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Volcanic cone
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Mayon in the Philippines has a symmetrical volcanic cone.

Volcanic cones are among the simplest volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and size of the fragments ejected during the eruption. Types of volcanic cones include stratocones, spatter cones, tuff cones, and cinder cones.[1][2]

Stratocone

[edit]
Main article: Stratovolcano
Osorno volcano in Chile is an example of a well-developed stratocone.

Stratocones are large cone-shaped volcanoes made up of lava flows, explosively erupted pyroclastic rocks, and igneous intrusives that are typically centered around a cylindrical vent. Unlike shield volcanoes, they are characterized by a steep profile and periodic, often alternating, explosive eruptions and effusive eruptions. Some have collapsed craters called calderas. The central core of a stratocone is commonly dominated by a central core of intrusive rocks that range from around 500 meters (1,600 ft) to over several kilometers in diameter. This central core is surrounded by multiple generations of lava flows, many of which are brecciated, and a wide range of pyroclastic rocks and reworked volcanic debris. The typical stratocone is an andesitic to dacitic volcano that is associated with subduction zones. They are also known as either stratified volcano, composite cone, bedded volcano, cone of mixed type or Vesuvian-type volcano.[1][2]

Spatter cone

[edit]
Puʻu ʻŌʻō, a cinder-and-spatter cone on Kīlauea, Hawaiʻi

A spatter cone is a low, steep-sided hill or mound that consists of welded lava fragments, called spatter, which has formed around a lava fountain issuing from a central vent. Typically, spatter cones are about 3–5 meters (9.8–16.4 ft) high. In case of a linear fissure, lava fountaining will create broad embankments of spatter, called spatter ramparts, along both sides of the fissure. Spatter cones are more circular and cone shaped, while spatter ramparts are linear wall-like features.[1][3][4]

Spatter cones and spatter ramparts are typically formed by lava fountaining associated with mafic, highly fluid lavas, such as those erupted in the Hawaiian Islands. As blobs of molten lava, spatter, are erupted into the air by a lava fountain, they can lack the time needed to cool completely before hitting the ground. Consequently, the spatter are not fully solid, like taffy, as they land and they bind to the underlying spatter as both often slowly ooze down the side of the cone. As a result, the spatter builds up a cone that is composed of spatter either agglutinated or welded to each other.[1][3][4]

Tuff cones

[edit]
See also: Phreatomagmatic eruption
Koko Crater is a tuff cone that is part of the Honolulu Volcanic Series.

A tuff cone, sometimes called an ash cone, is a small monogenetic volcanic cone produced by phreatic (hydrovolcanic) explosions directly associated with magma brought to the surface through a conduit from a deep-seated magma reservoir. They are characterized by high rims that have a maximum relief of 100–800 meters (330–2,620 ft) above the crater floor and steep slopes that are greater than 25 degrees. They typically have a rim to rim diameter of 300–5,000 meters (980–16,400 ft). A tuff cone consists typically of thick-bedded pyroclastic flow and surge deposits created by eruption-fed density currents and bomb-scoria beds derived from fallout from its eruption column. The tuffs composing a tuff cone have commonly been altered, palagonitized, by either its interaction with groundwater or when it was deposited warm and wet. The pyroclastic deposits of tuff cones differ from the pyroclastic deposits of spatter cones by their lack or paucity of lava spatter, smaller grain-size, and excellent bedding. Typically, but not always, tuff cones lack associated lava flows.[2][5]

A tuff ring is a related type of small monogenetic volcano that is also produced by phreatic (hydrovolcanic) explosions directly associated with magma brought to the surface through a conduit from a deep-seated magma reservoir. They are characterized by rims that have a low, broad topographic profiles and gentle topographic slopes that are 25 degrees or less. The maximum thickness of the pyroclastic debris comprising the rim of a typical tuff ring is generally thin, less than 50 meters (160 ft) to 100 meters (330 ft) thick. The pyroclastic materials that comprise their rim consist primarily of relatively fresh and unaltered, distinctly and thin-bedded volcanic surge and air fall deposits. Their rims also can contain variable amounts of local country rock (bedrock) blasted out of their crater. In contrast to tuff cones, the crater of a tuff ring generally has been excavated below the existing ground surface. As a result, water commonly fills a tuff ring's crater to form a lake once eruptions cease.[2][5]

