Tag: nature

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Convection Rolls and the Global Logic of Plate Tectonics

Steingrimur Thorbjarnarson

The surface of our planet bears the unmistakable marks of forces that operate deep within its interior. Mountains, rift valleys, volcanic arcs, and ocean basins are not random accidents of nature but the result of systematic and persistent geological processes. Among these, the concept of mantle convection, where heat from Earth’s interior drives circulating rolls of plastic mantle, offers a coherent way to understand the global distribution of geological features. When we examine the Atlantic Ocean, the Pacific Ring of Fire, and particularly Iceland’s unique geology, we can see a consistent pattern that points to convection rolls as a guiding force in shaping the planet’s surface.

The Mid-Atlantic Ridge: A Symmetrical Rift

The Mid-Atlantic Ridge is one of the most striking linear features on Earth. Stretching north to south, it runs down the center of the Atlantic Ocean like a seam on a baseball. Along this ridge, tectonic plates are moving apart, and new crust is being created as magma rises to fill the gap. What is remarkable is the symmetry of this system. The forces that shape the eastern Atlantic margins, along Europe and Africa, are mirrored in the geological structures along the western margins, facing the Americas.

This symmetry suggests that the same deep mantle processes operate beneath both sides of the Atlantic. The ridge itself acts as the surface expression of an underlying upwelling zone, hot material rising in a systematic manner from below. The spreading, volcanism, and earthquakes observed along the Mid-Atlantic Ridge are thus not isolated features but the predictable result of convection-driven divergence.

To fully comprehend the effect of convection rolls, it is important to recognize that Earth’s interior is not a single uniform system but a set of layers, each with its own convection dynamics. Convection rolls in different layers may be oriented in different directions, creating complex interactions between them. On top of this, the large-scale convection rolls of the lower mantle are often overlain by smaller rolls in the upper mantle and asthenosphere. These smaller rolls add detail and local variation to the broader global pattern. As a result, surface expressions such as mid-ocean ridges appear at once holistic, reflecting the influence of large-scale mantle circulation, and discontinuous, because smaller-scale convection rolls introduce irregularities and segmentation. This layered and multi-scale system helps explain why Earth’s geological features can seem both systematic and fragmented at the same time.

The Pacific Ring of Fire: A Continuous Arc

Moving to the Pacific, we encounter an entirely different yet equally systematic phenomenon: the Ring of Fire. This chain of volcanoes and seismic zones encircles the Pacific Ocean, from the Andes in South America, up through North America’s Cascades, across the Aleutians, and down through Japan, the Philippines, and New Zealand.

At first glance, the Ring of Fire may seem irregular, since the volcanoes and trenches occur in different geological settings. Yet when viewed through the lens of mantle convection, it becomes clear that similar forces are at work around the entire Pacific rim. Subduction zones, where one plate dives beneath another, are surface expressions of downwelling limbs of convection rolls. The arcs of volcanoes, aligned in systematic chains, form where mantle material melts and rises due to the descending slabs. Just as the Mid-Atlantic Ridge reflects upwelling, the Ring of Fire reflects downwelling and lateral flow. Both belong to the same fundamental system.

Convection Rolls as a Global Framework

The systematic appearance of these geological features, ridge in the Atlantic, arcs around the Pacific, points strongly toward convection rolls as the underlying framework. Instead of imagining Earth’s mantle as chaotic or localized in its motions, we can view it as a series of organized rolls, like giant conveyor belts. These rolls transport heat from the deep interior to the surface, and in the process, they drag along the tectonic plates. It is important to point out that the rolls working against the drift of the plates above tend to be neutral due to slip effect, and the rolls acting in the same direction accelerate or maintain the drift due to no-slip effect. This horizontal drift can only be maintained with ridges and subduction zones, which in turn fit into the pattern of the convection rolls system.

By adopting this perspective, the global distribution of active regions becomes much more comprehensible. Features that might otherwise appear disconnected, the Andes, the East Pacific Rise, the Aleutians, or the Mid-Atlantic Ridge, can be seen as parts of the same coherent system.

Iceland: A Natural Laboratory

Among all the regions where convection manifests at the surface, Iceland stands out as one of the most revealing. Straddling the Mid-Atlantic Ridge, Iceland is literally being pulled apart by the diverging North American and Eurasian plates. The island is intensely volcanic, with eruptions occurring regularly, and geothermal energy bubbling up in hot springs and geysers.

What makes Iceland particularly interesting is the systematic pattern observable in its geology. Studies reveal repeated occurrences of features at roughly 1.5° intervals from east to west. These intervals are not random. They suggest that convection rolls beneath Iceland influence where magma rises and where fissures open. Instead of a single point source or isolated plume, Iceland’s structure implies a rolling system of upwellings and downwellings, each spaced in a consistent rhythm.

This pattern is like a fingerprint of convection rolls imprinted directly onto the surface. It provides one of the clearest local examples of how mantle dynamics can create systematic geological structures.

