Ring Of Fire

Interpretations of volcanic phenomena have long been framed by the imagery of fire; from classical antiquity through the 18th century eruptions and thermal activity were commonly explained as burning within the Earth, an association that survives in the modern name “Ring of Fire” despite the fact that magmatism does not result from literal internal combustion. Systematic recognition of a circumpacific band of volcanism emerged in the early 19th century, when geologists such as G. P. Scrope documented the concentration of volcanic chains along the Pacific margins and emphasized their spatial continuity. Mid‑19th century exploratory reports reinforced this view by explicitly linking volcanic zones from South America to East and Southeast Asia, and late‑19th‑century scientific journalism in the United States popularized the concept for a broader audience. By the early 20th century the phrase had become commonplace in public accounts of seismic disasters, while technical refinements—most notably Patrick Marshall’s 1912 formulation of the Andesite Line, which separated regions of differing volcanic style and magma chemistry in the southwest Pacific—provided more detailed regional distinctions that largely correspond to the broader circum‑Pacific pattern. The advent and widespread acceptance of plate‑tectonic theory in the 1960s supplied the mechanistic framework explaining why earthquakes and volcanism concentrate around the Pacific basin, thereby unifying earlier descriptive and observational work into the modern understanding of the Ring of Fire.

Geographic boundaries

The Ring of Fire is principally delineated by volcanism and seismicity generated at subduction zones; its principal segments are broadly agreed upon, but several marginal regions are contested among specialists. A notable point of overlap occurs in Indonesia, which lies at the junction of the Ring of Fire and the east–west trending Alpide (Mediterranean–Indonesian) belt, leading to differing treatments of Indonesia’s western islands as belonging either to the Ring of Fire or to the Alpide system. Similarly, some researchers include the Antarctic Peninsula and the South Shetland Islands within the Ring of Fire, while the remainder of Antarctica is generally excluded because volcanism there is not driven by subduction. The Ring does not form an unbroken circumpacific band across the southern Pacific: the dominant submarine boundaries between New Zealand, the Antarctic Peninsula and southern South America (the Pacific–Antarctic Ridge, East Pacific Rise and Chile Ridge) are divergent spreading ridges whose volcanism is not subduction-related and thus falls outside the Ring of Fire concept. Inclusion of certain island arcs (for example the Izu, Bonin and Mariana chains) likewise varies across the literature, reflecting complex local plate interactions and different operational criteria for boundary assignment.

These divergences in mapping arise from three interrelated causes: whether a plate boundary is convergent or divergent, the existence of overlapping volcanic belts (Ring of Fire versus Alpide), and ambiguous configurations at plate junctions and island arcs. Consequently, the geographic limits of the Ring of Fire are partly interpretive and contingent on the tectonic criteria researchers adopt rather than strictly uniform lines on a map.

Land areas (Ring of Fire)

The Pacific “Ring of Fire” consists of a near-continuous band of convergent plate margins around the Pacific Basin where oceanic lithosphere descends beneath continental or other oceanic plates. This global subduction system produces linear continental volcanic belts and chains of island arcs, characterized by stratovolcanoes, volcanic fields, explosive arc volcanism, and associated back‑arc basins and accreted terranes. The principal land-area expressions of this subduction-related belt fall into contiguous regional segments that reflect differences in plate geometry, lithosphere type (continental versus oceanic), and microplate complexity.

Along South America the Ring of Fire is manifested by the Andes, an active continental arc subdivided into four principal volcanic belts (North, Central, South, Austral) that together form a near-continuous chain of stratovolcanoes and volcanic fields on the continent’s western margin as oceanic plates subduct beneath the South American plate. At high southern latitudes the Antarctic sector includes volcanic provinces adjacent to the Antarctic continent and Southern Ocean—most notably the Antarctic Peninsula and oceangoing arc systems such as the South Sandwich Islands—which record subduction and magmatism in the southernmost Pacific.

North and Central America host a linked suite of subduction-related volcanic regions along the Pacific margin: the Cascade Volcanic Arc in the northwestern United States and southwestern Canada; the Trans‑Mexican Volcanic Belt across central Mexico; and the Central America Volcanic Arc extending down the isthmus. Farther north and west, the Aleutian Arc—extending from mainland Alaska through the Aleutian Range and island chain—represents an extensive intra‑Pacific island arc formed by subduction beneath the North American plate.

Northeastern Eurasia contains major arc systems such as Kamchatka and the Kuril Islands, where descending oceanic plates generate concentrated, often explosive arc volcanism. The western Pacific and East Asian arcs include Japan, the Ryukyu Islands, Taiwan and the Philippine Mobile Belt; these regions are marked by complex plate interactions, multiple microplates and accreted terranes, intensive island‑arc magmatism, and development of back‑arc basins. The Izu–Bonin–Mariana chain is a classic intra‑oceanic arc sequence—Izu, Bonin, Mariana—illustrating progressive stages of island‑arc formation.

Eastern Indonesia and adjacent island groups (including Tanimbar and Kai) occupy highly complex convergent margins where interactions among the Australian, Pacific and numerous microplates generate localized volcanic arcs and tectonically active island chains. The southwestern Pacific comprises many island‑arc and back‑arc volcanic provinces—Bismarck Archipelago, Vanuatu, Bougainville, the Solomon Islands, Fiji, Tonga, the Kermadecs—and includes the Taupō Volcanic Zone on New Zealand’s North Island, a distinctive intra‑continental arc with exceptionally explosive silicic volcanism.

Volcanic chains that originate from intraplate processes, however, lie outside the Ring of Fire. Central Pacific islands such as Hawai‘i are products of mantle plumes or hotspots and are not components of the subduction‑defined Ring of Fire.

Tectonic plate configurations

The Pacific Ring of Fire is a circum‑Pacific belt of concentrated volcanism and seismicity whose present expression reflects a long history of subduction and plate reorganization. While some subduction processes around the basin predate the modern system by tens of millions of years, the Ring of Fire as a coherent, geologically active feature has been developing for more than 35 million years, with earlier phases extending back substantially farther.

The current tectonic morphology resulted from a sequential establishment and migration of convergent margins around the Pacific. By about 115 million years ago, many of the principal subduction zones were already active along the western and eastern margins of the ocean—along present‑day South America, North America, and Asia—giving rise to enduring volcanic arcs and trench systems. A later pulse of boundary reorganization around 70 million years ago generated the complex array of oblique and intra‑oceanic subduction zones that underlie the Indonesian archipelago and New Guinea, adding major structural complexity to the western Pacific margin. The development of the New Zealand subduction system roughly 35 million years ago represents the most recent large‑scale step in assembling the circum‑Pacific subduction network, effectively completing the primary sequence of convergent‑margin formation that defines the modern Ring of Fire.

Past plate configurations

During the Mesozoic the circum‑Pacific realm evolved through a sequence of plate births, migrations and prolonged subduction that progressively established the convergent margin architecture seen today. By the Late Triassic (~210 Ma) the Izanagi (Paleo‑Pacific) plate was already subducting beneath eastern Asia, initiating arc volcanism that persisted into the Jurassic and produced volcanic belts now preserved in parts of eastern China. Early Jurassic reconstructions (ca. 180 Ma) place nascent oceanic plates within a reorganizing basin: the Pacific plate itself originated somewhat earlier in the Early Jurassic (≈190 Ma) away from basin margins, so older oceanic lithosphere at the margins continued to be consumed until the newly formed Pacific expanded to contact them. Concurrently, subduction along the western margin of South America was established in the Jurassic and has remained active since, leaving Jurassic–Cretaceous arc remnants preserved in the continental margin.