Both tuff cones and their associated tuff rings were created by explosive eruptions from a vent where the magma is interacting with either groundwater or a shallow body of water as found within a lake or sea. The interaction between the magma, expanding steam, and volcanic gases resulted in the production and ejection of fine-grained pyroclastic debris called ash with the consistency of flour. The volcanic ash comprising a tuff cone accumulated either as fallout from eruption columns, from low-density volcanic surges and pyroclastic flows, or combination of these. Tuff cones are typically associated with volcanic eruptions within shallow bodies of water and tuff rings are associated with eruptions within either water saturated sediments and bedrock or permafrost.[2][5][6]

Next to spatter (scoria) cones, tuff cones and their associated tuff rings are among the most common types of volcanoes on Earth. An example of a tuff cone is Diamond Head at Waikīkī in Hawaiʻi.[2] Clusters of pitted cones observed in the Nephentes/Amenthes region of Mars at the southern margin of the ancient Utopia impact basin are currently interpreted as being tuff cones and rings.[7]

Cinder cone

[edit]
Main article: Cinder cone
Cinder cone
Parícutin is a large cinder cone in Mexico.

Cinder cones, also known as scoria cones and less commonly scoria mounds, are small, steep-sided volcanic cones built of loose pyroclastic fragments, such as either volcanic clinkers, cinders, volcanic ash, or scoria.[1][8] They consist of loose pyroclastic debris formed by explosive eruptions or lava fountains from a single, typically cylindrical, vent. As the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as either cinders, clinkers, or scoria around the vent to form a cone that often is noticeably symmetrical; with slopes between 30 and 40°; and a nearly circular ground plan. Most cinder cones have a bowl-shaped crater at the summit.[1] The basal diameters of cinder cones average about 800 meters (2,600 ft) and range from 250 to 2,500 meters (820 to 8,200 ft). The diameter of their craters ranges between 50 and 600 meters (160 and 1,970 ft). Cinder cones rarely rise more than 50–350 meters (160–1,150 ft) or so above their surroundings.[2][9]

Cinder cones most commonly occur as isolated cones in large basaltic volcanic fields. They also occur in nested clusters in association with complex tuff ring and maar complexes. Finally, they are also common as parasitic and monogenetic cones on complex shield and stratovolcanoes. Globally, cinder cones are the most typical volcanic landform found within continental intraplate volcanic fields and also occur in some subduction zone settings as well. Parícutin, the Mexican cinder cone which was born in a cornfield on February 20, 1943, and Sunset Crater in Northern Arizona in the US Southwest are classic examples of cinder cones, as are ancient volcanic cones found in New Mexico's Petroglyph National Monument.[2][9] Cone-shaped hills observed in satellite imagery of the calderas and volcanic cones of Ulysses Patera,[10] Ulysses Colles[11] and Hydraotes Chaos[12] are argued to be cinder cones.

Cinder cones typically only erupt once like Parícutin. As a result, they are considered to be monogenetic volcanoes and most of them form monogenetic volcanic fields. Cinder cones are typically active for very brief periods of time before becoming inactive. Their eruptions range in duration from a few days to a few years. Of observed cinder cone eruptions, 50% have lasted for less than 30 days, and 95% stopped within one year. In case of Parícutin, its eruption lasted for nine years from 1943 to 1952. Rarely do they erupt either two, three, or more times. Later eruptions typically produce new cones within a volcanic field at separation distances of a few kilometers and separate by periods of 100 to 1,000 years. Within a volcanic field, eruptions can occur over a period of a million years. Once eruptions cease, being unconsolidated, cinder cones tend to erode rapidly unless further eruptions occur.[2][9]

Rootless cones

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Main article: Rootless cone

Rootless cones, also called pseudocraters, are volcanic cones that are not directly associated with a conduit that brought magma to the surface from a deep-seated magma reservoir. Generally, three types of rootless cones, littoral cones, explosion craters, and hornitos are recognized. Littoral cones and explosion craters are the result of mild explosions that were generated locally by the interaction of either hot lava or pyroclastic flows with water. Littoral cones typically form on the surface of a basaltic lava flow where it has entered into a body of water, usually a sea or ocean. Explosion craters form where either hot lava or pyroclastic flows have covered either marshy ground or water-saturated ground of some sort. Hornitos are rootless cones that are composed of welded lava fragments and were formed on the surface of basaltic lava flows by the escape of gas and clots of molten lava through cracks or other openings in the crust of a lava flow.[1][9][13]

