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Caves in Volcanic Terrains in Costa Rica with the Description of New Volcano-Speleogenetic Mechanisms
Abstract
The continental territory in Costa Rica is composed in 50% of Cretaceous to Quaternary volcanic rocks. However, volcanic caves sensu strictu (formed only by volcanic processes) are very rare due to the geotectonic conditions of the Pre-Oligocene submarine volcanism, and rheological conditions of Neogene-Quaternary subalkaline lava flow in a subduction zone. A total of 90 volcanic caves are reported in the country, with a total length of passages of ~ 2.2 km. A few reported lava tubes (pyroducts) are related to Middle-Upper Pleistocene basaltic to basaltic-andesitic aa lava flows. However, there are an enormous number and variability of caves of different origin and hosted in volcanic terrains like mold caves in lahars, piping caves, erosion caves in fluvial settings (lateral erosion of a river or at the base of a waterfall) and littoral systems, including those in which the cave formed along fault zones or a stratigraphic contact in ignimbrites. Less common are dissolution caves in active hydrothermal systems, or caves in ignimbrites probably formed in a similar way as tumuli or pressure ridges in lava flows. Caves can form in fluvial systems when erosion happens at a stratigraphic contact within an ignimbrite package or when large blocks fall, and landslides occur in a narrow valley followed by further erosion at the base. Sometimes, the rock above the cave can be used as a natural bridge when the length is short. Several caves are the result of complex processes or are of mixed origin. A few other caves were apparently enlarged by anthropogenic interventions (or possibly by Plio-Pleistocene megamammals). More studies are required in order to better understand the diversity of the given volcano-speleogenetic processes.
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The network of lava tubes is one of the most unexploited natural wonders of the Galapagos Islands. Here, we provide the first morphological, mineralogical, and biogeochemical assessment of speleothems from volcanic caves of the Galapagos to understand their structure, composition, and origin, as well as to identify organic molecules preserved in speleothems. Mineralogical analyses revealed that moonmilk and coralloid speleothems from Bellavista and Royal Palm Caves were composed of calcite, opal-A and minor amounts of clay minerals. Extracellular polymeric substances, fossilized bacteria, silica microspheres and cell imprints on siliceous minerals evidenced microbe-mineral interactions and biologically-mediated silica precipitation. Alternating depositional layers between siliceous and carbonate minerals and the detection of biomarkers of surface vegetation and anthropogenic stressors indicated environmental and anthropogenic changes (agriculture, human waste, cave visits) on these unique underground resources. Stable isotope analysis and Py-GC/MS were key to robustly identify biomarkers, allowing for implementation of future protection policies.
This study presents the first hydrogeochemical model of the hydrothermal systems of Turrialba and Irazú volcanoes in central Costa Rica, manifested as thermal springs, summit crater lakes, and fumarolic degassing at both volcanoes. Our period of observations (2007–2012) coincides with the pre- and early syn-phreatic eruption stages of Turrialba volcano that resumed volcanic unrest since 2004, after almost 140 years of quiescence. Peculiarly, the generally stable Irazú crater lake dropped its level during this reawakening of Turrialba. The isotopic composition of all the discharged fluids reveals their Caribbean meteoric origin. Four groups of thermal springs drain the northern flanks of Turrialba and Irazú volcanoes into two main rivers. Río Sucio (i.e. “dirty river”) is a major rock remover on the North flank of Irazú, mainly fed by the San Cayetano spring group. Instead, one group of thermal springs discharges towards the south of Irazú. All thermal spring waters are of SO 4 -type (i.e. steam-heated waters), none of the springs has, however, a common hydrothermal end-member. A water mass budget for thermal springs results in an estimated total output flux of 187 ± 37 L/s, with 100 ± 20 L/s accounted for by the San Cayetano springs. Thermal energy release is estimated at 110 ± 22 MW (83.9 ± 16.8 MW by San Cayetano), whereas the total rock mass removal rate by chemical leaching is ~ 3000 m ³ /year (~ 2400 m ³ /year by San Cayetano-Río Sucio). Despite Irazú being the currently less active volcano, it is a highly efficient rock remover, which, on the long term can have effects on the stability of the volcanic edifice with potentially hazardous consequences (e.g. flank collapse, landslides, phreatic eruptions). Moreover, the vapor output flux from the Turrialba fumaroles after the onset of phreatic eruptions on 5 January 2010 showed an increase of at least ~ 260 L/s above pre-eruptive background fumarolic vapor fluxes. This extra vapor loss implies that the drying of the summit hydrothermal system of Turrialba could tap deeper than previously thought, and could explain the coincidental disappearance of Irazú’s crater lake in April 2010.