Through the Cretaceous the plate system underwent major reconfigurations. In the mid‑Cretaceous (≈120–115 Ma) the Farallon plate was subducting beneath South and North America and parts of north‑east Asia while Izanagi continued beneath east Asia, producing widespread convergent‑margin tectonism. Between ~85 and 70 Ma Izanagi migrated northeastward and began to underplate both east Asia and North America, the Farallon persisted beneath South America, and the Pacific plate began to impinge on east Asia. At the Cretaceous–Paleogene transition (≈70–65 Ma) the regional pattern comprised Farallon subduction beneath South America, Kula subduction beneath North America and north‑east Asia, and Pacific subduction beneath east Asia and proto‑Papua New Guinea. By the Neogene (≈35 Ma) the Kula and Farallon plates had been fully consumed; the Pacific plate then subducted broadly around its margins, producing a plate‑boundary configuration closely resembling the modern circum‑Pacific Ring of Fire.

Present-day plate configuration

The tectonic architecture of the Ring of Fire exhibits a clear east–west contrast: its eastern sectors are controlled by interactions among a few large plates, producing relatively continuous convergent margins, whereas the western and southwestern sectors comprise many large and small plates whose collisions generate a complex mosaic of subduction zones and island arcs.

Along South America the western margin is formed by the steady subduction of three oceanic plates—the Antarctic, Nazca and Cocos plates—beneath the continental South American Plate, creating a continuous convergent margin along the continent’s Pacific coast. In Central America the principal interface is the Cocos Plate descending beneath the Caribbean Plate, which produces the active volcanic and seismic belt that parallels the isthmus. The western North American margin exhibits mixed behavior: segments of the Pacific Plate and the smaller Juan de Fuca Plate are being subducted under the North American Plate, resulting in discrete subduction segments rather than a single uninterrupted trench.

In the northern Pacific the northwestward-moving Pacific Plate is consumed beneath the Aleutian arc, forming the Ring’s northernmost arc–trench system, and farther west the same Pacific Plate subducts beneath the Kamchatka Peninsula and the Kuril arcs, driving intense volcanism and seismicity along those convergent margins. In East and Southeast Asia, subduction of the Philippine Plate beneath the Eurasian Plate underpins major convergent activity in the regions of Japan, Taiwan and the Philippine archipelago, where oceanic descent occurs adjacent to continental margins. The southwestern quadrant is the most structurally intricate: numerous small plates interact with the Pacific at discrete island-arc and trench systems (for example the Marianas, the Philippine archipelago, eastern Indonesia, Papua New Guinea, Tonga and New Zealand). By contrast, the Australian landmass does not form an active margin within the Ring because it lies near the centre of the Australian Plate and is therefore removed from primary subduction zones.

Collectively, these configurations produce spatially variable arc–trench architectures and associated patterns of volcanism and seismicity, ranging from long, continuous convergent margins to highly segmented, microplate-dominated systems.

Subduction zones and oceanic trenches

Pacific‑margin volcanism is governed by two end‑member subduction modes that reflect the nature of the overriding plate. When oceanic lithosphere descends beneath another oceanic plate it produces an island‑arc system exemplified by the Mariana Arc; when oceanic lithosphere subducts beneath continental crust it generates a continental volcanic arc such as along the Chilean margin. Mechanically, the difference stems from whether volcanism and deformation are built upon oceanic or continental crust, but both arise from the same process of slab descent and associated mantle wedge melting.

The angle at which a slab sinks is a first‑order control on margin style and is principally set by the thermal state and density of the subducting plate: older, colder, denser oceanic lithosphere tends to sink steeply, whereas younger, warmer and more buoyant lithosphere subducts at shallower angles. In the Pacific this control is amplified by asymmetric mid‑ocean ridge geometry: ridges lie closer to South America than to Asia, so the lithosphere entering South American subduction zones is relatively young and produces generally shallow slabs, whereas the western Pacific consumes older lithosphere and characteristically steeper slabs.

Variation in slab dip produces systematic geological and geomorphological contrasts. Steeply dipping slabs place arc volcanoes nearer the trench, favor deeper mantle‑wedge melting signatures and generate deeper‑focal earthquakes; shallowly dipping slabs drive magma production farther inland, favor growth of large accretionary prisms through sediment accretion or remove material by subduction erosion, and promote shallow crustal seismicity and broad compressive deformation. These differences also influence lava chemistry through differing melt depths and slab–mantle interactions and alter the margin stress regime (relative amounts of horizontal compression or extension).

Rather than a binary classification, subduction geometries form a continuum with Chilean‑type (shallow, continental‑arc) and Mariana‑type (steep, island‑arc) as end members. Intermediate configurations reflect combinations of slab age, ridge position, plate motions and local tectonic history. The Ring of Fire, encircling the Pacific, provides the regional framework in which both oceanic–oceanic and oceanic–continental systems coexist, demonstrating how ridge placement and lithospheric age together dictate arc morphology, magmatism, seismic behaviour and attendant geohazards.

Oceanic trenches

Oceanic trenches are the principal bathymetric expression of subduction: narrow, elongate depressions formed where one lithospheric plate flexes and descends beneath another. At convergent margins they coincide with intense seismicity—earthquake epicenters that commonly align with the trench axis and define a dipping Wadati–Benioff plane that extends into the mantle—and with volcanic arcs and other manifestations of elevated geodynamic activity. Together these trenches form the circum‑Pacific system commonly termed the “Ring of Fire,” a continuous belt of subduction margins, island and continental arcs, and concentrated volcanism and earthquakes encircling the Pacific Basin.

Detailed seismicity maps (for example of the Kuril–Kamchatka system) illustrate the characteristic spatial pattern: a dense, linear concentration of shallow epicenters along the trench and a deeper inclined plane of earthquakes landward that records the geometry of the downgoing slab and its relation to the overlying volcanic arc. Individual trenches within this system vary in plate partners, curvature, convergence rate and tectonic consequences:

Peru–Chile Trench: the long convergent margin off western South America where the Nazca Plate subducts beneath the South American Plate, controlling the tectonics and seismic hazard of the Peruvian and Chilean coasts.
Middle America Trench: the offshore trench along Mexico and Central America where the Cocos and Rivera lithospheres descend beneath the North American and Caribbean plate systems, producing strong seismicity along the Pacific coasts of southern Mexico and Central America.
Aleutian Trench: the arcuate trench south of the Alaska Peninsula and along the Aleutian arc where the Pacific Plate subducts beneath North America, linking an extended zone of earthquakes and arc volcanism.
Kuril–Kamchatka Trench: off the Kuril Islands and Kamchatka, this margin records dense seismicity and a prominent volcanic arc as the Pacific Plate descends beneath the Okhotsk/North American plate system.
Japan Trench: east of Honshu, where Pacific Plate subduction beneath the Okhotsk/Northeast Asia margin is a principal source of Japan’s deep and destructive earthquakes and supports the northeastern Japanese volcanic arc.
Ryukyu Trench: the arcuate trench south of Kyushu and Okinawa produced by Philippine Sea Plate subduction beneath the Eurasian margin and associated with the Ryukyu island arc.
Izu–Bonin Trench: a south‑of‑Japan trench where Pacific Plate subduction beneath the Philippine Sea Plate generates an intra‑oceanic volcanic arc extending through the Izu and Bonin islands.
Mariana Trench: the western Pacific trench system that contains the Challenger Deep, the ocean’s greatest depth, marking Pacific Plate descent beneath the Mariana arc and exemplifying extreme trench depth and subduction processes.
Yap Trench: a component of the complex western Pacific subduction framework near the Caroline Islands that contributes to local seismicity and regional plate interactions.
Philippine Trench: east of the Philippines, where subduction of the Philippine Sea Plate and adjacent oceanic lithosphere beneath the Philippine mobile belt produces major earthquakes and complicates arc‑forearc tectonics.
Sunda (Java) Trench: the long eastern Indian Ocean trench off Sumatra and Java where the Indo‑Australian Plate subducts beneath the Sunda (Eurasian) Plate, forming one of the planet’s most active convergent margins and governing Indonesian western‑island tectonics.
Tonga and Kermadec Trenches: forming a linked southwest Pacific system north of New Zealand and adjacent to Tonga, these trenches record some of the fastest convergence rates and most intense trench–arc seismicity worldwide, with the Kermadec forming the northern continuation toward New Zealand.
Hikurangi Trough: the subduction margin east of New Zealand’s North Island (the Hikurangi margin), where Pacific Plate descent beneath the Australian/Zealandia margin produces classic trench–forearc–arc relationships and a spectrum of seismic behavior including episodic slow‑slip events.