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Volcanic cone

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A volcanic cone is a hill or mountain with a conical shape formed by the accumulation of volcanic material, such as lava fragments, , and pyroclastic debris, around a central vent during eruptions. These structures typically result from or effusive volcanic activity and can vary widely in size, from small mounds a few meters high to large peaks exceeding 4,000 meters. Unlike broad shield volcanoes, volcanic cones often feature steep slopes due to the loose, fragmented nature of their building materials. Volcanic cones are classified into several types based on their composition, formation process, and eruption style. Cinder cones, the simplest and most common variety, are built from pea-sized to gravel-sized cinders ejected during moderately explosive eruptions of basaltic or andesitic , forming steep-sided piles rarely taller than 300 meters with a bowl-shaped at the summit. Composite cones, also known as stratovolcanoes, are larger and more complex, constructed through alternating layers of viscous lava flows, , and pyroclastic deposits over multiple eruptive cycles, resulting in symmetrical, towering edifices up to 8,000 feet high. Other subtypes include spatter cones, small (1-5 meters high) steep mounds formed by the aggregation of molten lava blobs from low-viscosity fountains, and cones, which arise from explosive interactions between and , producing steep-sided 100-300 meters tall filled with consolidated . Types such as cinder, spatter, and cones are often monogenetic, meaning they typically experience a single eruptive episode lasting days to years before becoming dormant, though some contribute to broader landscapes in volcanic fields. In contrast, stratovolcanoes are typically polygenetic. Notable examples include in , a that emerged in a cornfield in 1943 and grew to 424 meters in under a decade, and Diamond Head in , a cone formed about 200,000 years ago. Volcanic cones play a key role in understanding volcanic hazards, as their instability can lead to landslides, and they serve as indicators of underlying composition and tectonic settings.

Overview

Definition

A volcanic cone is a hill-shaped produced by the accumulation of volcanic , such as , cinders, and lava fragments, that pile up around a central vent during eruptions, typically forming a conical or dome-like structure. This buildup occurs as materials are ejected ballistically from the vent and settle due to gravity, creating a mound centered on the eruption site. Key characteristics of volcanic cones include steep slopes, often ranging from 20 to 35 degrees, which result from the angle of repose of the loose pyroclastic materials; a central or vent at the ; and heights varying from tens of meters for small cones to over a thousand meters for larger edifices. These features distinguish volcanic cones as localized, mound-like structures rather than expansive plateaus. The concept of volcanic cones was first systematically described in geological literature during the by pioneers such as , who in 1850 detailed their structure and growth in observations on Mount Etna and other sites, emphasizing accumulative processes over catastrophic formation theories. Modern understandings have been refined since the mid-20th century with the advent of theory, which contextualizes cones within global tectonic settings like zones. Unlike broad, low-relief volcanoes formed by fluid lava flows, volcanic cones exhibit steeper profiles and more confined shapes due to their construction from coarser, fragmented .

Geological Significance

Volcanic cones serve as natural laboratories for volcanologists, enabling detailed investigations into composition, eruption dynamics, and associated tectonic settings through their accessible deposits and structural features. These landforms allow researchers to analyze variations in volcanic processes, such as the fragmentation of low-viscosity s and the evolution of monogenetic eruptions, providing insights into broader crustal and mantle interactions. By examining the morphology and internal architecture of cones, scientists can track erosional processes and reconstruct short-term volcanic histories, contributing to models of volcanic field development. The hazard implications of volcanic cones are significant, as they pose risks from explosive eruptions, lahars, and ash falls that can affect surrounding populations and infrastructure. Monitoring efforts typically involve seismic sensors to detect ground deformation and , alongside gas sensors measuring emissions like to forecast eruptive activity and mitigate threats. Such integration helps in assessing the potential for pyroclastic flows confined to cone flanks and broader dispersal, informing evacuation and in volcanic regions. Ecologically, volcanic cones contribute to fertile soils enriched by weathered ash and lava, supporting in regions with high content, such as on nutrient-rich andosols. Economically, these features enable extraction from underlying heat sources, powering and heating systems in volcanic terrains. Scientifically, the layered deposits of volcanic cones preserve stratigraphic records of past eruptions, offering valuable data for by linking layers to global climate perturbations and eruption timelines. These archives aid in developing eruption forecasting models through analysis of deposit thickness, composition, and distribution, enhancing predictions of future volcanic behavior.

