The 65th parallel, extending from the Snæfellsnes Volcanic Belt eastward to Snæfell and the surrounding region, is here divided into three equal segments.
Volcanic systems of Iceland, with convection rolls grid superimposed and symmetric areas identified.
The western segment, referred to as the Snæfellsnes window, extends eastward to Reykholtsdalur, an area notable for hosting Deildartunguhver, the most powerful hot spring in the world, with a natural discharge of approximately 180 liters per second of boiling water. The second segment, equal in size, spans the region between Reykholtsdalur and the western boundary of the East Volcanic Zone. The third segment includes Snæfell and its surrounding volcanic features. Notably, this eastern window occupies a position that is geometrically mirrored relative to the Snæfellsnes window when evaluated within the defined division framework. The locations of Hekla and Eyjafjallajökull further illustrate the symmetry inherent in this configuration.
The motivation for emphasizing this observation lies in a particularly robust spatial constraint: Snæfellsjökull and Snæfell are located at exactly the same latitude. In addition, both volcanic centers are positioned at equal distances from Hekla volcano and its north–south–oriented axis. This coincidence is independent of any applied rotation and therefore represents an objective geometric relationship rather than a constructed one. Furthermore, when mirrored, both volcanic centers align with the same division-line grid, suggesting that their placement within their respective volcanic belts is not arbitrary.
Snæfell is geologically separated from the East Volcanic Zone (EVZ), as it belongs to the Öræfajökull Volcanic Belt. Nevertheless, the Snæfellsnes Volcanic Belt and the corresponding section of the EVZ are compared here as structural counterparts within this geometric framework. In addition, the Langjökull volcanic systems within the West Volcanic Zone and the Hofsjökull system within the Mid-Iceland Volcanic Belt—represented here by a single polygon—can be compared using identical window dimensions centered on the north–south axis defined by Eyjafjallajökull and Hekla.
At this latitude, five volcanic zones are intersected, all of which conform to the convection-roll division lines as outlined here. The 65th parallel is also of particular importance because it coincides with a regional transition from predominantly NE–SW-oriented volcanic and fissure systems to a primarily N–S orientation.
Although geometric similarity alone cannot establish causation, the degree of correspondence observed in this analysis supports the internal consistency of a model based on geophysically constrained layer thicknesses within the Earth and the physics of mantle convection. In particular, these observations are consistent with the hypothesis that mantle convection rolls, together with the associated regional stress-field symmetry, exert a first-order control on the spatial organization of volcanic zones in Iceland.
The two parallel volcanic regions of Iceland—the Reykjanes Ridge together with the Reykjanes Oblique Rift Zone and the West Volcanic Zone—form a continuous tectonic structure. A second, parallel structure is found approximately 1.5° farther east and consists of the Vestmannaeyjar (Westman Islands), the South Iceland Volcanic Belt, and the East Volcanic Zone. These two volcanic lineaments are compared here.
Volcanic systems and grid of convection rolls division linesComparison of western and eastern volcanic systems
The parallel geometry of the two structures is discussed, followed by a closer look at their internal details. The western set of volcanic systems is divided into polygons 1A–6A, while the eastern set is divided into polygons 1B–6B.
Comparison of individual polygons
1A and 1B: Polygon 1A represents the northern end of the Reykjanes Ridge before it turns westward. Polygon 1B contains the Vestmannaeyjar volcanic system.
2A and 2B: Polygon 2A still represents the Reykjanes Ridge and includes the first volcanic systems on the Reykjanes Peninsula. Polygon 2B contains Eyjafjallajökull, Katla, and several additional volcanic centers of the South Iceland Volcanic Belt.
3A and 3B: Polygon 3A contains numerous volcanic systems arranged in a clear en echelon pattern. The westernmost system is Hengill, which extends into polygon 4A. The combined active areas of polygons 3A and 3B span approximately 1.5° in an east–west direction. The Grímsvötn volcanic system extends into polygon 3B and then turns sharply southward into the next polygon.
4A and 4B: Polygon 4A contains two volcanic systems, both located in the western half of the polygon. A structural shift is evident here: instead of the Reykjanes Ridge being aligned along the western boundary of the polygon set, the volcanic systems are now aligned along the eastern boundary. Þingvellir National Park lies near the center of this polygon and is commonly interpreted as a clear expression of plate divergence. In contrast, polygon 4B is almost completely filled with volcanic systems, dominated by the Grímsvötn and Bárðarbunga systems.
5A and 5B: Polygon 5A is dominated by Langjökull and its associated volcanic systems. These systems occupy a wider zone than those in polygon 4A but are still concentrated toward the western side of the polygon. Polygon 5B is again densely populated with volcanic systems, including Grímsvötn in the south, Kverkfjöll in the east, and Bárðarbunga near the center.