Collectively, these trenches define the geometry and dynamics of convergent plate boundaries around the Pacific and adjacent basins; their variations in depth, curvature, convergence rate, and plate coupling control the distribution and style of earthquakes, volcanism and long‑term orogenic and basin development along the Ring of Fire.

The volcanic belt commonly referred to as the Ring of Fire does not form an unbroken arc around the Pacific; breaks in subduction along the margin produce spatial gaps where arc volcanism is absent or replaced by volcanism driven by other tectonic regimes. These discontinuities arise when plate-boundary type or geometry changes: active, steep-angle subduction sustains the mantle-wedge melting that generates volcanic arcs, whereas shallow (flat‑slab) subduction, cessation of subduction, transitions to divergent motion, transform faulting, or intraplate extension all suppress or alter arc-style magmatism.

A prominent mechanism is flat‑slab subduction, which reduces or removes the mantle wedge and thereby inhibits the melt generation that feeds an arc. This process subdivides the Andean Volcanic Belt into four segments separated by three volcanically quiet gaps attributed to episodes of shallow-angle subduction. Along the Pacific margin of North America, a large gap in subduction-related volcanism across northern Mexico and southern California reflects the combined influence of the Gulf of California—a zone of active continental rupture and divergence—and the San Andreas Fault, a predominantly strike‑slip transform system that does not produce a subduction arc. Further north, in northern British Columbia, Yukon and southeast Alaska, the dominant magmatism is linked to intraplate continental rifting and extensional tectonics rather than to an ocean‑plate subduction regime.

Thus, the observed pattern of Pacific volcanism is controlled not simply by whether subduction is present but by its geometry and by where margins switch to divergent, transform, or intraplate extensional regimes. The result is a Ring of Fire that is spatially discontinuous and tectonically heterogeneous, with volcanic gaps marking locations where subduction-related processes are absent or strongly modified.

Distribution of Holocene Ring of Fire Volcanoes

The dataset documents Holocene (last 11,700 years) volcanic centers conventionally associated with the Ring of Fire. In total it records 913 volcanoes attributed to subduction-zone settings and 59 volcanoes classified as “other” (intraplate, continental- or oceanic-rift, mantle-plume-related volcanoes and seamounts). Each regional entry records submarine occurrences, cross‑border volcanoes, specific exclusions (notably hotspot islands) and whether the region is generally regarded as part of the Ring of Fire.

Regional patterns
– General pattern: the Ring of Fire is overwhelmingly composed of subduction-related volcanoes; non‑subduction types occur locally (rift systems, intraplate or plume-influenced centers), often associated with back‑arc rifting or localized mantle upwellings. Submarine volcanoes and seamounts are frequent in island arcs and back-arc basins, and several island groups or hotspot chains are explicitly excluded from Ring-of-Fire counts.

Antarctica
– Antarctic Peninsula (Graham Land) and the South Shetland Islands contain only a few intraplate/rift centers (Peninsula: 3; South Shetlands: 4). The South Shetland volcanism is linked to back‑arc rifting but neither area is generally counted as part of the Ring.

South America
– The Pacific margin of South America is dominated by subduction volcanoes concentrated in Chile (71), with additional border-region clusters (Chile–Argentina 18; Chile–Bolivia 6; Chile–Peru 1). Peru (16), Ecuador (21, excluding the Galápagos hotspot), Colombia (13) and Argentina (15 subduction + 4 intraplate) complete the continental distribution. Bolivia (5) and Argentina’s inland intraplate volcanism are noted but national portions without Pacific frontage are typically not considered part of the Ring. Easter Island and the Galápagos are treated as oceanic hotspot features and excluded from Ring counts.

North America (including Central America, Mexico, United States, Canada)
– Central America shows dense subduction volcanism: Panama 2, Costa Rica 10, Nicaragua 17, Honduras 4, El Salvador 18, Guatemala 21 (including border entries with neighboring states). Mexico totals 26 subduction volcanoes plus 8 continental rift volcanoes (principally in Baja California); three oceanic rift volcanoes are excluded. The contiguous United States (California, Oregon, Washington) lists 22 subduction and 9 continental-rift volcanoes. Canada records 6 subduction and 16 intraplate volcanoes (excluding two oceanic rift centers). Alaska is a major node with 80 subduction-zone volcanoes (including 39 in the Aleutians) and 4 intraplate centers in southeast Alaska; some remote intraplate centers in western Alaska are excluded from the subduction tally. All these areas are generally accepted as Ring of Fire territory.

Asia (northeast and southeast arcs)
– The western Pacific island arcs and adjacent continental margins show high subduction counts: Kamchatka (Russia) 67; Kuril Islands 44 (including three submarine centers; multiple peaks claimed by Japan); Japan’s main islands 81 (Izu and Bonin excluded from that figure); the Izu–Bonin region itself lists 26 subduction centers (many submarine) but is not universally treated as part of the Ring in this compilation. Taiwan contributes 4 subduction centers (two submarine). The Philippines registers 41 subduction volcanoes. Indonesia’s Sunda Arc (Sumatra, Java, Bali, etc.) accounts for about 70 subduction centers (Sumatra 27; Java 36; plus Krakatoa and smaller islands) though the Sunda region’s inclusion is treated variably; Indonesia’s eastern islands add ~54 subduction volcanoes and are considered part of the Ring. Papua New Guinea records 47 subduction volcanoes and one rift volcano. The Northern Mariana Islands and Guam include many submarine arc volcanoes but their inclusion is not unanimous.

Oceania and the South Pacific
– Island arcs and back‑arc zones in the southwest Pacific contain numerous subduction centers: Solomon Islands 8 (four submarine), Vanuatu 14, Tonga 17 (13 submarine, three identified as back‑arc rift type), New Zealand mainland 20 (including submarine centers) and the Kermadec Islands 6 (mostly submarine). Monowai seamount (between Tonga and the Kermadec arc) is listed as a subduction-related feature. Smaller island groups and certain territories (e.g., Wallis and Futuna, Samoa, American Samoa, Izu/Bonin, parts of New Caledonia claims and some French/Vanuatu-claimed features) show mixed genesis (plume influence, rifting or hybrid processes) and are variably included in Ring counts; specific seamounts (e.g., Hunter, Matthew, East Gemini) are singled out in the record.

Summary implications
– The spatial distribution confirms the Ring of Fire as a primarily subduction-driven circum‑Pacific belt with concentrated clusters along continental margins and island arcs. Non‑subduction volcanoes are comparatively rare in the Holocene Ring record but are significant in particular localities (back‑arc rifts, continental rift zones, plume-influenced islands), and classification/region‑inclusion decisions in several island groups introduce region‑by‑region variability in whether features are treated as part of the Ring.

