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The Minor Axis of the Ring of Fire

Steingrimur Thorbjarnarson

Defining the exact boundaries of the Ring of Fire is not straightforward. However, it is increasingly recognized that the system exhibits an overall circular geometry, particularly when the volcanic regions of Antarctica are considered as part of the broader pattern. This observation deserves careful attention, and several key reference points can be used to define the geometry of the Ring of Fire.

The minor axis points of the Ring of Fire,Yellowstone,
San Andreas, Alpine Fault of New Zealnand and the Antarctican Plate.

The first and most widely recognized reference is the San Andreas Fault in California. Part of this fault aligns so closely with the inferred geometry that it undergoes continuous creep without generating significant earthquakes. For this reason, a representative point along the San Andreas Fault is selected as a reference point on the map.

On the opposite side of the Ring of Fire lies the Alpine Fault of New Zealand. Unlike the San Andreas Fault, the Alpine Fault is oriented approximately perpendicular to the adjacent margin of the Ring. This suggests that different tectonic adjustments occur along the line connecting these two major fault systems.

Additional features are found along the same axis. To the northeast lies the Yellowstone volcanic region, while to the southwest is the junction between the elliptical forms of the Pacific and Antarctic plates.

The idealized elliptical form of the Antarctic Plate,
showing the inferred connection point linking Antarctica to the Ring of Fire system.

The geometry of the Ring of Fire can then be completed by extending the circle so that it passes through two equatorial reference points: the eastern coast of Indonesia and the western coast of South America.

The resulting elliptical form is nearly symmetric about the equator. However, its center lies slightly south of the geographic equator, consistent with the position of the so-called tectonic equator.

As the Ring of Fire displays a remarkable correspondence with a number of geological features, suggesting that its position and geometry are not entirely coincidental but instead follow certain large-scale patterns, it is worthwhile to examine its structure in greater detail and attempt to explain its existence more thoroughly.

Previous sections have discussed the relationship between the equator and the subduction zones of eastern Indonesia and Peru. One of the first observations is the apparent correspondence between the Ring of Fire and the equatorial region. These two equatorial points are approximately 150° apart and, in this interpretation, define the outer limits of the Ring of Fire. The Ring itself extends somewhat beyond these points, which is reasonable given that the effects of subduction continue beyond the immediate trench systems. The Ring of Fire also exhibits relatively distinct inner and outer boundaries, making it useful to examine the inner boundary along the equator as well.

Both in Indonesia and Peru, connections can be identified between the outer and inner rings near the equatorial line. Along the northern coast of Papua New Guinea, several geological structures can be traced that follow this pattern. Similarly, west of Ecuador, the Galápagos Spreading Center extends across the eastern Pacific toward the Galápagos Islands, which in this model lie close to the inner boundary of the Ring of Fire. The Galápagos region is particularly noteworthy because it marks the interaction between oceanic spreading processes and the eastern margin of the Pacific subduction system.

A similar relationship can be identified along the minor axis of the Antarctic Plate ellipse. The outer ring intersects the northern extension of the minor axis, while the southern end is associated with the plate boundary system south of New Zealand. This boundary includes the Puysegur, Macquarie, and Hjort trench systems and connects northward through the Alpine Fault of New Zealand. The Alpine Fault shares some characteristics with the San Andreas Fault, although its orientation and tectonic setting are significantly different. The northern endpoint of the minor axis corresponds approximately to the region of Yellowstone in North America.

Attention should also be given to Japan. In this interpretation, the inner ring closely follows a major geological corridor extending from Hokkaido through Honshu to the vicinity of Mount Fuji. The major axis lies somewhat farther north and approaches the tectonic junction near Sakhalin Island. The outer ring approximately follows the transition zone between the highlands of western China and the lower-lying regions of eastern China. The inner ring also links the endpoints of the Kuril Islands, Kamchatka Peninsula, and the Aleutian Islands, which together form one of the most continuous volcanic arcs on Earth.

In South America, the ring encompasses the major volcanic chains of Peru and Chile, which are associated with subduction of the Nazca Plate beneath the South American continent. The resulting volcanic arc contains many of the highest active volcanoes on Earth. Likewise, most of the volcanoes of Antarctica fall within the two ellipses, including those of the West Antarctic Rift System and the volcanic provinces associated with Mount Erebus.

