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Caldera

A caldera is a large, basin-shaped volcanic depression that forms when the ground surface collapses into a partially emptied underlying following a major volcanic eruption. These features are typically circular or elliptical, ranging from 1 to 100 kilometers (0.6 to 62 miles) in diameter, and are much larger than the original volcanic vents they overlie, often rimmed by steep cliffs or scarps. Unlike smaller summit craters or craters, calderas result specifically from volcanic and are associated with explosive eruptions that eject vast volumes of material. Calderas primarily form through the rapid evacuation of from shallow reservoirs during cataclysmic eruptions, causing the overlying rock to fracture and collapse into the void. This process can generate flows, widespread ashfall, and lahars, with eruption volumes often exceeding 1,000 cubic kilometers (240 cubic miles) in supervolcanic events. There are several types of calderas, including explosive collapse calderas from single massive eruptions and resurgent calderas where post-collapse inflation of the floor creates a central dome due to renewed intrusion. Many calderas also fill with to form lakes or experience subsequent lava flows and smaller eruptions, altering their landscapes over time. Notable examples include the in Yellowstone National Park, Wyoming, one of the largest active caldera systems on , formed by a supereruption about 631,000 years ago that expelled over 1,000 cubic kilometers of ash and debris. The in , created 7,700 years ago by the climactic eruption and collapse of , now holds the deeply blue Crater Lake within its 10-kilometer-wide basin. Another prominent site is the in , a resurgent caldera formed 1.25 million years ago at the intersection of major fault systems, spanning about 22 kilometers (14 miles). These calderas highlight the global significance of such features in assessment and geological research, as they remain potential sources of future large-scale eruptions.

Definition and Etymology

Definition

A caldera is a large, basin-shaped volcanic depression greater than 1 kilometer in diameter, formed by the collapse of the ground surface above a partially emptied during or after a major volcanic eruption. This collapse creates a broad, cauldron-like hollow that distinguishes calderas from other volcanic features. Calderas differ from typical volcanic craters, which are smaller depressions usually less than 1 kilometer across and primarily excavated by explosive eruptions rather than structural subsidence. They are also distinct from maars, which are low-relief, broad craters formed by shallow phreatomagmatic explosions where magma interacts with groundwater, resulting in steam-driven blasts without significant magma chamber involvement. Morphologically, calderas exhibit steep, inward-facing walls and a relatively flat , often encompassing multiple vents or fissures from the original eruptive activity. These depressions may accumulate water to form crater lakes or host renewed , such as intracaldera domes or lava flows, in the post-collapse . The geological term "caldera," derived from the word for , was introduced by Christian Leopold von Buch in to describe the Las Cañadas depression on in the [Canary Islands](/page/Canary Islands).

Etymology

The term "caldera" derives from the Spanish word caldera, meaning "" or "cooking pot," a reference to the large, basin-like resembling a , ultimately tracing back to the Latin caldaria for a used to liquids. This linguistic aptly captures the topographic feature's deep, bowl-shaped form. The word entered English-language geological terminology through the work of German geologist Christian Leopold von Buch, who observed the Las Cañadas on during his 1815 visit to the and adopted the local term to describe it. Von Buch formalized its use in his 1825 publication Physikalische Beschreibung der Canarischen Inseln, distinguishing such large volcanic basins from smaller summit craters. In modern volcanology, related terms have emerged to describe specific caldera morphologies, such as "resurgent caldera," which refers to post-collapse uplift driven by renewed magmatic activity, often forming a central dome within the basin. Similarly, "nested caldera" denotes overlapping or concentric collapse structures resulting from multiple eruptive events at the same site. Early usage of "caldera" often led to confusion with volcanic craters, as both were seen as explosive remnants until 20th-century studies clarified the collapse mechanism unique to calderas through detailed field mapping and geophysical analysis.