Volcanic activity in the Holocene (the last 11,700 years) is strongly concentrated along the circum‑Pacific “Ring of Fire,” the tectonically active margin encircling the Pacific basin. The four single most voluminous explosive eruptions of the Holocene all occurred at Ring of Fire volcanoes: Fisher Caldera in Alaska (eruption dated ca. 8700 BCE) in the North American sector; the Kurile Lake event on the Kamchatka Peninsula (ca. 6450 BCE) in the Russian Far East arc; the climactic eruption of Mount Mazama in present‑day Oregon (ca. 5677 BCE) along the northeastern Pacific margin; and the Kikai Caldera eruption in southern Japan (ca. 5480 BCE) within the western Pacific arc.

These four cases exemplify the Ring of Fire’s propensity to generate very large explosive eruptions, a pattern that extends beyond them: of the 25 largest Holocene eruptions, 20 are associated with Ring of Fire volcanoes. This spatial clustering reflects the region’s dominant subduction‑zone tectonics and magmatic processes, which have produced the majority of the epoch’s most voluminous explosive events.

Earthquakes

The Pacific Ring of Fire constitutes the principal global locus of seismic activity, concentrating roughly 90% of earthquakes and the majority of the largest recorded shocks. This circum‑Pacific belt coincides with numerous convergent plate margins and active subduction zones, where plate‑interface processes concentrate strain and enable the largest seismic energy releases.

The Alpide seismic belt is the second most active global zone, accounting for about 5–6% of earthquakes; it stretches from central Indonesia westward through the Himalayas and southern Europe to the northern Atlantic, linking tectonic deformation across South and Eurasia.

A temporal assessment for 1900–2020 indicates that most events of magnitude Mw ≥ 8.0 occurred within the Ring of Fire and are interpreted predominantly as megathrust earthquakes at subduction interfaces. Classic examples of the extreme seismic potential of these plate boundaries include four 20th–21st century Ring‑of‑Fire megathrusts measured since the 1930s: the 1960 Valdivia, Chile (Mw 9.4–9.6); the 1964 Alaska, USA (Mw 9.2); the 2011 Tōhoku, Japan (Mw 9.0–9.1); and the 1952 Severo‑Kurilsk, Kamchatka, Russia (Mw 9.0). These events exemplify how subduction‑zone mechanics produce the largest observed earthquakes.

Antarctica

Antarctic volcanic activity is classified relative to the Pacific Ring of Fire according to the tectonic processes that generate it; only volcanoes genetically linked to subduction-related convergent margins are commonly regarded as part of the Ring. Consequently, inclusion is not uniform across the continent but depends on local plate interactions.

Volcanism in the South Shetland Islands, notably at Deception Island, reflects explosive interactions between magma and external water (phreatomagmatic deposits) and is attributed to rifting in the Bransfield back-arc basin adjacent to the South Shetland subduction zone. Because this rift-related volcanism occurs in the immediate tectonic setting of a subduction system, many researchers treat these centers as extensions of Ring of Fire processes.

The northern Antarctic Peninsula (Graham Land) is similarly sometimes incorporated into Ring of Fire discussions on the basis of its tectonic linkages to nearby subduction and back-arc activity; this reflects a conditional, tectonics-based inclusion rather than a blanket designation for Antarctic volcanism.

By contrast, volcanic provinces south of the Antarctic Circle—including Victoria Land (home to Mount Erebus), the volcanic fields of Marie Byrd Land, and the Balleny Islands—are not products of subduction. Their magmatism arises from intraplate or other non-convergent processes and therefore are generally excluded from Ring of Fire inventories.

In summary, the key criterion for assigning Antarctic volcanoes to the Ring of Fire is a demonstrable genetic connection to subduction-related tectonics; where such a link is absent, volcanic centers are not classified as part of the Ring.

South America — Ojos del Salado and Llullaillaco

Ojos del Salado (6,893 m / 22,615 ft) and Llullaillaco (6,739 m / 22,110 ft) are among the highest volcanic summits on Earth, located in the central Andes where the Pacific Ring of Fire intersects the Argentina–Chile cordillera. Ojos del Salado, situated on the international boundary, is recognized as the world’s highest active volcano, with its most recent known eruptive activity dated to AD 750. Llullaillaco, also straddling the Argentina–Chile border, is identified as the highest historically active volcano, with the last recorded eruption in 1877. Their elevations underscore that significant arc volcanism in the Andes can produce very high-altitude volcanic edifices.

These volcanoes form in the convergent margin produced by subduction of the Nazca Plate beneath the South American Plate, a tectonic regime that generates a volcanic arc and the tall stratovolcanoes characteristic of the region. Because both peaks lie on or contribute to the international boundary, their high‑altitude volcanism carries binational implications for land use, jurisdictional management, and scientific monitoring. The late Holocene (AD 750) and historical (1877) eruption dates support their designation as active or historically active, indicating a non‑negligible potential for future activity and the need for continued volcanological observation, particularly given the logistical challenges of alpine environments.

Chile’s segment of the Andean volcanic arc exhibits intense magmatic activity: roughly 90 volcanoes have been active during the Holocene, displaying a broad spectrum of eruptive styles and generating diverse hazards (lava flows, pyroclastic flows, ashfall, lahars and ballistic ejecta) along the length of the country. This activity is a direct consequence of subduction of the Nazca Plate beneath South America and is closely coupled to the nation’s seismicity.

Prominent volcanic centers illustrate the variety of behaviors. Villarrica, perched above a lake and the eponymous town, is the westernmost of a trio of large stratovolcanoes aligned across the arc; its dominantly basaltic–andesitic magmas sustain one of the few persistent lava lakes known globally. Villarrica’s typical mode is Strombolian activity with incandescent pyroclasts and lava effusion, but its edifice also preserves a 2 km-wide postglacial caldera, numerous flank scoria cones, and evidence for larger Plinian and pyroclastic-flow events in the Holocene. Repeated melting of summit snow and ice during eruptions—exacerbated by heavy rainfall—has produced destructive lahars that have damaged settlements (notably in 1964 and 1971).

Llaima, located in Conguillío National Park, is among Chile’s largest and most persistently active volcanoes, with historical records extending to the 1600s. Its eruptive history is characterized by episodic moderate explosive eruptions with occasional lava flows, including notable episodes in recent decades (e.g., 2008). In the northern Andes, Lascar has been the region’s most active volcano: after very large late-Quaternary eruptions and a Holocene reorganization of vents that produced overlapping craters, it has produced frequent small-to-moderate explosive events since the mid‑19th century and sporadic larger eruptions whose ash and tephra have traveled hundreds to over a thousand kilometres (the 1993 event produced pyroclastic flows and distal ashfall reaching Buenos Aires).

Smaller volcanic systems also show variable behavior. Chiliques, in the Antofagasta Region near Cerro Miscanti and Laguna Lejía, has exhibited renewed thermal activity after many millennia of quiescence; satellite thermal infrared imagery detected a summit/upper-flank hotspot in January 2002 that was absent two years earlier, indicating recent heating of the shallow system. Calbuco, a highly explosive andesitic stratovolcano in the Los Lagos Region, experienced a late-Pleistocene edifice collapse and has produced at least nine historical eruptions since 1837. Its documented activity includes violent 1893–1894 eruptions with widespread ballistic ejecta and hot lahars, dome growth and lahars in 1917, a mixed pyroclastic–lava event in 1929, and a major 1961 eruption that injected ash to 12–15 km altitude. Lonquimay, a primarily andesitic, truncated-cone volcano in La Araucanía within the Malalcahuello–Nalcas protected area, produced a VEI 3 flank eruption between 1988 and 1990 that generated lava flows and caused fatalities.

Hazard assessment and real-time monitoring in Chile are the responsibility of the National Geology and Mining Service (SERNAGEOMIN). The subduction-driven tectonic regime not only sustains prolific volcanism but also produces exceptional earthquakes—including the 1960 Valdivia event (the largest instrumentally recorded earthquake), the M8.8 central Chile earthquake of 27 February 2010 (which preceded the 2011 Puyehue–Cordón Caulle eruption), and the M8.2 northern Chile earthquake of 1 April 2014 with large aftershocks—underscoring the tightly coupled nature of seismic and volcanic hazards along the Chilean margin.

