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The Relative Tectonid Drift Between Africa and Eurasia

Steingrimur Thorbjarnarson

Looking at the modern GPS based map representing tectonic drift vectors, it looks like Africa and Eurasia are more and less drifting in a parallel way:

Looking at the Mediterranean and its surroundings, it is obvious that the African plate is being subducted below the Eurasian plate. The relative movement between those two plates consists therefore mainly of a northward component. The convergent boundaries are quite complex, as can be seen here:

This is a clip from the presentation found at: https://www.youtube.com/watch?v=cqK-CbuM3Eo (Geoscience Information for Teachers Workshop at EGU).

If we try to simplify this as much as possible, the two main features of the North Coast of Africa, and the Adriatic Sea should be looked at:

It is known that Italy has rotated and the Adriatic Sea has thereby been enclosed with slab reaching under both Italy and the Balkan Peninsula. The African Plate subducts below the Aegean Sea, Sicily and Turkey. Subduction from the north and the appearance of ocean floor due to spreading is omitted here. The lines resulting from the Convection Rolls Model can be seen, and of course the main purpose of this study is to compare that model with what is known about the geology of the area. For this short post, it is mainly pointed out that the North Coast of Africa coincides with the 32nd parallel where the convection rolls are aligned directly N-S. One aspect of that latitude is that two downwelling lines of two different layers coincide, and thereby also two upwelling lines of two layers coincide. This creates the opportunity for convergent boundaries to appear, if the downwelling part is the dominant factor (no-slip) and the upwelling part becomes neutral (slip). A consequence of this is that extension within the area is then mainly caused by the north component of drift of the Eurasian Tectonic Plate, as the subduction is mainly related to the conditions close to 32°N.

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The circular tectonic drift vectors of Anatolia

Steingrimur Thorbjarnarson

The tectonic drift of the Anatolian Plate is notably independent from its surroundings. While the Arabian Plate moves northward, similar to the African Plate, the Anatolian Plate exhibits a counterclockwise rotation. This motion can be examined through the lens of the convection rolls model to see whether it offers any additional insights. The outcome is striking and reveals two key points:

  1. The combined structure of convection rolls and plate boundaries appears to create the conditions for a central pivot point around which the Anatolian Plate rotates.
  2. If a fixed point within the convection model exerts a dominant influence on tectonic drift, then the convection rolls also offer a framework for understanding the subduction of the African Plate beneath the Eurasian Plate.

The map showing drift vectors can be found at:
https://www.tandfonline.com/doi/full/10.1080/19475705.2024.2446588#abstract

The most significant observation is that this central pivot lies near the 32nd parallel, precisely where two mantle upwelling lines intersect at approximately 32.1°E. Along this latitude, the convection roll system is aligned exactly north–south, making it a key structural feature, comparable in importance to the equator and the 64°N/S parallels. Interestingly, this location corresponds roughly to the eastern edge of the Nile River delta. It has previously been noted that the deltas of the world’s largest rivers—especially the Amazon at the equator—are situated at critical junctions within the convection rolls framework. https://magicmagma.com/2022/10/04/what-do-the-three-famous-rivers-amazon-nile-and-mississippi-have-in-common/

Given this fixed relationship between surface tectonics and mantle convection geometry, the concept of rollback requires reconsideration. In this case, the European continent appears to be drifting away from the latitude at which the African Plate subducts beneath it. Whether we interpret this as northward retreat of the African slab or northeastward drift of Europe, the geological consequences are functionally the same.

The side-view depiction of African Plate subduction shows how numerous geological features have developed over the last 35 million years, since subduction began. These reflect the continuing northeastward movement of the Eurasian Plate, while the northern edge of the African Plate descends beneath it.

This is from https://www.youtube.com/watch?v=cqK-CbuM3Eo

Just to clarify a bit what drives the tectonic drift anomaly of Anatolia, a particular bit of convection roll can be pointed out:

It can also be pointed out that most geothermal activity is found in this part of Turkey. Take a look at this map:

It is from https://www.researchgate.net/figure/Geothermal-map-of-Turkey-MTA-2021b_fig1_365230456

The red area in Western Turkey coincides with the convection roll taking part in driving the rotation of the local tectonic plate. This can explain the geothermal activity anomaly.

Note that the appearence of the aggregate of vectors of GPS drift measurements of the Anatolian Peninsula is not only circular, but also basicly from east to west. The mathematical precision of the drift can only be possible because of a very regular system of convection rolls underneath. The rolls following the drift are coupled to the layers above, the ones opposing are decoupled. Thereby the engine driving this interesting rotational drift of the plate can be explained thoroughly.

Just to clarify further how the convection rolls move the tectonic plate, this drawing is added:

The red areas provide force for the circle to move anti-clockwise in an almost circular way. As previously mentioned, the pivotal point is also a key point within the convection rolls system as a whole, due to the exact N-S alignment of convection rolls at the 32nd latitude.