A substantial portion of the western Pacific subduction zones, however, lies outside the circular region defined by these ellipses. South of Japan, the Izu-Bonin Trench extends southward before curving into the Mariana Trench. The trench contains the Challenger Deep, the deepest known point in Earth’s oceans. Farther south, the Tonga Trench, Kermadec Trench, and Hikurangi Margin also lie inside the ellipses. These regions represent areas where convergent plate interactions are strongly influenced by the westward motion of the Pacific Plate relative to neighboring plates.

It is also interesting to observe how the Juan de Fuca Ridge terminates near the inner boundary of the Ring of Fire. From there southward toward Central America, a diverse range of tectonic boundaries—including spreading ridges, transform faults, and subduction zones—coincides with the inner ellipse. This transition illustrates the complexity of the northeastern Pacific margin, where different styles of plate interaction are concentrated within a relatively narrow geographical corridor.

Several additional observations support the significance of the Ring of Fire as a coherent tectonic system. Approximately 75% of the world’s active volcanoes and about 90% of global earthquakes occur along its margins. The Ring extends for roughly 40,000 km around the Pacific Ocean and represents the surface expression of a nearly continuous network of subduction zones and volcanic arcs. Although local plate interactions explain many individual features, the overall geometry of the system remains one of the most striking large-scale tectonic patterns on Earth, inviting further investigation into the deeper mantle processes that may influence its development.

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Eyjafjallajökull in a Global Context: Around the Earth

Steingrimur Thorbjarnarson

The volcanoes of Eyjafjallajökull and Katla are among the most famous volcanic systems in Iceland. They occupy a prominent position in the geology of South Iceland and have long attracted attention because of their apparent connection. Historically, eruptions of the two volcanoes have often occurred within relatively short intervals of one another, suggesting that some form of interaction may exist between the neighboring volcanic systems.

Eyjafjallajökull, an east-west aligned elliptical volcano,
with a glacial tongue flowing northward from the summit crater.
(https://www.visindavefur.is/svar.php?id=77035)

Geological maps reveal a remarkable east-west arrangement extending across the region. Katla lies beneath Mýrdalsjökull to the east, while Eyjafjallajökull forms an elongated volcanic edifice immediately to the west. The volcanic structures, fissure swarms, and associated tectonic features display a pronounced east-west alignment.

Eyjafjallajökull itself is an elliptical volcano. Its fissure swarm follows the long east-west axis of the edifice, indicating that the orientation is deeply rooted in the tectonic framework of the area. At the western end of this axis lies Seljalandsfoss, one of Iceland’s best-known waterfalls. At the eastern end, the glacier tongue of Kötlujökull marks the outlet area where meltwater and jökulhlaups from Katla most commonly emerge.

This eastern opening is particularly significant. When Katla erupts beneath its ice cover, large floods are generated. These floods frequently escape through the Kötlujökull outlet, effectively utilizing the same east-west corridor that connects Katla with Eyjafjallajökull. The repeated use of this pathway suggests that the axis represents a long-lived structural weakness within the crust.

Within the framework of the mantle convection rolls model, this east-west trend coincides with the central axis of a polygon formed by convection-roll division lines. In this interpretation, the geometry observed at the surface reflects deeper patterns within the mantle. The Eyjafjallajökull–Katla axis occupies the center of one such polygon, while other volcanic systems define its boundaries and corners.

Polygonal pattern formed by mantle convection roll division lines. According to the model, volcanic zones,
tectonic boundaries, and major geological features tend to develop along these persistent structural lines.

The north-south arrangement of volcanic centers is equally intriguing. Hekla occupies a prominent position to the north-east, while Vatnafjöll lies between Hekla and Eyjafjallajökull. Drawing a line through Hekla, Vatnafjöll, and the summit crater of Eyjafjallajökull reveals a clear north-south trend. According to the mantle convection rolls interpretation, this line represents another major axis of the same polygon.

The north-south axis and east-west axis through Eyjafjallajökull.