Bolivia

Bolivia contains both active and extinct volcanic centers, with active vents concentrated in the western part of the country and strongly shaping its volcanic landscape. These centers comprise the Cordillera Occidental, an active volcanic arc that marks the western structural and topographic limit of the Altiplano and represents the principal belt of recent volcanism in the region. The linear distribution of volcanoes along this margin both defines the Altiplano’s western edge and exerts a controlling influence on its geomorphology. Several of the active peaks lie on or very near the international boundary with Chile, so that some summits are shared between the two states. All Cenozoic volcanic edifices in Bolivia are components of the Central Volcanic Zone (CVZ), a major late Cenozoic segment of the Andean Volcanic Belt whose magmatism is produced by subduction of the Nazca Plate beneath the South American Plate; this plate‑tectonic interaction concentrates and organizes volcanism beneath the overriding continental margin.

Peru

Sabancaya and Ubinas are prominent active stratovolcanoes in the southern Peruvian Andes. Sabancaya rises to 5,976 m (19,606 ft) and lies roughly 100 km northwest of Arequipa; it has been the most persistently active volcano in Peru, with an eruptive phase that began in 2016 and has continued since. Ubinas attains 5,672 m (18,609 ft) and remains one of the region’s contemporary eruptive centers, most recently erupting in 2019.

Both edifices form part of the volcanic complex of southern Peru and are subject to continuous surveillance by the Peruvian Geophysical Institute, the national authority charged with volcano monitoring and associated geophysical observations.

Ecuador

Ecuador’s segment of the Ring of Fire is marked by a concentration of high, frequently active stratovolcanoes that pose significant tephra, lahar and pyroclastic hazards to both highland and lowland areas. Cotopaxi, located roughly 50 km south of Quito, attains 5,897 m and has erupted repeatedly (more than fifty events recorded since 1738), repeatedly generating voluminous lahars that have incised surrounding valleys and reshaped local topography. Pichincha, the volcanic complex immediately adjacent to Quito, has produced major tephra falls historically (notably in 1553, 1660 and October 1999), demonstrating the acute proximal ash hazard to the capital.

In central and eastern Ecuador, Sangay and Tungurahua form a dynamic volcanic ensemble within Sangay National Park. Sangay rises to about 5,286 m and is one of the country’s most persistently active volcanoes; its long (~500,000-year) history includes constructive growth and catastrophic flank collapses that have left widespread debris around the modern cone. Dominated largely by strombolian activity, Sangay has produced extended eruptive episodes (e.g., the 1934–2011 phase and subsequent events) and occupies a tectonically complex position astride two crustal blocks at the southern limit of the Northern Volcanic Zone. Tungurahua, located north of Sangay within the same protected area, has also been intermittently active and has produced incandescent lava emissions and explosive activity that contribute to the park’s volcanism. Sangay National Park, containing these active centers, is part of a UNESCO World Heritage Site.

Reventador, in the eastern Andes, exemplifies the region’s capacity for high-intensity eruptions; it has erupted more than 25 times since the 16th century, with a notably powerful 2002 event that produced a plume to ~17 km and pyroclastic flows extending ~7 km. Renewed activity beginning in 2008 was reported as ongoing into 2020, and intermediate events (for example, an ash column ~3 km high in 2007) punctuate its frequent unrest. National volcanic monitoring and hazard assessment are conducted continuously by the Instituto Geofísico of the Escuela Politécnica Nacional (EPN), which provides the principal observations, alerts and scientific information for Ecuador’s volcanic centers.

Central America’s segment of the Ring of Fire is exemplified by contemporaneous volcanic activity in Guatemala and Costa Rica during the early 2000s, notably the 2003 eruptive episode at Santiaguito and the pronounced crater morphology observed at Poás in 2004. Both volcanoes are integral parts of the Central American Volcanic Arc, where subduction of the Cocos Plate beneath the Caribbean Plate generates magmatism and surface volcanism. This shared tectonic driving mechanism accounts for the presence of active vents, summit craters, and dome complexes across the region.

Morphologically, the features recorded—Poás’s conspicuous summit crater and Santiaguito’s episodic dome/vent eruptions—reflect ongoing magmatic and hydrothermal processes. Such processes produce a range of volcanic landforms and episodic behaviour: explosive ash-producing eruptions, effusive dome growth with the potential for collapse, gas emissions, and interactions with surface water that can generate lahars. These processes impose multiple hazards to nearby populations and ecosystems, including ashfall, ballistic projectiles, pyroclastic density currents, toxic gases, and secondary sedimentary flows.

The temporal proximity of the 2003 and 2004 observations underscores the persistence of volcanic activity in the region and highlights the necessity for continuous volcanological monitoring. Sustained surveillance, hazard mapping and risk-reduction planning in countries such as Guatemala and Costa Rica are essential to detect changing crater conditions, forecast episodic eruptions, and mitigate impacts on communities and infrastructure.

Costa Rica — Poás Volcano and monitoring

Poás is an active stratovolcano in central Costa Rica rising to 2,708 m. It is part of the tectonically active Central America Volcanic Arc and has a well-documented eruptive record, with 39 eruptions reported since 1828, underscoring its role in regional volcanic hazard and geomorphological dynamics.

Observatorio Vulcanológico y Sismológico de Costa Rica (OVSICORI), housed at the National University of Costa Rica, provides dedicated research and monitoring of volcanic and seismic phenomena across the Central America Volcanic Arc. Its teams conduct continuous observation and study of volcanoes, earthquakes, and other tectonic processes, forming the primary scientific framework for understanding and managing hazards associated with volcanoes such as Poás.

Santa María (Guatemala), 1902

The 1902 eruption of Santa María was a brief but violently explosive event whose most intense detonations occurred within a concentrated two‑day interval. It expelled approximately 5.5 km³ of magma, an eruptive volume that ranks the episode among the largest volcanic releases of the twentieth century and produced extensive pyroclastic flows and significant atmospheric injection.

On the volcanic explosivity index the eruption is rated VEI‑6, reflecting its high magnitude and broad environmental effects. In scale and impact it has been closely compared to the 1991 Mount Pinatubo eruption, with Santa María’s 1902 event only marginally smaller than Pinatubo’s in overall ejecta and explosivity.

The eruption fundamentally altered the Santa María complex and initiated a prolonged phase of activity at the Santiaguito dome complex, which today stands as one of the world’s most persistently active volcanic centers. Santiaguito represents the ongoing post‑1902 expression of the system, producing frequent effusive and explosive episodes that continue to modify the landscape and pose local hazards.

Mexico — Trans‑Mexican Volcanic Belt

The Trans‑Mexican Volcanic Belt is a principal volcanic province extending roughly 900 km in a predominantly west–east orientation across central–southern Mexico. Its chain of volcanic centers owes its existence to subduction-related magmatism: the oceanic Cocos and Rivera plates descend beneath the Mexican margin, generating melts that feed the belt’s volcanoes and shape its long, linear distribution.

Among its edifices, Popocatépetl—located in the belt’s eastern sector—stands out both for elevation and activity. It is Mexico’s second‑highest peak after Pico de Orizaba and ranks among the nation’s most persistently active volcanoes, having produced more than twenty major eruptions since European contact in 1519. In contrast, the 1982 eruption of El Chichón demonstrated how eruptive risk can be concealed in apparently unremarkable terrain: the event produced a roughly 1‑km‑wide caldera that later contained an acidic crater lake and caused about 2,000 fatalities. El Chichón had been largely overlooked as a major hazard because it was heavily forested and lacked the conspicuous summit relief of neighboring nonvolcanic peaks, illustrating the potential for substantial volcanic threat where topographic prominence is absent.