Formation Processes

Primary Mechanisms

Volcanic cones primarily form through the ascent of from depth, driven by forces arising from the contrast between the ascending and the surrounding crustal rocks. Mantle-derived , typically basaltic in composition, rises due to its lower compared to the overlying , facilitated by pressure gradients that propel it upward through pre-existing fractures or newly formed dikes in the crust. This process culminates in venting at the surface, where the breaches to form a central vent, often initiating cone construction. The ascent rate can vary from meters per day in slow intrusions to kilometers per hour in rapid eruptions, influenced by the permeability of the conduit and the 's rheological properties. Eruption styles critical to cone formation involve ballistic ejection of fragmented material during Strombolian or Vulcanian events, characterized by intermittent explosions that propel pyroclasts into the air. In Strombolian eruptions, gas bubbles burst near the surface, ejecting molten fragments in discrete bursts up to several hundred meters high, following parabolic trajectories determined by initial velocity and . Vulcanian eruptions are more violent, involving plug disruption that launches at higher speeds, contributing to steeper initial cone slopes through rapid accumulation around the vent. These dynamics result in the symmetric, conical morphology typical of many volcanic s. Cone growth proceeds in distinct phases, beginning with initial vent clearing explosions that remove obstructing material and establish the eruptive conduit, often within the first hours or days of activity. This is followed by sustained buildup, where repeated ejections accumulate fragments to form the cone's edifice, with height development closely tied to ejection velocities ranging from 10 to 100 m/s, which dictate the dispersal range and settling pattern of materials. Over time, the cone's structure stabilizes as eruption intensity wanes, though breaching or slumping can occur if asymmetric growth develops. Key influencing factors include the magma's dissolved gas content, typically 1-6% volatiles by weight (primarily and ), and its , which together govern eruption explosivity. Higher volatile concentrations promote bubble expansion and fragmentation upon decompression, enhancing ballistic ejection, while low- magmas allow efficient gas escape and milder activity; conversely, viscous magmas trap gases, leading to more venting essential for cone formation. These properties vary with composition, with types favoring less explosive styles conducive to prolonged cone building.

Eruptive Materials and Buildup

Volcanic cones are constructed primarily from pyroclastic materials ejected during eruptions, including , , and bombs. Scoria consists of vesicular fragments of basaltic to andesitic composition, formed by the rapid cooling of with trapped gas bubbles, while comprises fine particles less than 2 mm in diameter, and bombs are larger, rounded greater than 64 mm that solidify in flight. In some instances, effusive lava flows contribute to the buildup, particularly where eruptions transition from to effusive phases, adding consolidated layers to the cone's structure. The accumulation of these materials occurs through a layering process, with alternating beds of coarse fragments such as and bombs interbedded with finer deposits. This stratification develops from repeated eruptive pulses, where coarser particles settle closer to the vent via ballistic trajectories, and finer is carried farther by eruption columns before falling out. sorting is influenced by factors like ejection and wind direction, leading to banded layers where coarse and fine materials alternate due to varying atmospheric transport. Stability of the is governed by the angle of repose of the unconsolidated pyroclastics, typically ranging from 30 to 35 degrees, which dictates the initial steepness and overall form. This angle represents the maximum at which loose remains without sliding, providing resistance to minor but rendering cones vulnerable to rapid degradation from , rain, or seismic activity over time. Volumetric buildup proceeds radially from the central vent, with materials accumulating symmetrically to form a conical shape, where height and base diameter ratios often approximate 1:4 to 1:6 for mature cones. The total volume can be estimated for idealized structures using the geometric for a : V=13πr2hV = \frac{1}{3} \pi r^2 h where rr is the base and hh is the , allowing geologists to quantify erupted material based on field measurements of these dimensions.

