everything else. When the distance between the Sun and the barycenter gets smaller, the velocity of the sun relative to the barycenter increases, and the centripetal force exerted on the ball gets larger. The converse of this statement is also true that, the distance between the center of planetary mass and the barycenter gets smaller, the velocity of the planetary mass relative to the barycenter increases, and the centripetal force exerted on the Sun gets larger. Thus angular momentum is conserved. So if the force between the planetary mass and the Sun gets larger, and the Earth is part of this mass, then the force exerted between the Sun and the Earth gets larger. The shape of the Earth must change when it is subjected to a higher centripetal force according to the principles of material mechanics. If the Earth is changing shape, even by a few feet, this change must be accounted for by deforming its surface from where it was initially. Hence, earthquakes and volcanic eruptions could result in either increased frequency, magnitude, or both. Conversely, this additional force may act to squeeze everything together resulting in a noticeable decrease in geotectonic activity.
This is all a very neat hypothetical situation that hinges on the premise that the Sun’s distance to the barycenter changes. We must ask ourselves, “Does it change?” A geologist from Australia named Rhodes Fairbridge answered this question. Beginning in 1950, he began to research a unique geological phenomenon along the coast Western Australia and subsequently the coast of the Hudson Bay in Canada as well as other places around the world. His conclusion was that there had been substantial changes in the climate and the sea level over recent geological time that caused these unique phenomena. Furthermore, he put forth the possibility that these environmental factors were highly periodic.
Through a lifetime of research and continual cross-disciplinary coordination, he discovered several things. First, he discovered that the Sun’s characteristic radiation output has varied periodically through time between high activity and relative quiet. In searching for a cause for this observation, he discovered that the Sun’s orbit around the barycenter is not round or even elliptical. Rather, the Sun’s orbit is in the shape of an epitrochoid, which is a circle that contains a tight elliptical loop-the-loop at one point around its circumference, and that these solar variations corresponded to the Sun’s passage through this loop-the-loop. Although Professor Fairbridge focused on the effect that the Sun’s epitrochoidal orbit had on its radiative characteristics, our foregoing discussion reveals that the orbit may also affect the internal inertial forces of the solar system.
Contrary to what I implied above, the Sun approaching the barycenter does not cause the planetary center of mass to approach the barycenter or accelerate. Instead it’s the other way around. When Saturn and Jupiter are in opposition, as they are now in early 2010, the center of planetary mass as well as the Sun’s mass is as close to the barycenter as possible. This positioning of the planetary mass, barycenter, and Solar mass produces the greatest amount of angular velocity as well as centripetal force in the system. Conversely, when Saturn and Jupiter are in conjunction, the system has its least amount of angular momentum and centripetal force as the Sun is at it farthest point from the barycenter.
The potential effects of the Sun’s angular momentum on the solar dynamo and cycles of solar activity are fascinating and could have profound implications on our understanding of the Sun’s impact on our climate. A summary of Professor Fairbridge’s work in this direction of study can be found here: http://www.griffith.edu.au/conference/ics2007/pdf/ICS176.pdf
Additionally, I believe that the centripetal effects on the planets of the solar system produced by this characteristic orbital shape are worth serious consideration as to their possible implications in the study of seismology, volcanology, and geotectonics in general.