United States (Cascadia and Alaskan systems)

The Cascade Volcanic Arc of the western United States comprises nearly twenty principal volcanoes and over 4,000 discrete vents of varied morphologies—stratovolcanoes, shields, lava domes, cinder cones and rarer tuyas—reflecting a complex, long-lived magmatic system. Volcanism along the arc initiated roughly 37 million years ago, but most current volcanic edifices are geologically young: the bulk formed within the past two million years and the tallest peaks have grown in the last 100,000 years. Holocene eruptions, including events within the last ~4,000 years, demonstrate that the arc remains an active hazard to Pacific Northwest communities and infrastructure.

Arc magmatism and regional seismicity are driven by subduction of the Gorda and Juan de Fuca plates beneath North America at the Cascadia subduction zone. This convergent margin is a broad, roughly 1,090 km (680 mi) fault system lying about 80 km offshore from northern California to Vancouver Island, with convergence at an oblique rate exceeding ~10 mm yr−1. Because the fault plane has a very large area, a full-margin rupture can generate megathrust earthquakes of magnitude ~9.0 or greater; geological and historical data indicate such an event occurred in 1700. Paleoseismic records reveal at least seven great ruptures in the past ~3,500 years, suggesting a recurrence interval on the order of 400–600 years.

Seismotectonic analyses resolve along-dip variations in fault behavior that govern rupture dynamics: an upper “locked” portion (extending roughly 60 km down-dip) accumulates elastic strain, beneath which a more deformable transition zone can still participate in rupture, and deeper down-dip sliding becomes largely aseismic. The Cascadia margin differs from many oceanic subduction zones in that a pronounced trench is not present; instead, accretionary processes and rapid sediment delivery from major rivers (notably the Fraser, Columbia and Klamath, which traverse the Cascades) have built an uplifted accretionary complex and obscured trench morphology.

Megathrust ruptures on Cascadia have consistently produced tsunamis. Coastal stratigraphic “scars” attest to local inundation, and contemporaneous tsunami records preserved in Japan confirm trans‑Pacific propagation of waves from past Cascadia earthquakes. Thus tsunami hazard is integral to the seismic risk posed by the subduction zone.

The 1980 Mount St. Helens eruption exemplifies the arc’s explosive potential and the rapid onset of volcanic catastrophes. Preceded by about two months of seismicity and phreatic activity associated with shallow magma intrusion and a pronounced north‑side bulge, the edifice failed catastrophically at 08:32 on 18 May 1980 when a triggering earthquake initiated sector collapse. The resulting depressurization produced an explosive lateral blast and high‑temperature pyroclastic flows that devastated the surrounding landscape and inundated Spirit Lake. With a Volcanic Explosivity Index of 5 and an erupted volume near 1.3 km3, this event was the most significant volcanic disaster in the contiguous United States in historical records.

Alaska constitutes the principal locus of North American volcanism and seismicity. The 1964 Good Friday earthquake there is the second-largest instrumentally recorded earthquake worldwide, and more than fifty Alaskan volcanic centers have erupted since about 1760. These volcanic systems are distributed across mainland Alaska and along the Aleutian island arc, contributing substantially to national geohazard exposure.

United States monitoring, research and warning for these volcanic and seismic threats are conducted by federal agencies, principally the United States Geological Survey (USGS) and the National Earthquake Information Center (NEIC), which operate networks and programs to detect unrest, characterize hazards and issue warnings.

Volcanism in British Columbia and Yukon (Canada)

British Columbia and Yukon lie within the Pacific Ring of Fire and contain a concentrated suite of volcanic centers and associated hazards. More than twenty individual volcanoes in this region have erupted during the Holocene, and the provincial/territorial volcanic province is customarily divided into five belts that reflect distinct tectonic settings and therefore differing magma chemistries, volcanic morphologies, eruption styles and temporal distributions.

Several volcanoes in western Canada record a direct plate‑boundary (subduction) origin. Six centers—Bridge River Cones, Mount Cayley, Mount Garibaldi, Garibaldi Lake area, Silverthrone Caldera and the Mount Meager massif—have the clearest tectonic link to subduction processes and are among the region’s most tectonically controlled volcanoes. The Garibaldi Volcanic Belt in southwestern British Columbia is the northern continuation of the Cascade Volcanic Arc and formed by subduction of the Juan de Fuca plate beneath North America; it contains Canada’s most explosively capable young volcanoes. Volcanic products in the Garibaldi Belt range from basalt to rhyolite and include calderas, cinder cones, stratovolcanoes and isolated lava masses. Repeated continental and alpine glaciations have overprinted eruptive deposits, producing complex stratigraphic records of interactions among magma composition, topography and ice cover.

The Mount Meager massif is the Garibaldi Belt’s most recent large explosive source: a catastrophic eruption about 2,350 years ago produced an ash column estimated to reach ~20 km and is comparable in scale and style to the 1980 Mount St. Helens event. Topographically, the massif (viewed from near Pemberton) comprises adjacent summits including Capricorn Mountain, Mount Meager and Plinth Peak, and its terrain links volcanic highlands with populated valleys of southwestern British Columbia. Principal Garibaldi centers also include the Bridge River Cones, Mount Cayley, Mount Fee, Mount Garibaldi, Mount Price, the Squamish Volcanic Field and numerous smaller edifices.

Not all regional volcanism is subduction‑related. The Northern Cordilleran Volcanic Province (NCVP) comprises rift‑related volcanic centers generated by continental extension rather than by plate‑interface processes; geologists commonly regard the NCVP as a rift gap in the Ring of Fire between the Cascade arc to the south and the Aleutian/Alaskan arc to the north. The Chilcotin Group, a north–south belt parallel to the Garibaldi Belt, is interpreted as the product of back‑arc extension behind the Cascadia subduction system; most Chilcotin eruptions date to the Miocene–Pliocene (6–10 Ma and 2–3 Ma), with some younger Pleistocene flows. Representative Chilcotin features include Mount Noel, the Clisbako Caldera Complex, Lightning Peak, Black Dome Mountain and extensive Pliocene–Pleistocene lava fields. The Alert Bay Volcanic Belt on northern Vancouver Island, composed of basaltic to rhyolitic volcanics and related hypabyssal intrusions, likely formed in a subduction‑influenced margin between the Explorer and Juan de Fuca plates during the Pliocene–Pleistocene; no Holocene eruptions are documented and current evidence suggests activity there has largely ceased.

Activity status and hazards in Canada are heterogeneous. No volcanoes are erupting at present, but several individual cones, fields and centers are classed as potentially active. Many conspicuous volcanic mountains in populated parts of British Columbia are dormant, with their most recent eruptions in the Pleistocene or Holocene; some sites host thermal springs and exhibit ongoing seismicity that may reflect magmatic or hydrothermal processes. Instrumental seismic records since 1975 have associated earthquake swarms and other seismicity with a number of British Columbia volcanoes—including both the six subduction‑linked centers and intraplate areas such as the Wells Gray–Clearwater volcanic field—demonstrating continued tectono‑volcanic interaction and the value of geophysical monitoring.

Seismic hazard in the region is not restricted to volcanic sources. The active Queen Charlotte Fault off Haida Gwaii has produced large historical earthquakes (M ~7 in 1929, M 8.1 in 1949—Canada’s largest recorded earthquake—and M 7.4 in 1970), underscoring a significant earthquake and tsunami potential distinct from volcanic risk.

Natural Resources Canada, through its Public Safety Geoscience Program, supports research, monitoring and hazard assessment for volcanoes, earthquakes, tsunamis, landslides and related hazards in western Canada. That scientific basis underpins ongoing efforts in geophysical surveillance, risk reduction and emergency preparedness across the region’s varied volcanic and tectonic provinces.