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Katla Ice Cave in a wider context

Steingrimur Thorbjarnarson

A famous eruption occurred in 1918 of Katla Volcano in South Iceland and triggered the largest flood known on Earth in recent times. Today, a river flows through the area, called Múlakvísl. The very root of that river is originated from an ice cave, known as the Katla Ice Cave in the tourist industry. This is the opening of the cave:

The location of the glacial toungue of Kötlujökull can be studied on this map:

Looking closer at Kötlujökull, we find the location of the cave opening:

The most interesting sites are there for a reason. In the case of Kötlujökull, the inner forces meet with the outer forces of snow, ice and water flow. Here the similar conditions for shaping Barnafoss, Geysir and Hekla are mentioned. Barnafoss is shown here below:

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Can the Convection Rolls Model Help Identify Geothermal Resources?

Steingrimur Thorbjarnarson

Systematic measurement and compilation of data form the foundation of scientific work. However, over time, such efforts can also foster new perspectives on existing information—perspectives that may lead to fresh discoveries and innovation. Geothermal exploration relies on a range of data: knowledge of fractures, heat gradients, aquifers, thermal conductivity, surface water chemistry, and more. Based on this information, a well is drilled, and if conditions are favorable, hot water can be extracted from the ground.

The Convection Rolls Model offers an additional, indirect method to complement these approaches. By understanding tectonic drift vectors and recognizing that the boundaries between mantle convection rolls also influence divisions within the overlying tectonic plates, we gain a new framework for selecting promising geothermal sites. Iceland provides a compelling case study.

The map below shows the distribution of high- and low-temperature geothermal areas in Iceland. High-temperature zones are typically located near the boundaries of convection rolls, with a strong spatial correlation. In contrast, low-temperature zones tend to cluster within defined polygonal regions, also showing resemblance with the convection roll structure.

Map from Náttúrufræðistofnun Íslands, (Icelandic Institute of Natural History).

To identify new geothermal sites, a logical first step is to explore the intersections of convection roll boundary lines. Next, examining the distribution of known geothermal sites within the defined polygons may reveal consistent patterns — patterns that could guide the discovery of additional sites. However, this approach should be used in conjunction with established geological exploration methods to minimize the risk of error. The map, along with its scientific foundation, serves as a complementary tool to enhance the efficiency of land-based geothermal prospecting.

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Circular aspects of the Ring of Fire

Steingrimur Thorbjarnarson

Describing The Ring of Fire according to the map below, the San Andreas Fault and Yellowstone play the main roles. Accordingly, The Ring of Fire covers a rather wide area, mathematically confined. The San Andreas Fault has a section moving continually, as no pressure accumulates due to the fact that the drift direction of the Pacific Ocean Tectonic Plate is exactly parallel to the fault alignment. Just to add one fact, the sliding effect is due to the fact that the Pacific Plate drifts slightly away from the North American Plate at that point, but the North American Plate moves towards the point, so the combined result is a smooth, perpendicular meeting point. This is the most important thing to understand in an attempt to understand the preconditions of the Ring of Fire.

Yellowstone is therefore also a key point of the Ring of Fire. For a manifistation of that statement, we should have a look at a basic geological map of the Yellowstone Caldera:

Calderas tend to be regular, and therefore an elliptical form is used to aproximate the outlines of Yellowstone. Then the major and minor axis of the ellipse become apparent, and they are perpendicular and parallel, respectively, to the edge of the Ring of Fire at that location. The minor is aligned in the same way as San Andreas Fault. It is not necessary to add a detailed map of San Andreas Fault complex here, because everyone knows that it is logically parallel to the Ring of Fire.

Taking this a bit further, the Pacific Tectonic Plate drifts as a whole in one direction. On the contrary, the adjacent plates of America and Eurasia rotate towards the Pacific. The Ring of Fire also includes other plates than the Pacific Ocean Tectonic Plate, as it is defined. Other factors determine its scope too, and there we have the pattern shaped by convection rolls. The different layers of rolls have intersection points, coinciding with the outer and inner edges of the Ring of Fire. That provides the mathematical base for the elliptical form of the Ring of Fire. The way to realize this is simply to trace the two concentric yellow ellipses marking the Ring of Fire, and see how many intersection points each of them coincide with. The width of the Ring of Fire therefore always remains mathematically the same in proportion with the grid formed by latitudes and longitudes.

This description of the Ring of Fire is presently of a secondary nature, because first you have to have knowledge about the Mantle Convection Rolls Model, and then about the Ring and Fire and how it is related to the said model. Besides that, the tectonic drift vectors are not always presented as on the map above. A solid reference frame, and a view from space with GPS should describe tectonic drift in the best way. And it should be noticed that Yellowstone, according to this analysis, is a part of the Ring of Fire. More about this in my paper: https://pangea.stanford.edu/ERE/db/GeoConf/papers/SGW/2024/Thorbjarnarson.pdf