Formation and Classification

Formation Processes

Calderas primarily form through the evacuation of large volumes of magma from shallow subsurface chambers during high-magnitude volcanic eruptions, resulting in the gravitational collapse of the overlying crustal roof into the evacuated space. This process is driven by the removal of buoyant support provided by the molten magma, causing the surface to subside and create a broad, basin-shaped depression. The primary mechanism involves rapid or sustained magma withdrawal that destabilizes the chamber roof, typically composed of brittle volcanic and sedimentary rocks. Two main models describe the dynamics: piston-like , in which a relatively coherent block of the roof descends uniformly along a near-circular ring fault, and piecemeal , characterized by irregular, fragmented along multiple, inward-dipping faults that produce a more complex . Piston is favored in larger calderas where the geometry supports symmetric loading, while piecemeal styles occur in smaller or structurally heterogeneous systems. withdrawal rates play a critical role, with faster rates promoting coherent piston motion by limiting time for fault propagation, whereas slower rates allow for progressive fracturing and piecemeal fragmentation. These chambers are generally situated at depths of 5-15 km, where pressures and temperatures permit the accumulation and mobilization of viscous, gas-rich . Prior to caldera formation, rhyolitic accumulates incrementally in upper crustal reservoirs within silicic volcanic systems, often over timescales of thousands to hundreds of thousands of years, through repeated injections of basaltic melts that differentiate into silica-rich compositions. This buildup phase creates a thermally mature, crystal-mush-dominated chamber that can reach eruptible conditions under sufficient . Post-formation geophysical surveys, particularly , reveal low-velocity anomalies indicative of residual voids or partially molten remnants in the collapsed chamber, providing evidence of the evacuation scale and structural evolution.

Explosive Calderas

Explosive calderas form through cataclysmic eruptions associated with the Volcanic Explosivity Index (VEI) of 6 or greater (ejecta volumes >10 km³), qualifying as supereruptions at VEI 8 when exceeding 1,000 km³. These events are driven by the rapid evacuation of high-silica magma from shallow chambers, typically 5–10 km deep, leading to the destabilization and collapse of the overlying crust. The eruption dynamics begin with sustained Plinian columns, which can reach heights of 20–50 km and deposit widespread fine ash before transitioning to pyroclastic flows as the column destabilizes due to increasing mass eruption rates. This emptying of the magma chamber generates critical underpressure, triggering subsidence along ring faults. The collapse mechanisms in explosive calderas often manifest as trapdoor or piecemeal styles, where occurs asymmetrically or in blocks rather than as uniform piston-like descent. In collapse, one side of the caldera floor drops preferentially while the opposite margin remains elevated, facilitated by pre-existing structural weaknesses; piecemeal collapse involves fragmented block , allowing progressive chamber evacuation without complete instantaneous failure. These processes are uniquely tied to the violent, ash-dominated nature of the eruptions, contrasting with more gradual in effusive settings. The primary depositional products are extensive sheets, composed of welded and non-welded deposits that blanket areas up to thousands of square kilometers, serving as key stratigraphic markers of the event. Caldera dimensions in these explosive settings scale with the erupted volume, typically ranging from 10 to 100 km in diameter for volumes exceeding 100 km³. Following , many explosive calderas undergo a resurgence , characterized by post-eruption doming of the floor due to isostatic rebound and subsequent recharge into the residual chamber. This recharge, often involving denser magmas intruding lighter silicic remnants, can uplift the caldera floor by several kilometers over timescales of 10⁴ to 10⁶ years, sometimes leading to renewed along ring fractures.

Non-Explosive Calderas

Non-explosive calderas develop primarily on shield volcanoes through the gradual withdrawal of from shallow reservoirs, leading to of the overlying volcanic roof without associated explosive eruptions. This process is driven by prolonged effusive activity, where basaltic drains laterally to feed flank eruptions, causing the to collapse incrementally over periods ranging from years to centuries. Unlike explosive calderas, which form rapidly through evacuations of large volumes of viscous, gas-rich rhyolitic , non-explosive varieties involve low-viscosity basaltic magmas that allow for steady drainage and piston-like or trapdoor-style . The formation often results from repeated episodes of magma or, in some cases, cryptodome intrusions that destabilize the edifice and promote roof failure. Cryptodomes—intrusive bodies of magma that ascend without breaching the surface—can induce zones and faulting at the base of the volcanic pile, weakening the structure and facilitating gradual collapse when combined with ongoing magma withdrawal. rates in these systems are typically slow, on the order of millimeters to centimeters per year during non-eruptive phases, contrasting sharply with the near-instantaneous collapses (meters to kilometers in hours to days) seen in explosive events. This slower pace allows for episodic nesting, where inner caldera walls form terraces or hinges due to multiple subsidence cycles, often partially refilled by subsequent lava flows. A key characteristic is the approximate volume balance between the erupted lava and the subsided caldera floor, with little to no widespread deposits, reflecting the effusive nature of the activity. For instance, during the 2018 eruption, approximately 0.8 km³ of lava erupted from the lower East , directly corresponding to the ~0.8 km³ of summit that enlarged the caldera by up to 500 meters in depth over several months. Classic examples include 's summit caldera, which formed around 1470 CE following the prolonged effusive 'Ailā'au eruption (lasting ~60 years and producing ~5 km³ of lava), and the Mokuaweoweo caldera on , both exhibiting nested morphologies from recurrent flank drainages. Similarly, Sierra Negra in the features a trapdoor-style caldera that has undergone repeated events tied to effusive rim eruptions, with inner walls showing terraced structures from prior collapses. These features highlight the role of sustained supply and drainage in shaping non-explosive calderas over volcanic timescales.