When viewed in a broader context, the north-south alignment does not end in South Iceland. Similar trends can be traced along the Mid-Atlantic Ridge, which itself forms one of the most prominent north-south geological structures on Earth. Extending the same geometric framework to a global scale, the trend can be followed toward the Southern Ocean and ultimately to the minor axis of the elliptical form of Antarctica identified elsewhere in this study, as seen here for example:

Location of Hekla (red circle) and the Elliptical Outline of the Continental Shelf of Iceland.

Whether examined locally or globally, Eyjafjallajökull and Katla occupy a unique position within Icelandic geology. Their historical relationship, their shared east-west structural alignment, the pathway of Katla’s jökulhlaups, and their position within larger tectonic patterns all point toward an underlying degree of geometric organization. The volcanoes are not merely neighboring volcanic systems; they appear to form part of a larger structural framework extending across Iceland and beyond.

Central Axis of Iceland Shelf and Eyjafjallajökull

The Eyjafjallajökull–Katla connection therefore provides an excellent example of how local volcanic features can be examined within a wider geodynamic context. The geological observations themselves are well established. The challenge is to understand whether these observations are isolated phenomena or components of a larger pattern linking Icelandic volcanism to the geometry of mantle processes on a planetary scale.

Geometric relationship between the elliptical Antarctic Plate, Iceland, and the Ring of Fire.
The minor axis of Antarctica aligns with Iceland to the north and, when extended southward,
coincides with the extrapolated minor axis of the Ring of Fire south of New Zealand.
The relationship becomes apparent on a South Pole-centered map
with the surrounding continents displayed on both sides of Antarctica.

The elliptical shape of the Antarctic Plate exhibits major and minor axes that are parallel to the corresponding axes identified in Iceland, particularly those associated with Eyjafjallajökull. Within the framework of the mantle convection rolls model, an apparent geometric connection can also be traced between Iceland and the Ring of Fire. The northern intersection of the Antarctic minor axis aligns with Iceland, while the opposite intersection point coincides with an extrapolation of the minor axis of the Ring of Fire south of New Zealand. This relationship can be examined by displaying world maps on both sides of a South Pole-centered projection, revealing the continuity of the large-scale geometric pattern.

.https://www.3develop.nl/blog/antarctic-projection-penguins-world-map/?utm_source=chatgpt.com

The continuity of the convection-roll pattern associated with the Mid-Atlantic Ridge and the subduction zones of the western Pacific can then be observed.

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South Iceland Seismic Zone — A Geometric Link Between Iceland’s Rift Systems

Steingrimur Thorbjarnarson

 Iceland Seismic Zone — A Geometric Link Between Iceland’s Rift Systems

The South Iceland Seismic Zone is one of the most remarkable tectonic regions in Iceland. It is not only a zone of frequent earthquakes, but also a key to understanding how stress, volcanic systems, and crustal deformation interact across the island. While the volcanic zones of Iceland often receive most public attention, the seismic zone between them reveals an equally important part of the tectonic structure.

The mantle convection rolls division lines polygon
framing the South Iceland Seismic Zone.

The zone stretches across southern Iceland, roughly between the western volcanic systems near Hengill and the eastern systems connected with Hekla and the East Volcanic Zone.

The hypothetical sequence of north-south aligned earthquake faults
superimposed on a map of the South Iceland Seismic Zone.

Unlike the volcanic rift zones, where extension is expressed through volcanism and fissure swarms, the South Iceland Seismic Zone mainly releases tectonic stress through earthquakes.

Mapped surface faults of SISZ
Simplified map showing earthquake and volcanic zones of Iceland.
Hekla

A Transform Zone Across Iceland

In plate tectonics, Iceland is usually described as a place where the Mid-Atlantic Ridge rises above sea level. The North American and Eurasian tectonic plates move apart across the island. However, the spreading is not expressed as one single continuous rift. Instead, the volcanic zones are offset from each other.

The South Iceland Seismic Zone acts as a transfer structure between these volcanic segments. In standard tectonic terminology, it is often described as a transform zone, although it differs from classical oceanic transforms because deformation is distributed across a broad area rather than concentrated along one fault.

The earthquakes of the zone commonly occur on north-south oriented faults, even though the broader tectonic movement across Iceland is mainly east-west extension. This apparent contradiction is one of the most interesting aspects of the region.