Types of Volcanic Cones

Cinder Cones

Cinder cones represent the simplest form of monogenetic volcanic structures, built primarily from dark and cinder fragments ejected during mild explosive eruptions of , gas-rich . These pyroclastic materials consist of basaltic to basaltic-andesite lava that fragments in the air due to rapid gas expansion, solidifying into porous, vesicular that accumulates around a single vent. Unlike more complex volcanoes, cinder cones form solely through this buildup, with occasional associated lava flows emerging once initial explosivity wanes. Morphologically, cinder cones exhibit symmetrical, conical shapes with steep sides determined by the angle of repose of loose pyroclastics, typically sloping between 25 and 32 degrees. Their heights generally range from 30 to 300 meters, rarely exceeding 1,000 feet, and they often feature a bowl-shaped summit . These cones frequently occur in clusters or alignments within monogenetic volcanic provinces, reflecting underlying tectonic controls such as fissures or dike swarms. Eruptive activity at cinder cones is short-lived and confined to a single cycle, lasting from months to a few years, after which the vent typically becomes inactive. Post-eruption, the cones are subject to rapid by wind, water, and , often resulting in breached craters on one side where material slumps or washes away. A classic example is in , which grew to 424 meters (1,391 feet) in height over nine years from 1943 to 1952 before ceasing activity. Cinder cones are globally prevalent in rift zones and volcanic fields, where basaltic dominates. They are particularly common along divergent plate boundaries and intraplate hotspots, comprising the majority of vents in such settings; for instance, in the of , most of the over 600 volcanic features are cinder cones. This distribution underscores their role in monogenetic volcanism, with concentrations often aligned along rift-related fractures.

Spatter Cones

Spatter cones are volcanic landforms produced during effusive eruptions characterized by low-explosivity fire fountaining, where molten basaltic lava is ejected in fountains and the resulting spatter partially welds upon landing to build accumulations around vents. These structures form primarily from Hawaiian-style eruptions along s, in which hot, fluid fragments of lava—known as spatter or agglutinate—pile up and fuse due to their plasticity, creating ramparts or discrete mounds without significant fragmentation. The process involves minimal gas-driven disruption, allowing the ejecta to remain cohesive and adhere, often elongating the cones parallel to the underlying eruptive . Physically, spatter cones exhibit low, broad profiles with heights typically ranging from 1 to 10 meters, though some ramparts can reach up to 7 meters, and they are composed of clastogenic lavas featuring vesicular textures from trapped gases. These cones often display steep-sided, asymmetrical shapes due to the directional deposition of spatter, with fluidal clasts that show high degrees of and compaction, resulting in dense layers with densities around 1.5 g/cm³. Vesicularity in the spatter is moderate, averaging about 63%, reflecting variable during fountain heights of 10 to 500 meters. The eruptive conditions favoring spatter cone formation involve basaltic with low , typically 10–100 Pa·s, which enables fluid flow and reduces fragmentation during fountaining. This gas-poor, composition promotes effusive behavior rather than violent explosions, with fountains driven by moderate volatile content that propels lava before it cools and welds. Such conditions are common in settings, as exemplified by the spatter contributions to the Pu‘u ‘Ö‘ö cone during the 1983–1986 episodes of volcano, where fountaining up to 470 meters built agglutinated layers integral to the structure. Spatter cones are closely associated with surrounding lava flows, often feeding pāhoehoe or ‘a‘ā flows that extend from the vents, and can form perched features on older flows or contribute to kipukas by encircling and isolating pre-existing terrain. These landforms highlight the transitional nature of spatter between loose pyroclasts and continuous lavas, enhancing the overall buildup of basaltic shields.

Tuff Cones

Tuff cones form through phreatomagmatic eruptions, where rising basaltic encounters or , triggering violent explosions that fragment the magma into fine and . These interactions generate explosive wet eruptions dominated by base surges, producing pyroclastic deposits rather than coherent lava flows. The process begins when magma heats water to , causing rapid expansion and fragmentation, often in shallow subsurface environments. Structurally, tuff cones exhibit wide bases and gentler slopes ranging from 10 to 20 degrees, with typical heights of 50 to 200 meters above the surrounding . This morphology arises from the low-angle deposition of fine-grained during base surge events, resulting in broad, low-relief edifices. Many tuff cones are encircled by surrounding moats formed through of the substrate due to excavation and loading by eruptive deposits. The characteristic deposits of tuff cones consist of cross-bedded tuff rings rich in accretionary lapilli, formed by the aggregation of wet particles in the eruption column. These features indicate the influence of base surges—radial, ground-hugging flows of , , and gas—that can travel distances up to several kilometers (typically 1-5 km) from the vent, depositing layered sequences with undulatory . Such deposits reflect the wet, turbulent nature of phreatomagmatic activity, with pyroclastic layering patterns observed in eruptive materials. Tuff cones predominantly occur in settings with abundant water, such as coastal plains or lacustrine environments, where can readily interact with shallow aquifers or seas. A prominent example is Diamond Head in , a classic coastal cone formed approximately 200,000 to 300,000 years ago through explosive interactions between and -saturated sediments. These landforms are common in volcanic fields with high tables, highlighting the role of hydrological conditions in shaping monogenetic .