Other Caldera Types

Erosion Calderas

Erosion calderas are large, basin-shaped depressions formed by prolonged differential of ancient volcanic edifices, such as or stratovolcanoes, where softer central materials are removed over millions of years, leaving resistant outer rims. This process exploits structural weaknesses in the volcanic pile, enhanced by fluvial incision, , and , gradually enlarging initial craters or vents into broad, caldera-like hollows. Unlike collapse calderas, erosion calderas develop post-eruption through surficial rather than sudden , often in tropical or temperate climates with high rainfall. These features are identified by the presence of dissected volcanic remnants, such as plugs or dikes forming rims, and infilled with non-volcanic sediments like or , without evidence of recent magmatic activity. They are distinguished from other erosional basins by their association with ancient volcanic and circumferential scarps mimicking collapse margins. In terms of scale, erosion calderas can reach diameters of 10 to 40 km or more, with depths exceeding 1 km, comparable to some explosive calderas. Notable examples include the Tweed Caldera in northeastern , , formed from the of a (active ~23-20 million years ago), spanning about 40 km in diameter and over 1,000 m deep. Another is the Caldera de Taburiente on , , , a caldera approximately 9 km across, carved into basaltic remnants. These examples illustrate how can reshape volcanic landscapes over tens of millions of years, preserving pseudo-caldera morphologies in stable tectonic settings.

Structural Calderas

Structural calderas refer to the architectural styles of collapse in volcanic calderas, defined by the geometry of ring faults and subsidence patterns during magma evacuation. These structures typically involve circumferential normal faults that bound the collapsing block, with variations in shape and symmetry influencing the final morphology. Common types include piston-style subsidence, where the floor drops uniformly as a coherent , and funnel or piecemeal collapse, involving inward-dipping faults and chaotic block rotation. Asymmetric trapdoor collapses occur when subsidence is biased toward one side, often along pre-existing tectonic lineaments. The development is driven by gravitational instability following rapid magma withdrawal, with fault propagation accommodating vertical displacement of 0.5-2 km or more. Ring fracture zones, 1-5 km wide, form steplike scarps around the perimeter, while intra-caldera faults dissect the floor. These structural elements are mapped using geophysical methods like and seismic surveys, revealing negative anomalies over the subsided block and fault traces. In resurgent calderas, post-collapse tectonics can uplift the floor along concentric faults, creating domal structures. Representative examples include the symmetric piston collapse of Caldera (Oregon, USA), ~8 km in diameter with near-uniform subsidence, and the trapdoor-style (New Mexico, USA), ~20 km across with offset along the northeastern margin influenced by regional extension. These structural variations highlight how local interact with volcanic processes to control caldera form and evolution.

Geological and Economic Significance

Mineralization and Resources

Calderas host significant mineral resources primarily through hydrothermal systems that develop in the post-eruption environment, where residual magmatic heat drives fluid circulation within the fractured and permeable caldera floor. This circulation facilitates the precipitation of , typically at shallow depths of less than 1 km, from low-salinity, low- to moderate-temperature fluids (150–300°C). are particularly common in intracaldera settings, where magmatic sources provide the necessary heat and volatiles for mineralizing fluids to ascend through faults and fractures formed during caldera collapse. In addition to epithermal systems, shallow post-caldera intrusions can generate , characterized by disseminated sulfides and stockwork veins associated with intermediate-composition porphyritic rocks. A notable example is the Yanacocha district in , where Au-Cu mineralization occurs alongside high-sulfidation epithermal gold deposits within a volcanic complex linked to caldera-related . These systems form from magmatic-hydrothermal fluids exsolved from crystallizing intrusions, enriching the surrounding rocks in , , and . Mineralization in such caldera environments often peaks between 0.1 and 5 million years after caldera formation, coinciding with phases of resurgence and renewed that recharge the hydrothermal systems. Beyond metallic ores, calderas exhibit substantial potential due to elevated heat flow from cooling chambers, which sustains liquid-dominated or two-phase steam reservoirs at depth. Temperatures commonly exceed 200°C at 1–2 km depth, as observed in systems like , , where geothermal fluids reach up to 330°C in deeper reservoirs. This high supports steam-driven power generation, with caldera-hosted fields contributing significantly to renewable energy output in regions such as the Taupo Volcanic Zone in . Epithermal deposits, many of which form in caldera settings, collectively account for approximately 8% of global production and 17% of silver production, underscoring their economic importance.