The Diamond-Shaped Geometry

One of the clearest large-scale geometric features of the seismic zone is its tendency toward polygonal organization. The region can be interpreted as a broad diamond-shaped area between volcanic systems.

The eastern and western ends connect naturally with major volcanic centers, to the west: the Hveragerði geothermal region, and to the east at Hekla and the western margin of the East Volcanic Zone

Within this framework, stress appears to organize itself along lines that connect opposite corners of the polygonal area. The result is the repeated formation of north-south fracture structures inside an overall east-west tectonic setting.

This is one reason why the South Iceland Seismic Zone is so important geologically. It demonstrates that tectonic deformation is not simply linear. Instead, it becomes organized into geometric structures where local stress fields redirect movement into highly regular patterns.

Earthquakes and Historical Activity

The South Iceland Seismic Zone has produced many destructive earthquakes throughout Icelandic history. Some of the strongest historical earthquake sequences occurred in this region, affecting farms, churches, and settlements across the lowlands.

Notable earthquake episodes include:

  • The great earthquakes of 1784
  • The 1896 earthquake sequence
  • The June 2000 earthquakes
  • The May 2008 earthquakes

5

The earthquakes are usually shallow, which increases their impact at the surface. Even moderate earthquakes can therefore produce significant shaking.

Connection With Hekla

Hekla occupies a uniquely important tectonic position at the eastern end of the seismic zone. It lies where several tectonic tendencies intersect:

  • Connecting the South Iceland Seismic Zone and the East Volcanic Zone
  • A key function within the regional spreading across Iceland
  • Direct north-south structural alignments

Because of this, Hekla can be viewed as both a volcanic center and a tectonic focal point.

The geometry becomes especially interesting when Iceland is examined together with its continental shelf and offshore ridge systems. The South Iceland Seismic Zone appears not merely as a local fracture belt, but as part of a broader structural organization extending into the North Atlantic.

A Broader Geometric Interpretation

The South Iceland Seismic Zone also provides an opportunity to examine tectonics through geometric relationships.

The repeated north-south fracture orientation inside a broader east-west tectonic environment suggests that deformation is influenced by organized stress fields rather than random faulting alone. Similar geometric tendencies can be observed elsewhere in Iceland, particularly where polygonal crustal blocks form between volcanic systems and fracture zones.

In the mantle convection rolls interpretation, these polygonal structures emerge naturally from the division lines between adjacent convection cells. Pressure along the sides of such polygons can produce fracture systems that connect one corner to another, generating north-south alignments within larger east-west tectonic regions.

Whether examined through conventional tectonics or broader geometric models, the South Iceland Seismic Zone remains one of Iceland’s clearest examples of how crustal deformation organizes itself into remarkably regular patterns.

A Geological Laboratory

Few places on Earth allow such direct observation of active tectonics as Iceland. In the South Iceland Seismic Zone, earthquakes, volcanic systems, geothermal areas, and visible surface fractures all interact within a relatively compact area.

The landscape of southern Iceland preserves these processes in extraordinary clarity. Every earthquake sequence adds another chapter to the evolving tectonic story of Iceland.

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Hawaii at the Center of the Global Tectonic Pattern

Steingrimur Thorbjarnarson

It is well known that the African Tectonic Plate has been drifting relatively slowly compared with many of the surrounding plates. On the opposite side of the globe, the Pacific Plate also appears exceptional in several respects. At its center lies Hawaii, one of the most volcanically active regions on Earth.

Theoretic Pacific-centered tectonic map emphasizing the approximately equal spacing
of the Mid-Atlantic Ridge and Mid-Indian Ridge relative to Hawaii.

The S-shaped red lines show the location of the divisions, according to the mantle convection rolls model, associated with the minor and major axes of Antarctica. When the globe is viewed from a Pacific-centered perspective, with Hawaii near the middle of the map, an interesting geometric relationship appears. The theoretical central axes of the Mid-Atlantic Ridge and the Mid-Indian Ridge lie at equal distances from Hawaii. This relationship can best be illustrated with a world map centered on the Pacific Ocean.

