Hot-Spots and Tectonic Plate Directional Vectors

Something I have casually wondered about ever since I first heard of these hot spots. Are they more or less permanently located? They seem to remain for tens of millions of years at least, which, if not permanent, is almighty persistent!

In studying plate motion I have seen hot spots used as reference points. I never quite believed that a isolated convection cycle in such a dynamic environment could bypass the external forces that might act on it.

When viewing diagrams with plate velocity vectors, I believe we see Africa nearly stationary while ocean ridges exist on opposing borders. If Mid-Ocean ridges are not stationary can we prove that the exact location of some hot spots are indeed in motion as well?

Personally, I think Hawaii is a special case.

http://commons.wikimedia.org/wiki/Image:Tectonic_plates_boundaries_detailed-fr.svg

It's special for sure, there's something non-standard going on! I concur that the environs are far more dynamic than I would expect something like a convection cycle to stand mostly still in either. Seems to me it would be equal to a whirlpool standing still going over Niagra Falls.

Still, those velocity vectors may be somewhat misrepresented. Something has to be used as a reference point, but it may be illusory to think of any part of the surface to be absolutely stationary (or anything like stationary) in the long run.

When they build those models I believe they use the rotational inertia about earth axis of rotation and possibly a second seemingly fixed point. Most computer models and journal articles I have read support the idea that Africa is seemingly fixed and more so the volcanic activity observed in Hawaii. I believe the model is pretty close. I just don't know of any true point of reference and have my doubts any other hot spots behave as well as the Hawaiian example.

http://www.sciencemag.org/cgi/content/abstract/175/4028/1355?ck=nck

Hi,

why shall the Hot-Spots be stationary?

official theory says so but without any arguments.

In contrary I am convinced that Hot-Spots are not stationary:

rising plumes in a viscous fluid are like tobacco smoke from the tip of a cigarette that is rising in air (no wind-speed). May be the viscosity is much higher so we should calculate the Reynolds number to estimate onset of first vortices.

If Re is below 1 so that there are no vortices at all then there are the electromagnetic forces from a moving conductor in a magnetic field.

This not enough there are Coriolis forces at rising material as the velocity near the center of earth is lower than near the surface. This causing a westward deviation.

We have no inertial frame to detect the motion so we cannot distinguish plate motion from hot-spot motion.

What would interest me: how much material is rising at which velocity in a hot spot?

How much of this will come to surface as a volcanic eruption?

I am living not too far from a hot spot that can be traced for the last 1.5x10⁹years, starting the Eifel-volcanoes in Germany beginning 25 million years ago and the last eruption 10,000years ago ( a really big one) and a ready to move upwards magma-chamber waiting for the next eruption.

Not very likely that we will see it but if: then dramatic.

RHABE

Our Yellowstone seems similar. It's said to be a potential volcano of enormous proportion waiting to erupt. Personally, I don't need such drama, but I suppose there's not a whole lot of choice involved...

I agree that the fixed location of a hot spot seems most likely, yet the Hawaii-Emperor Seamount Chain accurately describes the plate motion of the Pacific plate for the last 80 million years. The sharp bend around 40-50MYA correlates with the separation of Australia-New Guinea from Antarctica as well as the collision of the Indian plate with the Eurasian Plate.

80 MYA may not be a long time for a convection cycle within Earth's crust, yet they hot-spot feeding the Hawaiian Islands seems to have had been fed by a critically hot mass that continues to rise with heat and velocity that remains unscathed by any external forces.

I know the observational evidence for at least some hot spots remaining more or less stationary, but as RHABE mentioned, there has to be some sort of justification for this being so. We can't just postulate that it seems so, therefore it is so. There has to be a description of the likely mechanism, or it's just another case of "at this point, a miracle occurs". What good is that?

Its obviously a deep epicenter convection cycle. Most likely originating far beneath the massive convection cycles that feed the mid ocean ridges. The beauty is that there is no direct observation as to what feeds these anomalies.

We know they exist and feed plumes of hot magma that melt away a shallow pool in the lithosphere. The fact that they remain stationary argumentively disproves that basal drag is a major driving force in plate tectonics.

Possibly, extremely thick oceanic plates that become subducted are unable to heat uniformly and some mass sinks below existing convection cycles. This mass could displace or eventually heat up and escape the D" layer? Rising at great velocity so that it eats through the slow moving outer mantle like a hot knife through butter.

The turbulence could streamline the flow until the hot-spot weakens as we have not yet seen in Hawaii where we would expect it to lose stability, wonder and posisbly die-off. Who knows how long that could take?

Obviously it takes at least several tens of millions of years.

"...Rising at great velocity..."

Great being a relative term, of course. But sure, why not huge chunks of more-or-less consolidated plate material. It could act as a flow diverter or constricter. But would this maintain its function over that long a time?

Oceanic crust on average is surfaced for about 200 Million years. Beyond this time span you may consider it to be abnormally thick, and since oceanic crust is destined to be consumed by the convection cycle after subduction I would expect such a cycle to exist for at least 200 million years.

I wouldn't offer a theorem if I didn't believe it held some water. I would also expect most people to be highly subjective in believing such a statement, and I open the floor to anyone that has a better theory as to why these anomalies exist and what force could possibly feed them. Are they related to magnetic reversals?

"Are they related to magnetic reversals?"

Hadn't thought of that, and if I ever get free time to research the potential timelines, I'll try to form an educated opinion.

I can't take the sole credit for my suggestions. It is an area in Geology that there has been a lot of throwing our hands in the air due to limiting data sets or inability to measure.

The following paper suggests that there are multiple mechanism that can induce hot-spots. Please remember that plate tectonics is a developing science and that many specifics are still left as a fronteir.

http://www.sciencemag.org/cgi/content/summary/300/5621/920

Yellowstone is similar in action but much bigger in size.

From the last eruption of "Laacher See volcano" there remains only a small (1km diameter) Maar = craterlake where a famous medieval monastery is situated.

Nearby (30km) Rhine-valley has covers of lapilli only 25m thick.

RHABE