Extrapolation to Global Geology

If such a system can be identified beneath Iceland, it is logical to extend the same reasoning to other parts of the world. Iceland is not unique in experiencing volcanism or tectonic spreading. It is simply an especially visible case because the ridge rises above sea level there. The same processes occur all along the Mid-Atlantic Ridge, hidden under the ocean. Likewise, the arcs and trenches of the Pacific reveal similar spacing and repetition when studied carefully.

By extrapolating the system of convection rolls outward, one can explain the arrangement of many other active geological areas worldwide. The Mediterranean volcanism, the East African Rift, the Philippine arcs, and even intraplate hotspots may be understood within the same framework. They all represent surface manifestations of a deeper and more systematic circulation of Earth’s mantle.

A Unified Perspective

The strength of this convection-roll model lies in its ability to unify diverse geological observations into a coherent picture. Rather than treating each volcanic chain, rift, or trench as a separate phenomenon requiring a unique explanation, we can see them as interconnected parts of a global circulation system.

In the Atlantic, this system explains the symmetry of spreading ridges. In the Pacific, it accounts for the continuous arc of subduction and volcanism. In Iceland, it reveals itself in the regular spacing of geological features. On a global scale, it provides a logical framework for understanding why geologically active regions appear where they do.

Conclusion

The Earth’s surface is a complex mosaic of geological features, but beneath that complexity lies order. The Mid-Atlantic Ridge’s north–south orientation, the continuous Ring of Fire around the Pacific, and the repeated spacing of structures in Iceland all point toward the same conclusion: convection rolls in the mantle are shaping our planet in a systematic way. By recognizing this pattern and extrapolating it globally, we gain not only a deeper understanding of Earth’s past but also a predictive framework for studying its geological future.

The study of Earth’s interior is far from complete, but each new observation strengthens the view that mantle convection is not a chaotic process but an organized system of rolls. These rolls, moving slowly over millions of years, have carved the face of the planet, lifted mountains, opened oceans, and lit volcanic arcs. From the symmetry of the Atlantic to the fiery arcs of the Pacific, and from the rhythmic geology of Iceland to the restless rifts of Africa, the logic of convection rolls offers a powerful lens through which to read the Earth’s grand design.

Geysir: The most famous geological feature of Iceland.
The wide red line represents large scale lower mantle divisions. Geysir is found just at its side,
but exactly on a division line between smaller convection rolls.

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The Ring of Fire is Circular for a Reason

Steingrimur Thorbjarnarson

The Ring of Fire is in fact circular, and 15 main parts of it are pointed out on the map below. The shape of the Ring of Fire is indeed circular, because the volcanoes of Antarctica fit into the area in between two elliptical shapes drawn with its outer limits marked by two points on equator, at the coast of Indonesia and South America, respectively. The two points are characterized by subduction zones. Let us examine this most active area in the World, in terms of seismic and volcanic activity. Looking at the arrows and lines, it is easy to understand how reality fits with the model.

  1. The first point pointed out on the map is the subduction zone of the Philippian Plate at the coast of Indonesia. It is a triple point where both the Philippian Plate and Pacific Plate meet with Indonesia. The South American counterpart on the equator is found exactly 150° west of this point. It fits to the width of five large-scale convection rolls.
  2. The Challenger Deep is the lowest point on Earth. It coincides with the inner margin of the Ring of Fire as drawn here. The convection rolls of different layers coincide with the area.
  3. Honshu Island of Japan clearly coincides with the convection rolls model, and is also within the elliptical area of the Ring of Fire.
  4. Kamchatka has been examined in other posts here, and the volcanic zone follows the alignment of convection rolls. It falls into the elliptical zone in similar way as Honshu Island.
  5. The Aleutian Islands form an arc from east to west. The easternmost part seems to follow the path of a division line between convection rolls. The central part crosses a large-scale convection roll, and the western part connects with Kamchatka. This arrangement indicates why most areas fall within the form of two ellipses, with short segments originated from convection rolls division lines.
  6. Cascadia is mentioned in two of the main articles found on this site. Subduction and divergent boundaries are found in the area.
  7. The Yellowstone National Pard is specially interesting, because usually it is not mentioned as a part of the Ring of Fire. As presented here, it is strongly related to it in two different ways. First, it is found on the circular line connecting the two points on equator. Second, it is found on the straight line of the mathematical minor of the elliptical forms, in continuation of the Central San Andreas Fault. New Zealand is on the other side of the Ring of Fire, where the other end of the said minor is found. With a little bit of logic at hand, it is then possible to analyze what kind of stress point this is, and thereby what causes the extraordinary activity level of Yellowstone Park. The usual saying, that it is a hot spot, is not enough. Of course it is a hot spot. But the settings of the Ring of Fire do indicate a complex origin of the volcanic and geothermal activity found there.
  8. The San Andreas Fault is found on the inner margin of the Ring of Fire and is used here to find that inner margin. The inner elliptical shape is not as clearly marked as the outer ring found by intersecting two obvious points on equator.
  9. Central America has some interesting features, especially volcanic activity where petrological evidence can be used to examine the explanatory value of the convection rolls model.
  10. This point has already been mentioned as the counterpart of point 1.
  11. The Galapagos Islands are found on equator in between the elliptical forms of the Ring of Fire.
  12. The Andean Mountains fit very well to both Convection Rolls Model, and the modelled Ring of Fire.
  13. The volcanoes of Antarctica are more seldom mentioned in geological literature than many others, but they are of course just as important for geological studies. The location of those volcanoes fits exactly into the circle. It indicates that the circularity is actually a precondition of the subduction zones system.
  14. New Zealand has been mentioned as a counterpart of San Andreas and Yellowstone, being on the mathematical minor of the circle.
  15.  The Australian Mountains are not mentioned as a part of the Ring of Fire, but they are found within its realms, and it is said that they are still gradually growing higher.