Stratocones

Stratocones, also known as composite volcanoes or stratovolcanoes, are polygenetic volcanic edifices built through repeated eruptions over tens to hundreds of thousands of years, resulting in layered deposits of lava flows, pyroclastic materials such as and , and mudflows known as lahars. Unlike the monogenetic cones described elsewhere in this section, stratocones experience multiple eruptive episodes over long periods. These volcanoes exhibit complex buildup processes involving alternating effusive and explosive phases, where viscous lava flows create stable layers interspersed with fragmented ejecta from more violent eruptions, often culminating in the formation of summit craters or calderas. The longevity of stratocones arises from their sustained magmatic activity, with repose periods between eruptions allowing for gradual accumulation and structural reinforcement. Morphologically, stratocones are characterized by their tall, symmetrical to asymmetrical conical profiles, reaching heights of up to 3-4 kilometers above their bases, with steep upper slopes ranging from 30 to 40 degrees and gentler basal slopes of 6 to 10 degrees. This steep-sided form results from the thick, short lava flows and piled pyroclastic deposits that resist , often featuring a central conduit that channels to the surface and may include parasitic vents or lava domes on the flanks. Their broader bases, sometimes spanning several kilometers, provide stability but also make them susceptible to sector collapses and landslides, contributing to their rugged, often snow-capped appearance in temperate regions. The feeding stratocones typically evolves from andesitic to rhyolitic compositions, with silica contents increasing from about 55-65% to 65-75% during ascent, which heightens and gas , promoting more explosive eruptive phases over time. This compositional progression reflects fractional and assimilation within shallow magma chambers at depths of 5-10 kilometers, leading to a spectrum of eruption styles from fluidal flows in early stages to highly destructive Plinian events. Tectonically, stratocones predominate in zone environments, where oceanic plates descend beneath continental margins, generating the hydrous, intermediate magmas that fuel volcanic arcs such as the Pacific .

Rootless Cones

Rootless cones form through explosive interactions between molten lava flows and external water sources, such as wetlands, lakes, or ice, without involvement of fresh from depth. When hot lava, typically basaltic, contacts water-saturated sediments or surface water bodies, rapid vaporizes the water into steam, generating pressure that leads to explosions. These steam-driven blasts excavate underlying material and build small cones from the ejected debris, distinguishing rootless cones as secondary features remote from primary volcanic vents. In appearance, rootless cones are typically small, irregular mounds or clusters, ranging from 1 to 35 meters in and 2 to 450 meters in basal , often grouped in fields of hundreds or thousands. They exhibit rough, scoriaceous surfaces composed of , , and spatter, with shapes that can be circular, elongate, or concentric, lacking the symmetry of magmatic cones. Internally, these structures are filled with fragments of and solidified lava, rather than juvenile , and may show welded spatter caps or inversely from successive explosions. Geologically, rootless cones are prevalent in regions with frequent basaltic eruptions and abundant , such as , where wet climates and glacial influences promote their formation. A prominent example is the Mývatn area in northern , where over 6,500 rootless cones developed approximately 2,000 years ago during the emplacement of the Younger Laxá Lava flow, which interacted with the lake and surrounding wetlands; hosts more than 13,000 such features in total, the highest concentration worldwide. These cones provide insights into paleoenvironmental conditions, indicating former water bodies or saturated grounds beneath ancient lava flows. Diagnostic features of rootless cones include the complete absence of juvenile magmatic material, as explosions recycle pre-existing lava and incorporate local sediments without new ascent. Cross-sections reveal internal structures with layered incorporating lacustrine or sediments, often showing evidence of steam escape conduits or bubble bursts rather than magmatic fragmentation. This contrasts with phreatomagmatic features like tuff cones, which involve active magma-water mixing, but shares explosive steam dynamics in a non-magmatic .