Hazards, Monitoring, and Recent Activity

Calderas pose significant volcanic hazards due to their potential for large-scale eruptions, often preceded by periods of unrest characterized by increased and ground deformation. , including swarms, and deformation signals such as uplift or , serve as key to eruptive activity, allowing for potential early warnings. Explosive caldera-forming eruptions with a (VEI) of 7 or higher can eject massive volumes of ash and gas into the , leading to effects lasting years to decades by blocking and disrupting patterns. Modern monitoring of calderas relies on advanced geophysical techniques to detect these unrest signals in . Interferometric Synthetic Aperture Radar (InSAR) and (GPS) networks measure ground deformation, such as uplift rates typically ranging from 1 to 10 cm per year, indicating accumulation beneath the surface. Seismic networks are deployed to record swarms and long-period tremors, providing insights into and changes within the magmatic . These integrated systems enable continuous surveillance, with data often analyzed to forecast potential escalations in activity. Recent unrest episodes at several calderas highlight the ongoing risks as of November 2025. At in , volcanic unrest intensified in 2025 with incremental seismic activity and ground uplift, including burst-like swarms and a notable M4.4 event in 2024 that continued influencing dynamics into the following year. in experienced episodic eruptions within its summit caldera through November 2025, featuring weekly lava fountaining events since December 2024, progressing to episode 36 in early November 2025, with episode 37 forecasted for late November; episode 35 alone produced over 10 million cubic meters of lava. A prolonged seismic swarm at , , starting in late January 2025 and lasting approximately 45 days, showing progressive energy release linked to potential intrusion. Offshore, Axial Seamount off the has exhibited since its 2015 eruption, with geodetic data indicating ongoing accumulation; as of November 2025, an eruption is forecasted for mid-to-late 2026 based on seafloor pressure and temperature trends. Advancements in forecasting include models that predict caldera collapse events by analyzing , , and GPS . A study by McBrearty and Segall developed a trained on Kīlauea's 2018 collapse sequence, achieving accurate time-to-failure predictions using only a fraction of the available for inference. This approach enhances the ability to anticipate sudden structural failures during drain-back eruptions. Mitigation strategies for caldera hazards emphasize preparedness, particularly for supervolcanoes like Yellowstone. Evacuation planning involves coordinated protocols by the Yellowstone Volcano Observatory, including hazard assessments, public outreach, and tailored response plans to minimize impacts from potential eruptions or related events. These efforts focus on timely warnings and infrastructure resilience to protect densely populated or high-traffic areas.

Terrestrial Calderas

Supervolcanoes and Major Examples

Supervolcanoes are volcanic systems capable of producing eruptions classified as magnitude 8 on the (VEI), characterized by ejecting more than 1,000 cubic kilometers of material, typically forming expansive calderas through catastrophic collapse. This threshold, established by the U.S. Geological Survey (USGS), distinguishes them from ordinary large eruptions by their potential for global climatic impacts and vast deposits. While fewer than 20 such events are known in Earth's history over the past 27 million years, they represent extreme examples of explosive caldera formation, often associated with hotspots or zones. The in , , exemplifies a linked to an intraplate , with its most recent supereruption occurring approximately 631,000 years ago during the Lava Creek event, which expelled about 1,000 km³ of rhyolitic material and formed the current 45 x 85 km caldera. This eruption is part of a progression along the track, which has produced three major calderas over 2.1 million years, including the older Huckleberry Ridge (2.08 Ma, ~2,450 km³) and Henrys Fork (1.3 Ma, ~296 km³) calderas to the southwest. Post-caldera resurgence and ongoing geothermal activity underscore its persistent magmatic system. Lake Toba in , , hosts one of the largest known supereruptions, dated to about 74,000 years ago, when approximately 2,800 km³ of dense-rock-equivalent material was ejected, forming a 100 x 30 km caldera now partially filled by . This VEI 8 event produced widespread sheets and ashfall that reached as far as , potentially triggering a with global cooling of 3–5°C for several years. The eruption has been hypothesized to contribute to a genetic bottleneck in human populations, reducing to as few as 1,000–10,000 breeding individuals, though this link remains debated based on genetic and climatic evidence. The in , USA, formed during a major around 1.25 million years ago that produced the Upper Bandelier Tuff, with an estimated volume of about 400 km³. This event, part of the Jemez Volcanic Field, involved evacuation of rhyolitic magma from a shallow chamber, resulting in thick deposits across the region and subsequent doming from renewed . The caldera's resurgence, evident in its central dome rising over 1 km since formation, highlights post-eruptive structural evolution typical of such systems. Long Valley Caldera in , , originated from the Bishop Tuff eruption approximately 760,000 years ago, which released over 600 km³ of rhyolitic material and collapsed a 32 x 16 km structure along the Walker Lane shear zone. This VEI 7 event, while not reaching scale, qualifies as a major caldera-forming explosion with flows covering more than 2,200 km² and ash extending across the continent. The caldera remains seismically active, with ongoing swarms and deformation linked to a mid-crustal body, monitored closely by the USGS for potential unrest.