In this way, it can be explained that the Ring of Fire is a wholistic area. It is correct to describe it as a ring, and should be studied more extensively .

The circular form of the Ring of Fire.

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The Ring of Fire on Equirectangular Map

Steingrimur Thorbjarnarson

Drawing the Ring of Fire on an equirectangular map, the main features fall into a narrow zone.

Two of the areas named on this map are often omitted when analysing the Ring of Fire, namely Yellowstone and Antarctica. With Antarctica included, the name ‘Ring of Fire’ can be taken literally, as a whole elliptical form is completed. Following up on this point, the circle is remarkably regular, with symmetric features, such as New Zealand, San Andreas Central Fault and Yellowstone on the minor axis. To be more precise, the San Andreas Fault is found where the inner ring crosses the minor axis, and Yellowstone is located where the outer ring crosses the same axis.

The basic idea by drawing the circle in this way, is the fact that subduction takes place exactly where equator crosses the outer ring within the Philippean Trench at the coast of Indonesia , and the Peru-Chile Trench crosses the same ring also on the equatorial line.

With a more detailed analysis, it can also be shown how the two rings follow the division lines drawn, representing the model introduced here. Examining the subduction zones one by one, a striking consistency between division lines and subduction zones is found.

Considerable research has been carried out regarding the subduction zones, and I like the work of Robert J. Stern a lot, as he has not only carried out a lot of measurements, but also contributed to the study of Earth’s history. Please read his article about the origin of subduction zones: https://speakingofgeoscience.org/2013/04/28/when-did-plate-tectonics-begin-on-earth-and-what-came-before/

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Volcanic Activity near Grindavík on the Reykjanes Peninsula

Steingrimur Thorbjarnarson

The volcanic activity near Grindavík can be explained by referring to the interaction between a dyke forming within the volcanic zone, and magma from the dyke finding its way to the surface through earthquake faults. A seismic zone creats a weakness of the crust within the area. The orientation of the dyke is quite different from that of the earthquake faults. According to calculations the dyke is oriented about N43°E, and the earthquake faults trend is directly N-S. Real circumstances are not quite so simple, because the upper most manifestations of earthquake faults are en échelon arranged, divided into smaller systems with NE-SW trend. The dyke, when meeting with the earthquake faults, also bends, or follows the N-S trend near the eruption site. As I have been exploring the possibility that convection rolls are found withn the asthenosphere, and mapping the division lines between them, it is interesting to compare those lines with the conditions at the eruption site. Two downwelling lines of the lower parts of the asthenosphere are found directly below the eruption site itself. To understand the situation better, we should have a look at a map showing this:

This shows how the black division line crosses the Reykjanes Seismic Zone shown with red parallel lines. It is tempting to assume that the origin of magma can be traced to those two division lines directly below the eruption site. Another possibility is that the magma is originated from the upper most division line, alinged NE-SW, found slightly west of the eruption site, flowing at first under the crust along the NW-SE aligned line until it reaches the eruption site area. Then it ascends into magma chambers and finally to the surface.

This site shows many different situations where convection rolls system and real circumstances fit together. This is of course a very good example. The fact that the three eruptions along the dyke which formed under Fagradalsfjall, and the four eruption that have already taken place along the dyke forming at the side of Sundshnúkur have the same petrological origin is consistent with this.

This is an explanation built on many years of research. I have taken part in a series of conferences and meetings, publishing papers where the scientific papers pointing in this direction are cited. I also took part in mapping the South Iceland Seismic Zone, giving me the feeling of how the seismic area of Reykjanes works, as those two systems are connected end-to-end.

To explain the heat flow within the Earth, from radioactivity to eruption, is not easy, but it can be done. This eruption deserves much attention, and among the countless examples shown here, this one of those literally to the point.

The two other seismic zones of West Iceland (BTZ) and South Iceland (SISZ) are added to show how likely it is that the polygons surrounding distinct areas of Iceland really exist. To form a seismic area, pressure is nedded. The faults are all N-S oriented, so regularity is needed. The parallel faults are found side by side in E-W direction, having distinct endpoints, so the area is limited. The only solution for an outer framework is a polygon, exactly as drawn on the map here above. The division lines between convection rolls coincide with this enevitable polygonal shape surrounding the seismic zones. Therefore, it makes sense that the division lines are responsible for shaping the polygons in the first place. It is all about logic.