Notable Examples and Distribution

Iconic Volcanic Cones Worldwide

One of the most remarkable examples of a is in , which emerged dramatically on February 20, 1943, in a cornfield owned by local farmer Dionisio Pulido. The eruption began with explosive activity that rapidly built a cone through the accumulation of ejected cinders and bombs, reaching a height of 424 meters by the end of its nine-year duration in 1952. This event, witnessed by residents and scientists alike, destroyed the villages of Parícutin and San Juan Parangaricutiro, burying them under lava flows and ash while covering over 233 square kilometers with . Mount Fuji in exemplifies a classic stratocone, renowned for its near-perfect symmetrical cone shape rising to 3,776 meters above sea level. Formed over the past 100,000 years through alternating layers of lava and pyroclastic material, its last major eruption occurred in 1707 from the Hoei vents on its southeastern flank, producing ashfalls that reached (modern ) and caused widespread agricultural damage. As a dormant and enduring cultural symbol in , , and spirituality, Mount Fuji attracts millions of climbers annually and was designated a in 2013 for its geological and cultural significance. In , represents a complex of spatter and cinder cones formed during Kīlauea Volcano's prolonged East Rift Zone eruption from 1983 to 2018, the longest and most voluminous in the volcano's . The initial high-fountain episodes built the main cone to about 250 meters, followed by sustained lava flows from fissures and vents that produced over 4.4 cubic kilometers of , burying 144 square kilometers of land and extending the island's coastline by 177 hectares through entry. This activity, monitored extensively by the U.S. Geological Survey's Hawaiian Volcano Observatory, highlighted the dynamic interplay of spatter aggregation and cinder buildup in rift-zone settings. Surtsey Island off Iceland's southern coast formed as a cone during a eruption from November 1963 to June 1967, emerging from the ocean floor as a new landmass approximately 1.4 square kilometers in area. The explosive phreatomagmatic activity, driven by seawater interacting with rising magma, constructed the cone through layers of and surge deposits, reaching a maximum height of 174 meters before partial erosion. Designated a in 2008, serves as a unique laboratory for studying primary succession and ecological colonization, with strict access controls preserving its pristine state since inception. The 1783 Laki fissure eruption in produced extensive fields of rootless cones along a 27-kilometer fracture system within the volcanic system. These pseudocraters formed when hot lava interacted with underlying wetlands, generating steam explosions that built small, circular edifices up to 30 meters high amid the outpouring of 15 cubic kilometers of lava—the largest historical effusion on Earth. The eruption's massive release of and other gases into the atmosphere caused severe regional famines in and contributed to , crop failures, and an estimated 6 million human deaths worldwide through climatic perturbations.

Patterns in Occurrence

Volcanic cones exhibit distinct patterns of occurrence tied to major tectonic settings. They are particularly abundant in hotspot provinces, such as the , where basaltic cinder cones frequently form on the flanks of volcanoes due to localized eruptions from the underlying . In zones, like the , monogenetic cones cluster in volcanic fields along the convergent margin where the Nazca Plate subducts beneath the South American Plate, producing andesitic to dacitic compositions influenced by slab-derived fluids. Intraplate rift environments, exemplified by the East African Rift System, host dense alignments of alkali basaltic cones along extensional fractures, reflecting decompression melting in the . Climatic factors significantly modulate cone morphology by altering eruption dynamics through water-magma interactions. In humid or water-rich regions, rootless cones—formed by lava igniting subsurface water or wetlands—and arise from phreatomagmatic explosions, as prominently observed in Iceland's basaltic terrains where over 13,000 such features occur due to frequent lava-water encounters. Conversely, arid basaltic fields favor development, as the scarcity of external water promotes purely magmatic Strombolian eruptions that build piles without hydrovolcanic modification. The spatial density of volcanic cones varies widely but often concentrates in monogenetic volcanic fields. For instance, the in , , encompasses more than 80 monogenetic edifices across a compact 40-km chain, illustrating high-density clustering in intraplate settings. Globally, comprehensive databases document thousands of well-preserved scoria cones from dozens of fields, with broader inventories suggesting tens of thousands of identifiable features when including submarine and eroded examples, though precise counts remain challenging due to preservation biases. Evolutionary trends in cone distribution reveal migration patterns linked to tectonic drift. Along transform boundaries like the in , volcanic fields such as the Clear Lake Volcanic Field demonstrate northward progression of monogenetic activity over millions of years, driven by the relative motion between the Pacific and North American plates that shifts the locus of extension and melting.

References

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  5. https://volcanoes.usgs.gov/vsc/glossary/cinder_cone.html
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  9. https://archive.org/details/lyell-1850-quarterlyjournal-61850geol
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