Kambalny is an active volcano on the Kamchatka Peninsula of the Russian Far East and forms part of that peninsula’s extensive volcanic system. Kamchatka, bounded by the Pacific Ocean to the east and the Sea of Okhotsk to the west, ranks among the world’s most volcanically active regions, containing some 20 historically active volcanoes. Immediate offshore subduction at the Kuril–Kamchatka Trench—a 10,500‑metre-deep convergent margin—driven by the Pacific Plate is the principal mechanism supplying magma and thermal energy to the arc. Volcanism on Kamchatka expresses itself in diverse forms, from large stratovolcanoes and shield edifices to Hawaiian‑style fissure eruptions and geothermal features such as geysers, reflecting a wide range of eruptive styles and heat‑transfer processes. The arc’s volcanic edifices are organized into two principal belts, with the most recent eruptive activity concentrated in the eastern belt. That eastern belt begins in the north with the tectonically important Shiveluch complex at the junction of the Aleutian and Kamchatka arcs, and continues south through the Klyuchi group—notably the twin cones Kliuchevskoi and Kamen—and the Tolbachik and Ushkovsky complexes among other large stratovolcanoes. By contrast, Ichinsky is the sole historically active volcano of the more westerly central belt. The eastern belt extends to the peninsula’s southern tip and continues into the Kuril island arc, which itself contains 32 historically active volcanoes.

Japan occupies a zone of pronounced crustal instability where the Pacific and Philippine Sea plates descend beneath the Eurasian margin, making the archipelago one of the most volcanically and seismically active regions on Earth and hosting roughly 10% of the planet’s active volcanoes. Seismicity is pervasive: Japan records on the order of 1,500 earthquakes annually, with magnitudes in the 4–6 range occurring with some regularity, minor tremors felt almost daily in parts of the country, and less frequent but potentially catastrophic great earthquakes. Historically devastating events include the 1923 Great Kantō quake (≈130,000 fatalities), the 1995 Great Hanshin earthquake (6,434 fatalities), and the magnitude‑9.0 Tōhoku earthquake of 11 March 2011 — Japan’s largest recorded quake and, by USGS ranking, the fifth largest instrumentally recorded worldwide. In addition to ground shaking, large undersea shocks generate tsunamis that pose a persistent coastal hazard.

Volcanic behavior in Japan is exemplified at both local and national scales. Mount Bandai, on the north shore of Lake Inawashiro, is a complex of overlapping stratovolcanoes whose principal edifice, O‑Bandai, occupies a horseshoe‑shaped caldera produced by a collapse about 40,000 years ago. That collapse generated the Okinajima debris avalanche and was accompanied by a Plinian eruption. During the past 5,000 years Bandai has experienced four major phreatic eruptions, including historically recorded events in 806 and 1888. Morphologically Bandai appears conical from the south, but much of its northern flank was removed during the 1888 Ko‑Bandai collapse, which buried villages and formed several lakes; eyewitness accounts describe a week of seismic unrest culminating in a large earthquake and a series of explosive episodes, the final blast directed almost horizontally to the north. The 1888 collapse has been likened in character to the May 18, 1980, eruption of Mount St. Helens.

Mount Fuji, Japan’s highest and most emblematic volcano, is a postglacial stratovolcano built atop an older assemblage of overlapping volcanoes, whose remnants impart irregularities to Fuji’s external form. The growth history of the younger Fuji is well resolved: voluminous summit and flank lava flows between about 11,000 and 8,000 years ago produced roughly four‑fifths of its present volume; from 8,000 to 4,500 years ago activity was dominated by less voluminous explosive eruptions; a renewed phase of major lava effusion occurred from 4,500 to 3,000 years ago; and from 3,000 to 2,000 years ago summit eruptions prevailed, after which flank‑vent activity became more common alongside intermittent major explosive events, subordinate lava flows, and small pyroclastic flows. Geomorphically, extensive basaltic flows from the summit and more than 100 flank cones and vents impeded drainage against the Tertiary Misaka Mountains to the north, producing the Fuji Five Lakes. The most recent eruption in 1707 deposited andesitic pumice and opened a large crater on the east flank; minor volcanic unrest remains possible in the future.

Philippines — volcanic activity and hazards

The volcanic provinces of the Philippine archipelago comprise numerous active centers whose eruptive styles, histories and summit-to-flank landforms generate a wide suite of hazards. Steep summit craters, sharp flanks, radial ravines and crater lakes interact with basaltic–andesitic to more silicic magmas to produce explosive ash emissions, pyroclastic density currents, effusive lava, lahars and phreatic or phreatomagmatic blasts. Where monitoring and forecasting have provided timely warnings, large-scale evacuations have substantially reduced fatalities; conversely, abrupt eruptions have occasioned significant loss of life and mass displacement.

The 1991 eruption of Mount Pinatubo exemplifies a high-consequence explosive event in the Philippines. Its climactic phase ranks among the largest eruptions of the twentieth century. Scientific forecasting and coordinated evacuations removed many residents from danger, yet pyroclastic flows, thick tephra deposits and subsequent rain-triggered lahars inflicted widespread destruction on populated valleys and destroyed thousands of houses as remobilized material choked drainage systems.

Mayon Volcano, the country’s most active cone, combines a steep upper profile (average slope 35–40°) and a small summit crater with an eruptive record extending back to the early 17th century. Its basaltic–andesitic magmas produce a spectrum of activity from Strombolian to basaltic Plinian, typically from a central conduit but also generating long-running lava flows. Pyroclastic currents and mudflows commonly descend numerous ravines radiating from the summit (roughly forty channels are noted), repeatedly threatening densely settled lowlands; photographic and historical records document abrupt destructive eruptions such as that of September 1984.

Taal Volcano illustrates hazards associated with magmatic interaction with surface water. With more than thirty documented eruptions since the sixteenth century, its 1911 event produced heavily altered, sulfur-rich tephra and caused over a thousand fatalities. Episodes between 1965 and 1977 were characterized by violent phreatic and phreatomagmatic behavior driven by intimate magma–lake interaction. After decades of relative quiescence, renewed unrest beginning in the 1990s—marked by heightened seismicity, ground fracturing and mud geysering—culminated in an eruption in January 2020, underscoring the system’s persistent instability.

Kanlaon, the most active volcanic center in the central Philippines, has erupted repeatedly since the mid‑nineteenth century. Its activity is dominated by small- to moderate-sized phreatic explosions that typically produce localized ashfall, but unexpected events can be lethal or highly disruptive: an unforeseen summit eruption in August 1996 killed three climbers among a party on the mountain, and a June 2024 eruption displaced over a thousand residents.

Across these centres, hazard processes share common controls and outcomes: (1) explosive eruptions produce pyroclastic flows and widespread ashfall; (2) central-vent eruptions can emit lava that travels far downslope; (3) unconsolidated tephra is readily remobilized by rainfall into destructive lahars that affect drainage networks for years after eruptions; (4) magma–water interaction yields abrupt phreatic and phreatomagmatic blasts where crater lakes or groundwater are present; and (5) geomorphic focusing of flows through radial ravines amplifies impacts on lowland settlements. The combination of these physical processes with high population densities in coastal and valley areas makes volcanic risk a recurring and multi‑dimensional challenge for the Philippine archipelago.

Indonesia sits at the convergence of two major tectonic systems—the Pacific Ocean’s Ring of Fire and the Alpide belt, the latter stretching from Southeast Asia westward through Southwest Europe—which concentrates volcanic activity across the archipelago. This juxtaposition yields two principal tectonic regimes: subduction of the Pacific plate and attendant microplates beneath eastern island groups, and northward subduction in the Indian Ocean beneath the western Sunda Arc.

