The earthquakes started mainly within the First Polygon, but then spread northwards along the central NS-axis of the Second Polygon shown on the picture above.
Also, it is interesting to see how the earthquakes spread north of Skagafjörður, the old volcanic zone, which has been volcanically extinct for a few hundred thousand years, but is still seismically and geothermally active.
Analyzing the convection within Earth’s mantle is actually very easy. The layers of Earth have been measured, and each of them is a layer of convection. Physics tell us convection of the mantle should be in the form of convection rolls. The shape of the rolls must be in accordance with the shape of the Earth. Thereby we know the basics, and can make use of our knowlegde, understanding the geology better.
Earth’s Layers and the Convecction Rolls
Between the large scale rolls and the tectonic plates, there are two layers. Also, there is a special system for the poles, and a system extending from equator. These system intersect each other, forming a transition zone. The central axis of transition zone is 64°N. The picture above shows the central axis of 64°N. Therefore, there are 4 layers found between the large scale rolls and the tectonic plates.
The two layers from south become the lower convection rolls. The polar system is composed of the upper more convection rolls of the transition zone.
We are so lucky that the weather system follows the same rule. So those who have studied meteorolgy might see the analogy. here. Southern winds along the ground rise and head back. Northern winds also rise and find their way back. The result of the transition is also four layers, exactly at the same latitudes.
The Reykjanes Ridge is mainly shaped by the equatorial system of convection rolls, but the direction shifts when the polar convection rolls system takes over within the transition zone at the latitudes where Icealnd is located.
Reykjanes Ridge Convection Rolls and Connection With Polar Convection Rolls
It must be remembered, that the main division line is actually 1.5° farther to the East, where the division between large lower mantle convection rolls is found.
The Reykjanes Ridge and Kolbeinsey Ridge form a rather regular division line between tectonic plates, south and north of Iceland. In between the pattern is more complex. As for the convection rolls below, they are in a way more complex under Iceland, due to the transit zone of polar and equatorial convection rolls.
The two systems meet at 64°N, and both are subject to the same mathematical formula. If we trace the Reykjanes Ridge Convection Rolls, we find this picture:
If the Reykjanes Ridge is supposed to have convection rolls at each side, then they can be extrapolated farther. The mantle is half molten and does not behave like the rigid surface. Therefore, the convection rolls must be continuous. Then, the same shape must prevail all the way.
Mid Atlantic Ridge Convection Rolls Division Line
The Mid Atlantic Ridge itself makes some side-jumps, and is swaying a bit irregularly. Still, the calculated convection rolls division line does cross the ridge itself at 32°N and at equator. This is something to think about, because the system is found to converge around 32°N, whereas the convection rolls there are oriented exactly north-south. At 0°, the fact that horizontal flow Coriolis effect shifts from right hand turn to left hand turn, explains the consistency of distance between main topographic features. In this case, the distance from center of Atlantic is exactly 30° to both S-America and Africa. That means of course, that the width from coast to coast of the Atlantic Ocean along equator is exactly 60°. Not strange, because each convection roll of lower mantle spans 30° from east to west.
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