Author: Steingrimur Thorbjarnarson

Africa has a N-S structure, combined of the Nile and the Great Rift Valley complex. These two structures are connected at equator. The Great Rift Valley is often compared with Mid-Ocean Ridges, in the sense that if it would develop further, an ocean with a mid-ocean ridge in the middle, would eventually be formed. If we simplify these structures by drawing approximate N-S lines on a map (the 1977 World Ocean Floor Map created by Bruce Heezen and Marie Tharp), a curious pattern does emerge.

The structure fits into the pattern, slightly offset to the west if compared to the Mid-Indian Ridge. All the ridges sway a little, and the intervals are not perfectly regular. On the other hand, the intervals are regular enough to deserve attention. The ridges are all N-S oriented, the starting points of the N-S oriented sections are all found at equator, and the N-S sections are very close to being parallel to each other, separated by 90°.

Let us consider the possibility that a scientist, somehow curious about the structure of our planet, would look at the fourth N-S structure of 90° intervals. The said scientist would then find a main subduction zone, exactly at that location, found east of Australia, also mainly oriented N-S. Would our imaginary scientist keep on with the investigation? My wild guess is “yes”.

But somehow, some earth scientists would not continue with the investigation. They would refrain from it, because the regular distribution of mid-ocean ridges is contrary to the “gut feeling” that they should be randomly distributed. The precondition for that intuition is our moving picture of gradually drifting plates, where the ridges should continually shift location along with the plates. Thereby, most people will consider the possibility that the ridges had a different distribution in the past, and the distribution will be different in the future. Why should we then take the current distribution of mid-ocean ridges into account, when contemplating the science of Earth’s inner structure?

If this distribution is a coincidence, and we happen to live during the time of that coincidence, we still should be able to explain why this distributional regularity does “not count”. We can make some sort of an analogy to explain that. A clock has three needles, and we all know that the distribution is random, showing all types of patterns during a 12 hours cycle. Occationally, for instance at 12 o’clock, all the needles are unified. This happens literally only for a second, and then the random distribution of the needles becomes apparent again. So now we can ask ourselves, whether the distribution of those sections of mid-ocean ridges is of the same nature as when it is “12 o’clock”?

The answer is “no”, it would be too much of a coincidence. The solution to this problem is most likely that within the Earth a regular system of mantle convection is constantly moving the tectonic plates above, but at the same time the regularity of flow is manifested in some way or another. In a billion years, everything will have changed, but the system underneath will reveal itself, just as now.

Hope that this does clarify these things to some degree, as sometimes scientific findings can be explained much better with only a few extra words.

It is well known that land mass around equator is regularly distributed. The three mid-ocean ridges of the Pacific, Atlantic and Indian oceans are found to be aligned 90° apart, directly N-S, reaching southwards from equator a couple of thousand kilometers. Studying the N-S aligned volcanic zone of Northern Iceland, it is interesting to see that it is found directly north of the Mid-Atlantic Ridge of the Southern Hemisphere. The pattern of those three N-S aligned ridges therefore form an interesting pattern with Iceland included, far up north!

The drawing is superimposed on [Manuscript painting of Heezen-Tharp “World ocean floor” map by Berann]. https://www.loc.gov/item/2010586277/

How can these ridges be so regularly distributed, besides being found in context with the volcanic zones of Iceland? The answer is found in the convection rolls pattern formed by different layers withing the mantle. Together they form N-S oriented polygons, and the crust breaks in harmony with the resulting pattern. In many cases, though, ridges follow the division lines between convection rolls, and in some cases they follow other mathematical rules as well.

The fact, that the intervals between the parallel N-S sections span 90°, further adds to the feel of regularity. Each interval corresponds to the width of three convection rolls, each spanning 30° from east to west. To fully understand this, the whole system must be kept in mind, but this is a good beginning to consider what is going on.

Three mid-ocean ridges of the North Hemisphere, Juan de Fuca, Reykjanes Ridge and the Mid-Indian Ridge, are found to be mathematically correlated to each other. 1) Their alignment follows the same formula 2) The angle between Juan de Fuca and Reykjanes Ridge is 90°, and between Reykjanes Ridge and Mid-Indian Ridge is 93°. According to the Convection Rolls Model, a ridge following division line between convection roll will most likely be positioned 1.5° east or west of the main lower mantle convection rolls division line. The Reykjanes Ridge are found to be offset in opposite ways, Reykjanes Ridge being west of the line and the Mid-Indian Ridge east of the line, adding up to extra 3°.

Red lines indicate the location of the relevant ridges. The fact that the relationship is of double nature, angle and alignment, gives this model an explanatory value. The shape and location of convection rolls can be calculated very accurately, and thereby additional information can be gathered about conditions, tectonics and geological activity of any area on Earth.

This was introduced at the 48th Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, California, February 6-8, 2023.

December 15th 2022 an earthquake swarm appeared out of Langanes at Bakkaflóadjúp near the Northeast coast of Iceland. Some 40 years ago earthquakes were also measured there. The earthquakes occur exactly on the line for the main division between large scale convection rolls as they extend all the way from equator. Not many words are needed to explain this, just two simple drawings, one from the National Met Office, and one map with the main division drawn on it, map base from National Land Survey of Iceland.

There are actually two layers represented with this line, one is the eastern side of the convection roll which creates the Reykjanes Ridge. That convection roll is then subducted by the northern more rolls, so it is found at considreable depthe at these latitudes of the earthquake area. But the same is true for the large scale structures of the lower mantle, and effect from there are expected to take part in triggering these earthquakes. The large scale rolls intersect each other, the equatorial roll being subducted, and the lower mantle division line is therefore found near the boundary between mantle and core.

The three rivers estuaries are all 60° apart, coinciding with the convection rolls system. A river flows on the surface, so how does it connect with the mantle? The answar is that water is the best geologist. It always finds the weakest spots, wherever they are, in order to make a path to flow along. The annual isostatic fluctuation at these estuaries is of global geophysical scale, especially for Amazon with 8 cm vertical movement of the crust every year.

The convection rolls exist because heat must constantly leave the inner part of the Earth. It has been shown with experiments that mantle material heated so that it starts convecting, and not made accelerating any further than that, does form convection rolls. It is logical that exactly those conditions prevail inside the Earth. These rolls have to extend from equator and sway in a regular way. The weather system and the ocean current system form curved paths as they move along, and so does the mantle. The theory fits everywhere, no one can deny it. And here we have one more manefistation. The three estuaries are all 60° apart as compared with the relevant central point on the 32nd parallel, of a circular path revealing the division lines between the main convection rolls of the lower mantle. It is even so that Mississippi and Nile are very clearly 120° apart, because the estuaries happen to be very close to the critical 32nd parallel, one flowing from the north, the other from the south.

In the drawing, the main upwelling lines of large scale lower mantle rolls are shown, and the relevant backflow lines of horizontal flow. These black lines are only relevant for the upper mantle, and in a way also for the core. The effect of those lines is so big that they are responsible for the location of all those three rivers. Newly, BBC made a TV series about exactly these three rivers. They are very special.