In such a representation, the three major mid-ocean ridge systems — the Mid-Atlantic Ridge, the Mid-Indian Ridge, and the East Pacific Rise — together with the principal subduction zones of the western Pacific, appear geometrically connected with the endpoints of the major and minor axes of the elliptical form associated with the Antarctic Tectonic Plate.

Within this framework, Hawaii occupies a particularly central position. It lies midway between the axial region of the Pacific spreading system, represented by the East Pacific Rise, and the extensive subduction systems of the western Pacific Ring of Fire. Seen in this way, Hawaii becomes part of a broader large-scale geometric arrangement linking the Pacific basin, Antarctica, and the global mid-ocean ridge network.

This concept can be illustrated effectively with a Pacific-centered world map, where Africa appears on both outer edges of the projection, emphasizing the symmetry and large-scale relationships of the global tectonic system.

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The Function of Indonesia’s Subduction Zones and the Caribbean Subduction and Transform Zones within the Ring of Fire

Steingrimur Thorbjarnarson

Comparing the geometry of Indonesia and the Caribbean reveals a remarkable degree of similarity. Although these two tectonic systems are located on opposite sides of the Pacific realm, many of their large-scale structural relationships appear comparable.

The Identical Shape of Indonesia and the Caribbean:
Comparable Subduction and Transform Geometry on Opposite Sides of the Ring of Fire

First, both systems are closely associated with the equatorial region. The Indonesian arc faces southward, with one important eastern endpoint located near the coast of Sumatra. Another major subduction-related crossing appears roughly 30° farther east along the equatorial zone, connected with the subduction framework surrounding the Philippine Plate.

A similar arrangement can be observed in the Caribbean region, although shifted slightly north of the equator. The Caribbean basin is associated with another pair of crossings of lower-mantle flow structures, where subduction-related zones occur at points approximately 30° apart, comparable to the Indonesian case. The Caribbean arc also extends outward in a manner resembling the Indonesian arc.

The Central American Trench stretches from the inner part of the Ring of Fire toward its outer margin, where the division line appears to turn toward the key region of the Peru–Chile Trench near the equatorial framework. This geometry resembles the relationship between the New Guinea Trench and the continuation of the Philippine Trench on the Indonesian side of the Pacific.

In this way, many aspects of the Indonesian and Caribbean plate-boundary systems appear strikingly similar, although effectively rotated by 180° relative to one another.

Considering that these two tectonic regions connect the Pacific Ocean with the Indian Ocean and the Atlantic Ocean respectively, the broader function of this arrangement becomes important to examine. The fundamental span of a 30° convection-roll unit, together with an additional extension east of the eastern crossing points, may help explain the tectonic importance of these paired regions on opposite sides of the Ring of Fire.

South of Indonesia, subduction is the dominant tectonic process, whereas in the Caribbean region transform motion and tectonic transition play a larger role, especially along the northern boundary of the Caribbean Plate. Even so, both systems appear to participate in a broader structural unity within the Ring of Fire.

The anticlockwise rotational tendency associated with the North American sector of the Ring of Fire is consistent with the northward-facing curvature of the Caribbean arc and the southward-facing curvature of the Indonesian arc. At the same time, the long-term expansion of the Atlantic Ocean on one side and the Indian Ocean on the other appears to be buffered near equatorial latitudes by these major subduction and transform systems situated between the large ocean basins.

The similarities are therefore sufficiently striking that they may partly reflect an underlying large-scale geometric organization. At the same time, this comparison leaves many important questions unanswered and suggests several directions worthy of further investigation. Further information: https://pangea.stanford.edu/ERE/db/GeoConf/papers/SGW/2024/Thorbjarnarson.pdf

All of these characteristics of the two archipelagic systems are, of course, well known. They can first be summarized as follows:

  1. Both archipelagos are associated with the Ring of Fire.
  2. Both archipelagos are located close to the equator.
  3. Both archipelagos have a predominantly east–west orientation.

However, when compared within the framework of the mantle convection rolls model, several additional observations can be made:

  1. When the tectonic features of Central America are included, the overall mathematical framework becomes directly comparable to that of Indonesia.
  2. The width of both archipelagic systems is comparable when measured in degrees of longitude along their respective latitudes.
  3. The relative position of both archipelagos appears comparable in the context of the large-scale convection-roll geometry proposed in the mantle convection rolls model.