There has been little research on the genesis and development of pyroducts (or lava tubes) originating from Gala´pagos volcanoes. Pyroducts are responsible for the lateral, post-eruptive transport of lava because they are highly effective as thermal insulators. After eruptions terminate, these conduits often become accessible as caves. In March 2014 the 16th International Symposium on Vulcanospeleology brought a large group of vulcanospeleological specialists to the Islands. During the meeting a number of pyroducts were visited and studied in context on the island of Santa Cruz and around Isabella’s Sierra Negra volcano in the western, most active, part of the Gala´pagos. The longest of the caves, Cueva del Cascajo, about 3 km in length, was partly surveyed and nine other caves were visited. Structural features such as thickness of roof, evidence of downcutting, presence of oxbows, secondary ceilings, lavafalls, collapses and pukas were particularly studied for evidence they reveal about developmental stages of pyroducts. The resulting data show that the pyroducts were formed by "inflation" with the primary roof consisting of uninterrupted paŻhoehoe sheets. No pyroducts were identified that developed by the crusting-over of channels. The studies strongly confirm inferences drawn from other hot-spot related islands, such as Hawai’i.
Natural caves that emit geogenic CO2 appear to be very rare; here we report CO2 measurements from Cueva de la Muerte, Costa Rica, a natural cave developed in recent volcanic rocks. The CO2 is strongly
stratified, emerging from the cave in a density flow that hugs the ground. The total CO export from the
Cueva de la Muerte is significant, estimated at approximately 272 ± 5.6 metric tonnes of CO2 per year. We propose a new term to distinguish such caves from caves with non-geogenic CO2: “mofette cave”.
Keywords: Geogenic-CO2, hypogene, geothermal.
This paper presents the data derived from the geological mapping of the Paraíso sheet (3445-IV23), 1:10.000 scale, located within the Central Valley of Costa Rica, together with the most relevant structural and hydrogeological aspects. In general, the existence of a rocky basement associated with the Pacacua Formation of the Upper Miocene, discordantly overlain by materials from the Irazú paleovolcano, related to the Paraíso Formation of the Middle Pleistocene and to the Reventado Formation of the Upper Pleistocene was determined. Due to the climatic conditions and to the composition of the volcanic materials the unit El Rincón Laterite Bed has been developed, which appears in the greater part of the sheet. The above materials are overlaid discordantly by the Upper Pleistocene Alluvial Deposits and by the Lacustrine Deposits, whereas the Current Alluvial Deposits overlap discordantly to the previous materials due to changes in the base level of the rivers produced by the active tectonics in the region. According to morphological observations, a structural model with an axis of N-S orientation stresses, consisting of E-W orientation inverse faults, with shear faults associated with NE-SW and NW-SE orientation is proposed. The hydrogeological model is formed by two aquifers associated with lava flows, with intermediate capacity and affected by the effects of tectonic activity in the sector E of the quadrangle.
The caves of the Irazú volcano (Costa Rica), became accessible after the partial collapse of the NW sector of the Irazú volcano in 1994, offering the opportunity to investigate active minerogenetic processes in volcanic cave environments. We performed a detailed mineralogical and geochemical study of speleothems in the caves Cueva los Minerales and Cueva Los Mucolitos, both located in the northwest foothills of the main crater. Mineralogical analyses included X-ray diffraction (XRD) and Raman spectroscopy, while geochemical characterization used Energy Dispersive X-ray spectroscopy (EDX) coupled to Scanning Electron Microscopy (SEM). In addition, measurements of environmental parameters in the caves, cave drip water and compilation of geochemical analyses of the Irazú volcanic lake (~150 m above the cave level) and fumarole analyses were conducted between 1991 and 2014. We identified forty-eight different mineral phases, mostly rare hydrated sulfates of the alunite, halotrichite, copiapite, kieserite and rozenite groups, thirteen of which are described here as cave minerals for the first time. This includes the first occurrence in cave environments of aplowite, bieberite, boyleite, dietrichite, ferricopiapite, ferrinatrite, lausenite, lishizhenite, magnesiocopiapite, marinellite, pentahydrite, szomolnokite, and wupatkiite. The presence of other new cave minerals such as tolbachite, mercallite, rhomboclase, cyanochroite, and retgersite, is likely but could not be confirmed by various mineralogical techniques. Uplifting of sulfurous gases, water seepage from the Irazú volcanic lake and hydrothermal interactions with the volcanic host rock are responsible for such extreme mineralogical diversity. These findings make the caves of the Irazú volcano a world-type- reference locality for investigations on the formation and assemblage of sulfate minerals and the biogeochemical cycle of sulfur, with potential implications for Astrobiology and Planetary science.