6A and 6B: Polygons 6A and 6B belong to the two parallel volcanic belts, but in both cases the tectonic alignment of fissures and volcanic systems changes at this latitude. North of polygon 6A lies the extinct Skagafjörður volcanic zone, which is not shown on the map because volcanic activity ceased there several hundred thousand years ago. Polygon 6B marks the onset of the North Volcanic Zone, which is aligned directly northward.
Interpretation
The observed geometry and continuity of these volcanic belts can be explained by the presence of long-lived mantle convection rolls beneath Iceland. The two parallel A and B polygon sets are connected by a transitional region, often referred to as the Mid-Iceland Belt. Examination of the details shows that the division lines correspond closely to the southern and northern limits of volcanic activity within this region.
This framework provides a clearer understanding of volcanic activity in Iceland. The two parallel volcanic structures are particularly well suited for analysis and interpretation. The next step is to examine the remaining volcanic zones, including Snæfellsnes, Öræfajökull, North Iceland, and Grímsey.
Dividing the Ring of Fire into eight approximately equal sections reveals a remarkable symmetry.
Cascadia and western Canada, extending southward to the San Andreas Fault.
California and the Middle America Trench.
The Nazca Plate and the Peru–Chile Trench.
The main volcanic region of Antarctica.
The section containing Mount Erebus.
An exceptional segment, where most tectonic and volcanic activity occurs inside the outer elliptical structure. This includes the Tonga–Kermadec Arc, with New Zealand located on the minor axis between sections 5 and 6.
The Philippine Plate, where the eastern plate boundary extends beyond the inner ellipse.
The island arcs of the Aleutian and Kuril Islands. Japan lies near the major axis, while the Hawaiian Islands extend outward from the north–south axis of the elliptical structure.
The outer ellipse is defined by connecting equatorial trench locations at the coasts of Indonesia and South America, specifically the Philippine Trench and the Peru–Chile Trench.
The origin of this horizontally oriented elliptical geometry is not immediately obvious; however, the San Andreas Fault represents a key constraint. Along this fault, motion is smooth and continuous where the minor axis intersects the inner ellipse, reflecting a kinematic balance between the westward drift of the North American continent and the motion of the Pacific Plate.
This geometric framework also incorporates Yellowstone, which lies at the outer intersection of the minor axis, with New Zealand forming its opposing counterpart.
Earth’s rotation is clearly a primary factor in shaping these large-scale patterns. The geometry can also be meaningfully compared with the convection-rolls model, suggesting a deeper, organized structure beneath the observed surface tectonics.
Here is my essay about the Ring of Fire for further reading:
Visualizing mantle convection rolls becomes significantly easier with the use of AI-based three-dimensional models. What were once abstract concepts—difficult to imagine and even harder to communicate—can now be rendered as coherent flow structures extending through the mantle. These visualizations provide an important bridge between mathematical models of mantle dynamics and the geological features observed at Earth’s surface. Here is a beginning:
AI-made simplified version of convection rolls under Iceland.
Understanding mantle convection is essential if we are to understand nature correctly. When long-lived convection rolls are taken into account, the spatial distribution of volcanism, rift zones, and seismic belts becomes more intelligible. Location of volcanoes and earthquake zones can be explained, and mid-ocean ridges are not randomly distributed features; instead, they align along sections that can be calculated, and notably, the same mathematical framework can be used to trace subduction zones.
Iceland is exceptionally well suited for testing this type of model. Few regions on Earth display such a concentration of geological features within such a limited area. This makes it possible to compare predicted mantle-flow patterns directly with mapped surface expressions. AI-generated 3D visualizations allow these comparisons to be made more intuitively, helping to explain how the geometry of convection rolls corresponds to volcanic zones and rift systems.
The functioning of mantle convection rolls is not immediately intuitive and requires time to grasp. The mantle behaves neither as a simple liquid nor as a rigid solid. Instead, temperatures are close to the solidus, allowing slow but organized flow to take place over geological timescales. Molten magma—which may eventually erupt as lava at the surface—is originally supplied along the division lines between adjacent convection rolls, where hot mantle undergoes partial melting and ascends through the tectonic plate.
A model showing correct proportions of the convection rolls along 64°N.
These rolls exert a direct influence on the tectonic plates above them. Through basal traction, the organized mantle flow causes tectonic drift. In most cases, the direction of mantle flow reinforces the dominant tectonic drift. However, in certain regions, a smaller convection roll may locally oppose the main trend of plate motion. When this occurs, extensional stresses can develop in the overlying crust, leading to rifting.