The eastern islands (notably Sulawesi; most of the Lesser Sundas excluding Bali, Lombok, Sumbawa and Sangeang; Halmahera; the Banda and Sangihe Islands) are tectonically linked to Pacific-plate or related microplate subduction and are thereby aligned with the Ring of Fire volcanic province. By contrast, the western chain—embodied by the Sunda Arc (including Sumatra) and volcanic centers such as Krakatoa, Merapi, Tambora and Toba—derives its volcanism from Indian Ocean subduction north of the arc and is typically associated with the Alpide tectonic framework.

This duality produces a complex mosaic of volcanic arcs and provinces across Indonesia and accounts for the country’s high density of major volcanoes distributed between eastern Pacific-driven arcs and western Alpide-associated arcs. Classification varies by audience: popular media and some geoscientists often subsume western Indonesian volcanoes within the Ring of Fire, whereas many specialists distinguish the western islands as part of the Alpide system to reflect their distinct tectonic control.

Islands in the southwest Pacific Ocean — tectonic setting

Papua New Guinea lies at a complex junction between the northward-moving Australian Plate and the Pacific Plate to its northeast, where relative motion is accommodated by an array of smaller plates and crustal blocks. Interaction among these plates—principally subduction of oceanic lithosphere, arc‑forming collision, and strike‑slip faulting—drives intense seismicity, widespread volcanism, and rapid crustal deformation. The northward push of the Australian Plate produces crustal shortening and uplift of New Guinea’s central highlands (the Maoke Mountains/Central Cordillera), while Pacific Plate motions generate volcanic arcs and deep trenches in the adjacent western Pacific.

Surrounding microplates form a tightly segmented boundary zone that concentrates diverse tectonic processes in a relatively small area. To the north and west, the Caroline and Banda Sea plates participate in accommodating Pacific–Australian convergence and help shape deformation north of New Guinea and in eastern Indonesia. The Woodlark Plate to the east and southeast is characterized by localized extension and active seafloor spreading in the Woodlark Basin. Smaller crustal blocks such as the Bird’s Head (Vogelkop) and Maoke plates control localized faulting, uplift and the internal deformation of the island’s mountainous spine. The Solomon Sea Plate and the paired North and South Bismarck plates underlie the Solomon and Bismarck seas and mediate strain transfer that drives the Solomon Islands arc and tectonics around New Britain. The Manus microplate in the Manus Basin further contributes to the mosaic of rotating blocks, basin formation and focused seismicity. Collectively, these interacting plates produce subduction polarity reversals, arc volcanism, back‑arc spreading, microplate rotations and rapid mountain building within a compact southwest Pacific realm.

West Mata is a submarine volcano situated in the southwestern Pacific between the island chains of Samoa and Tonga; its documented eruptive activity in 2010 highlights the prevalence of active volcanism in this corridor. Because eruptive processes occur below sea level, magmatic emplacement and fragmentation interact directly with high‑pressure seawater, promoting rapid thermal quenching of erupted material and producing characteristic submarine lithologies such as glassy hyaloclastite and pillow lavas rather than the convective ash plumes typical of subaerial eruptions.

The occurrence of West Mata reflects the broader tectonic regime of the Samoa–Tonga region, where subduction-related dynamics, arc volcanism and back‑arc basin extension together generate frequent magmatism and create loci for submarine volcanic centers. Eruptions in this setting play a constructive and reworking role on the seafloor, producing new volcanic substrates and locally altering bathymetry.

Submarine eruptions at West Mata and similar sites produce oceanographically and geochemically significant phenomena: hydrothermal venting and buoyant chemical plumes, localized heating of the water column, release of gases and dissolved metals, and rapid modification of seafloor morphology and substrate composition. These episodic inputs materially affect nearby benthic and pelagic ecosystems and provide in situ opportunities to study arc–back‑arc magmatism, vent biogeochemistry and early stages of seafloor formation.

Because the volcano is remote and submerged, detecting and characterizing eruptive events requires specialized marine techniques rather than conventional aerial or ground observations. Oceanographic ship surveys, targeted seafloor and water‑column sampling, hydroacoustic monitoring and direct observation using remotely operated vehicles or manned submersibles are essential for documenting eruptive activity and its products. From a geohazard and navigation perspective, submarine eruptions may produce transient hazards—such as gas‑charged plumes or floating volcanic fragments—and can rapidly change local bathymetry, complicating risk assessments for nearby island communities and maritime traffic.

New Zealand’s volcanic landscape is dominated by intense, predominantly silicic volcanism concentrated on the North Island. The country contains the world’s most concentrated assemblage of youthful rhyolitic volcanoes; extensive, voluminous sheets of tuff blanket large areas of the North Island, recording repeated, widespread explosive rhyolitic eruptions and extensive tephra deposition. Over the last ~1.6 million years the Taupō Volcanic Zone (TVZ) has been the primary focus of Quaternary volcanism in New Zealand, representing the principal locus of recent large-volume silicic activity.

Within the TVZ, Mount Ruapehu at its southern extremity is one of New Zealand’s most actively erupting volcanoes, with a history of volcanism extending at least 250,000 years. Major explosive episodes have recurred at roughly half-century intervals in recorded history (notably 1895, 1945 and 1995–96), while numerous smaller eruptions—more than 60 since 1945—have produced minor ash falls and lahars that have intermittently damaged infrastructure such as ski fields. Ruapehu’s summit hosts a warm, acid crater lake sustained by snowmelt; eruptive processes can evacuate the lake and the emplacement of tephra dams at the lake outlet creates a recurrent geohazard whereby catastrophic dam collapse during lake refill generates large lahars. The most severe lahar disaster in New Zealand’s recorded history, the Tangiwai event of 24 December 1953, occurred when a tephra-dam–induced lahar destroyed a rail bridge, killing 151 people. In response to such hazards, an Eruption–Lahar Warning System (ERLAWS) was installed on Ruapehu in 2000 to detect tephra-dam failure and provide early warning.

Beyond the TVZ, volcanism is spatially varied. The Auckland volcanic field, beneath a major metropolitan area on the northern North Island, comprises at least 40 discrete volcanic centers that produced a mix of explosive maar/crater structures, scoria cones and lava flows; although presently quiescent, the field is considered likely to produce future eruptions on timescales of hundreds to thousands of years. Rangitoto Island is the field’s youngest and most voluminous Holocene eruptive center, erupting about 600 years ago and emplacing roughly 2.3 km3 of lava—one of the largest single Holocene lava volumes in the field. Historically recorded eruptions elsewhere include Whakaari/White Island (first historically dated in 1826) and the large, widely documented eruption of Mount Tarawera in 1886, which stands as New Zealand’s largest historical eruption.

Offshore and in regional context, the marine area north of the North Island is characterized by an archipelago of submarine volcanic edifices and emergent islets, including some 16 identified submarine volcanoes that contribute to New Zealand’s complex offshore volcanic morphology. Prominent subaerial stratovolcanoes such as Mount Taranaki (Egmont) form part of the country’s suite of major volcanic cones and are significant regional geomorphic landmarks. Collectively, these elements—intense rhyolitic volcanism, an active TVZ with hazardous crater-lake dynamics, metropolitan volcanic fields, historical explosive events, offshore seamounts, and major stratovolcanoes—define New Zealand’s distinctive and diverse volcanic regime within the wider Ring of Fire.

Andosols (Andisols) in the Ring of Fire

Andosols, also called andisols, are a distinct soil order that develops predominantly from the weathering of volcanic ash and other pyroclastic deposits rather than from in situ bedrock alteration. A defining characteristic is their high content of volcanic glass derived from fresh ash; this glassy material strongly affects particle size distribution, porosity, chemical reactivity and the soil’s pedogenic pathways, producing properties that differ markedly from soils formed on non‑volcanic parent materials.