Regional Examples

In , notable calderas include in , formed approximately 7.7 thousand years ago (ka) by the climactic eruption of , which ejected about 50 cubic kilometers of and led to the collapse of the volcanic edifice. The summit caldera of volcano in represents an ongoing example of a shield caldera, characterized by frequent effusive eruptions within a broad, low-relief structure typical of Hawaiian volcanism. Europe hosts several significant calderas, such as Campi Flegrei (also known as the ) near , , which features a nested structure resulting from multiple collapse events, including the around 39 ka and the Neapolitan Yellow Tuff around 15 ka. In the , the () formed during the circa 1600 BCE, a Plinian event that expelled over 30 cubic kilometers of dense-rock equivalent magma and profoundly impacted regional civilizations. In and , the in southern is a 20-by-17-kilometer structure that encompasses the post-caldera , which has produced frequent explosive and effusive activity since about 13 ka. The in exemplifies an erosion-volcanic hybrid, where the 22-kilometer-wide structure formed from the collapse of a about 2.5 million years ago, followed by extensive and mass-wasting that has deepened and modified the volcanic basin over time. South America and Oceania feature active calderas like the Taupō caldera in New Zealand's North Island, which originated from the Oruanui supereruption approximately 25.5 ka, discharging around 530 cubic kilometers of predominantly rhyolitic magma and shaping the modern lake-filled depression. In , the Laguna del Maule volcanic field includes a resurgent caldera exhibiting unrest, with accelerated uplift exceeding 20 centimeters per year since 2013 and rates up to 29 cm/year as of 2020; increased seismicity prompted a alert in August 2025. Globally, caldera distributions show a strong concentration along the , the tectonically active circum-Pacific belt encompassing zones and hotspots that host about 75 percent of Earth's active volcanoes, including many caldera-forming systems. Approximately 20 caldera systems worldwide remain potentially active, with ongoing monitoring focused on those in volcanic arcs like the and .

Extraterrestrial Calderas

On the Moon

Lunar calderas are exceptionally rare compared to those on , with most identified features being small pit craters associated with basaltic rather than large structures. These pit craters, often resembling the summit depressions of volcanoes, form through mechanisms like roof over drained lava tubes or localized during effusive eruptions. The Moon's lower and lack of atmosphere contribute to their smaller , limiting magma reservoir development and favoring dispersed, low-viscosity flows over centralized edifices. In the Marius Hills region of , a prominent volcanic complex, pit craters exemplify these shield-like caldera analogs, with diameters typically around 1 km. This area hosts the highest concentration of lunar volcanic landforms, including over 360 cones and domes formed from viscous lavas during mare emplacement. High-resolution images from the (LRO) reveal floor fracturing in these pits, indicative of structural instability, while nearby sinuous rilles—meandering channels up to several kilometers long—suggest drainage of molten lava that contributed to collapse. These features date to 3–4 billion years ago (Ga), aligning with the peak of lunar mare volcanism in the period. The Orientale Basin, a well-preserved multi-ring approximately 930 km in diameter, exhibits possible volcanic collapse features amid its inner rings, where mare basalt infilling interacted with basin topography. LRO data highlight floor fracturing and subdued craters, such as the 42-km-wide Kopff crater, previously interpreted as a volcanic caldera but now recognized as an impact modified by subsequent lava flooding around 3.36 Ga. Sinuous rilles within the basin, imaged by LRO's Narrow Angle Camera, imply lava drainage paths that may have influenced localized subsidence, tying these elements to the broader 3–4 Ga volcanic episode. Overall, lunar caldera-like structures range from 0.5 to 10 km in diameter, significantly smaller than terrestrial counterparts due to the Moon's reduced , which promotes rapid magma ascent via dikes rather than shallow accumulation.