Such rifting is not merely conceptual but measurable. Over time, an active rift zone does typically span 1.5 degrees from east to west. The East Volcanic Zone in Iceland provides a clear example. Its width, orientation, and volcanic productivity are consistent with localized interaction between mantle convection rolls.
By combining mathematical descriptions of mantle flow with AI-based visualization and geological observation, mantle convection rolls can be treated as physically coherent structures linking Earth’s deep interior to its surface expression. Rather than being abstract or speculative, they offer a unifying framework for understanding why geological features appear where they do.
Here, a geometrically constrained, physics-motivated model for the large-scale convection architecture of Earth’s interior, is developed. The central objective is to show that the apparent complexity of surface geology can be understood as the surface expression of a comparatively regular interior system—one that is (i) consistent with the known physical behavior of convective flow and (ii) strictly constrained by geophysical measurements of Earth’s layered structure.
The method is intentionally bottom-up. It begins with measured layer thicknesses and a small number of physical principles, imposes a strict geometric requirement on how convection must occupy those layers, derives a three-dimensional convection-cell architecture, and only then (in Part II) compares the resulting predictions with surface observations such as fault systems, mid-ocean ridges, volcanic zones, and geothermal provinces. Iceland serves as a particularly powerful natural laboratory because multiple parts of the system intersect there.
The 12 main division lines of the lower mantle convection rolls system.
A chain of implications:
Layering → Geometry Earth’s measured internal stratification defines fixed radial spaces that convection must occupy.
Physics → Cell proportions Rayleigh–Bénard convection under balanced conditions favors rolls with comparable vertical and horizontal dimensions.
Exact filling → Discrete structure When layers are required to be filled exactly by RB roll sections, characteristic cell sizes and integer counts emerge.
Rotation → Curvature Earth’s rotation constrains the horizontal planform of flow, producing systematic curvature and latitudinal organization.
Continuity → Intersection zones Global circulation requires geometrically defined zones where different roll families and layers connect smoothly.
Petrology → Two-layer interpretation The resulting upper-mantle structure naturally accommodates two chemically distinct source regions, consistent with MORB and OIB.
Heat transport → Focused pathways Convection, conduction, radiation, and focused melt transport together explain how a regular interior system can produce localized surface volcanism.
The guiding premise throughout Part I is that regularity is the default expectation for a slowly evolving, rotating convective system operating over geological timescales inside a nearly spherical body.
Background
When Earth’s internal layers—defined seismologically—are drawn to scale, their thicknesses exhibit a degree of regularity that invites geometric testing. The working hypothesis is that this regularity is not accidental: convection within the Earth organizes itself in a way that fills the available radial space efficiently and repeatedly.
The model does not introduce new physics. Instead, it organizes existing measurements within a coherent geometric and physical framework, extending classical ideas about mantle convection and plate motion in the conceptual tradition of Sir Arthur Holmes and Harry Hess, besides Alfred Wegener and others. The novelty lies in enforcing internal consistency across all layers simultaneously.
The governing preconditions are deliberately minimal:
Thermal forcing: sustained heat flow requiring convection in the mantle and outer core.
Rotation: Earth’s spin, introducing Coriolis constraints on horizontal flow.
Measured stratification: seismically determined depths of major boundaries and transition zones.
If convection has operated for billions of years in a thick, relatively homogeneous mantle, logic suggests that the system approaches a balanced, quasi-steady organization. Under such conditions, repetitive structures are expected rather than arbitrary ones.
Radial geometry and the primary constraint
The central requirement of the model is simple and strict:
Each convecting layer must be exactly filled by sections of Rayleigh–Bénard convection rolls, without adjustment of dimensions. The roll geometry is determined solely by this requirement and by the physical tendency of RB convection toward comparable vertical and horizontal length scales.
No internal length scale is assumed in advance. Instead, the measured thicknesses of the layers define the available space, and the roll dimensions must adapt to that space under the constraint of exact geometric filling. The geometry then follows the rotational plane of the Earth, starting with the equatorial plane where convection flow and centrifugal force coincide in one plane.
To make the geometry explicit, the conventional “surface-down” description of Earth’s structure is reformulated as a center-out radial system. This allows roll sections to be constructed directly within each layer. When this is done, a regular packing of roll sections emerges that simultaneously satisfies multiple layer boundaries, including the core–mantle boundary region and the upper mantle transition near ~410 km.
The key point is logical rather than numerical: when a single roll geometry fits several independent, measured layers without tuning, the probability of coincidence becomes small. The consistency itself becomes the result.
Upper mantle structure and the 410 km and 670 km discontinuities
Attention then shifts to the part of the Earth most directly coupled to surface geology: the upper mantle and asthenosphere.