On Mars

Martian calderas are primarily associated with massive shield volcanoes in the region, formed through prolonged effusive eruptions of basaltic lava with minimal explosive activity, resulting in broad, low-relief structures unlike the more explosive calderas on . These features are evident in the , a chain of three aligned giants—Ascraeus Mons, , and —each capped by summit pits and nested caldera complexes that developed during shield-building phases dominated by fluid lava flows rather than violent blasts. The thin Martian crust, lacking active , permitted these edifices to grow to enormous scales by allowing to accumulate without frequent disruption, making them the largest volcanic structures in the solar system. The most prominent example is , whose summit hosts a nested caldera complex measuring 60 km by 80 km, consisting of six overlapping collapse pits formed by successive drainings of shallow chambers during late-stage activity. Volcanic activity at Olympus Mons spanned from the period to as recently as less than 10 million years ago, with the youngest lava flows and caldera collapses indicating prolonged basaltic effusions that built its 25-km-high shield over billions of years. High-resolution images from the instrument on NASA's reveal fault scarps and stepped margins along the caldera walls, suggesting ongoing structural adjustments tied to past . The exhibit similar summit pits, with featuring a 110–115 km wide caldera rich in terraced walls and radial fractures from effusive shield construction, while Pavonis and Ascraeus Mons show elongated collapse features aligned with regional rifts. Thermal Emission Imaging System () data from Mars indicate anomalously warm surfaces and flow-like features within these calderas, hinting at relatively recent volcanism, potentially within the last 100–150 million years, when low-viscosity basaltic lavas resurfaced the interiors. Alba Mons, another Tharsis outlier, extends up to 600 km across at its base with a summit caldera around 100 km in diameter, its vast width enabled by the same crustal conditions that fostered the region's giants.

On Venus and Io

Calderas on Venus, identified primarily through radar imaging by NASA's Magellan spacecraft, are associated with large shield volcanoes and exhibit diverse morphologies, including summit collapse pits and sag structures. These features are larger than typical terrestrial shield calderas, with diameters often exceeding 20 km, suggesting deeper or more voluminous magma chambers. Many Venusian calderas appear partially or completely filled with subsequent lava flows, indicating post-collapse volcanic activity. Notable examples include Sacajawea Patera, an elongated caldera measuring 120 by 215 km in diameter and 1-2 km deep, characterized by and fault scarps along its margins. Sachs Patera, a sag caldera, forms an elliptical depression 130 m deep, surrounded by radar-bright lava flows that suggest relatively recent emplacement. Calderas are more prevalent on than initially thought, often linked to shield volcanoes, and contribute to the planet's extensive volcanic landscape, which covers about 90% of its basaltic surface. Evidence of recent activity includes fresh radar properties and low infrared emissivity at sites like Idunn Mons, where summit calderas host young lava flows estimated at 250,000 to 2.5 million years old, potentially as recent as a few years based on mineralogical models. As of 2025, assessments confirm is likely volcanically active today, with the strongest evidence at Idunn Mons. Such features imply ongoing volcano-tectonic processes on , contrasting with its stagnant lid tectonic regime. On , Jupiter's innermost , calderas are abundant and integral to its extreme , driven by intense from gravitational interactions with and neighboring . The hosts over 420 identified calderas, far outnumbering those on , with about 15 active vents at any time; these structures are significantly larger, often spanning tens to hundreds of kilometers, and lack impact craters due to constant resurfacing. Prominent calderas include Tvashtar Catena, a chain of giant collapse pits at 60°N, 120°W, site of energetic eruptions observed by Galileo spacecraft in 2000, producing plumes and extensive sulfurous flows. Heno Patera, another large caldera, generated flows covering 120 square miles during a 2014 outburst detected by ground-based telescopes. Chaac Patera features nested calderas with bright sulfur deposits, while Prometheus caldera exhibits episodic venting of gases and lavas. Recent observations from the James Webb Space Telescope (JWST) in November 2025 reveal active volcanism, including new infrared hotspots and a resurfaced Loki Patera, the largest lava lake. Additionally, NASA's Juno mission discovered a powerful volcanic hotspot in Io's southern hemisphere in January 2025. Volcanic activity has persisted for billions of years, with caldera floors reaching temperatures of 350-1800 K and comprising up to 2% of Io's surface area.