Two boundaries define the active convective domain beneath tectonic plates:
an upper boundary near ~120 km, where behavior shifts from conduction-dominated lithosphere to convection-dominated asthenosphere;
a lower boundary near ~410 km, marking the top of the large lower-mantle convection system in this framework.
This creates approximately 290 km of vertical space. When exact RB roll filling is imposed on this interval, simple trigonometry shows that only certain discrete arrangements are possible. A particularly robust solution yields 240 convection cells around the globe in the upper layers, corresponding to a longitudinal spacing of 1.5°.
This number is not arbitrary. It is constrained by symmetry, by divisibility relative to the deeper system, and by the requirement that upper and lower systems nest coherently. The result is a hierarchical structure: large rolls below and smaller rolls above.
The interval between ~410 km and ~670 km is found to accommodate additional roll systems, also with a longitudinal spacing of 1.5°, nested within the larger cells. These secondary systems do not replace the primary structure but supplement it, allowing vertical and horizontal circulation to remain continuous.
Horizontal geometry, rotation, and curvature
With the vertical structure established, the model turns to horizontal geometry. In a rotating system, convection cannot remain rectilinear. The Coriolis effect causes flow paths to curve in systematic ways.
Using inertial-flow reasoning, the characteristic horizontal scale of unconstrained motion on a rotating Earth is of the order of Earth’s radius. To represent this geometry, a square latitude–longitude grid is used as a drawing space, with the understanding that it is a mathematical convenience rather than a physical projection.
Imposing two constraints—
fixed separation of roll boundaries at the equator, and
latitude-dependent horizontal scaling proportional to 1 / cos φ—
leads to a compact geometric condition whose solution identifies a characteristic latitude near 32° N and S. Circles centered near these latitudes reproduce the required horizontal dimensions while remaining consistent with rotational physics.
Earth is not a perfect sphere, but a geoid. Because curvature deviations are not uniformly distributed with latitude, the operational center is taken as approximately 32.0°, which is makes geological-scale predictions possible.
The resulting map-level representation consists of families of circular roll boundaries spaced at 1.5° intervals, supplemented by polar roll families that connect smoothly to the hemispheric system.
Importantly, the circle equations themselves are dimensionless. Angular degrees enter only when the geometry is interpreted on Earth’s surface.
MORB and OIB as expressions of a two-layer system
The geometric framework naturally accommodates a petrological distinction long recognized at the surface: MORB versus OIB.
In the model, these correspond to two vertically stacked convection layers within the upper mantle. The upper layer supplies MORB to mid-ocean ridges, while the lower layer samples deeper or compositionally distinct material consistent with OIB.
Horizontal circulation is described as linked semicircular segments: material travels along a semicircle in one layer and returns along a complementary semicircle in the other, forming a closed loop. This architecture allows continuous circulation while limiting mixing—precisely what is required if MORB and OIB remain distinct over geological time.
When the derived circle families are plotted on a world map, individual boundaries often align with major geological structures. These alignments are not assumed in advance; they become testable predictions.
Heat transfer, radiation, and focused pathways
While convection is the dominant mode of heat transport, conduction and radiation also play roles. At high temperatures, mantle materials may become increasingly transparent to thermal radiation, effectively enhancing internal heat redistribution.
In this framework, radiative transfer allows heat generated in upper layers—where radioactive elements are concentrated—to contribute to deeper thermal budgets, with convection redistributing that energy upward again.
At the boundaries between convection cells, focused upward melt transport is proposed to occur via Munroe-type effects, where geometric and thermal focusing produce narrow, persistent conduits. These conduits provide a mechanism by which a broadly regular convection system can generate sharply localized volcanism and geothermal anomalies.
Intersection zones and global continuity
A global circulation system must close smoothly. This requires intersection zones where different roll families and layers connect without violating rotational constraints.
Two principal types are identified:
Mid-to-high latitude intersections (~60.7°–67.3°), where hemispheric and polar roll systems meet. Near ~64°, roll directions become tangent, allowing exchange without disrupting curvature.
The equator, where the Coriolis effect changes sign. Here, flow must reverse curvature or transfer between layers, imposing strong geometric constraints that may explain large-scale equatorial regularities.
In these zones, effective layer doubling or reorganization may occur, producing greater structural complexity. Iceland lies within such an intersection region, explaining its unusually rich geological expression.
Integrated logic
The model proceeds as a single logical construction:
measured stratification defines the available space,
RB convection physics constrains roll proportions,
and extended heat-transfer mechanisms explain focused surface activity.
The outcome is a coherent, testable three-dimensional framework. It produces explicit geometric predictions—locations, orientations, and characteristic spacings—that can be confronted directly with geological and geophysical observations.
Magic Magma 