Monte de la Cruz complex piroclastic cone is located on the southeast footslope of Barva Volcano. This cone produced the Ángeles lava flow (7,3 km, área 12,8 km2). Through geomorphological, petrographical and field studies, two units were recognized: Lower and Upper Ángeles. Petrographically, the Lower Ángeles corresponds with a vesicular andesitic-basaltic lava, with a hypocristalline porphyritic to glomeroporphyritic texture, with phenocrystals of plagioclase, clinopyroxene, orthopiroxene, olivine and opaque crystals. On the other hand, the Upper Ángeles is a vesicular andesitic lava with hypocristalline, glomeroporphyritic to glomeroporphyritic seriate texture, with phenocrystals of plagioclase, clinopyroxene, orthopiroxene, olivine and opaque crystals. Morphologically kipukas and lévees were observed. Regionally the Monte de la Cruz cone along with other minor satellite cones are aligned N19°W over 8,5 km, yielding a possible origin associated with a volcano-tectonic fracture.
El Puente de Piedra es una estructura ubicada en el flanco suroeste del volcán Poás, fue formada por procesos de erosión diferencial en rocas volcánicas (depósitos ignimbríticos) que han estado activos por miles de años, en el río Poró. Su importancia radica en que fue declarado patrimonio natural de Costa Rica el 21 de abril de 1994, bajo el decreto número 23 1111- 06, y que por sus características como: edad (Pleistoceno Medio) tamaño y funcionalidad, es uno de los pocos que hay en el mundo. Por estas razones es que su preservación es muy importante para asegurar el disfrute por las próximas generaciones. Se presenta una caracterización geológica y geomorfológica no solo el puente, si no la región en la que está ubicado, además de la evaluación de su estado actual con un inventario de daños y problemas que lo afectan. Se identifica el uso de la tierra en su entorno y como el cambio en ellas lo impactaría negativamente en el futuro. Para realizar la descripción geomorfológica detallada del puente se realizó un levantamiento lídar de la estructura y se generó un modelo 3D de la estructura, del cual se obtuvieron sus datos paramétricos y que también se utilizará como memoria histórica de la estructura. Los resultados obtenidos de este trabajo pueden ser el punto de partida para definir un programa de intervención, conservación y mantenimiento de la estructura, así como un incentivo para que la comunidad de Grecia pueda generar y disfrutar de un mayor aprovechamiento turístico de este sitio. Actualmente la oferta turística de sitios con atractivo geológico alrededor del volcán Poás funcionan de forma desligada y no hay interconexiones en cuanto a los aspectos geológicos, biológicos y culturales. Ligando estos campos se podría ayudar a fomentar el desarrollo de las comunidades cercanas al volcán y se podrían dar los primeros pasos hacia un concepto de geoparque.
The Frasassi caves present a unique opportunity to study sulfuric acid speleogenesis in a large karst system that contains active sulfidic processes as well as relict features produced by past speleogenetic episodes. The caves consist of a network of ramifying, mainly subhorizontal passages that reach more than 30 km in total length, and are organized in superimposed and interconnected levels. Sulfidic groundwaters are accessible in the lowermost levels. The water chemistry in the shallow phreatic zone is influenced by mixing phenomena between the sulfidic groundwaters and descending oxygenated water and, to some extent, gas exchange with the cave atmosphere. The sulfidic waters are corrosive with respect to limestone, with average limestone dissolution rates around 100 mm 10⁻³ year⁻¹ for submerged tablets. The release of gases to the air also causes wall corrosion (linear corrosion rate up to 85 mm 10⁻³ year⁻¹), which produces gypsum replacement crusts above the water table. Morphological and isotopic analyses show that large relict gypsum deposits in the upper dry levels were created by the same mechanism. Sulfide-oxidizing chemosynthetic bacteria living in the cave produce organic matter and support a rich and diverse ecosystem in the sulfidic branches, and these microorganisms contribute to sulfur cycling and cave formation processes. The evolution of the older cave levels during the Pleistocene was a complex result of changing regional geomorphological and hydrogeological regimes as well as local factors that affect water movement and gas exchange in the shallow phreatic zone within the cave.
In the last ten years, more than 1,500 large burrows have been discovered in southern and southeastern Brazil, dug in rocks that include weathered granitic and basaltic rocks, sandstones, and other consolidated sediments. Their presence in geological units of Plio-Pleistocene age suggests that large extinct mammals produced these structures. The internal walls exhibit scratches and grooves left by the animals that inhabited these structures. The burrows are straight or slightly sinuous tunnels that measure up to tens of meters in length. One smaller type measures up to 1.5 meter in diameter, and the larger type can reach 2 meters in height and 4 meters in width, suggesting that such structures have been produced by at least two kinds of organisms. This contribution proposes a classification for these ichnofossils under the generic designation Megaichnus igen. nov., consisting of two ichnospecies identified so far: M. major and M. minor ispp. nov. Although the exact identity of the producers of the burrows is yet unknown, the dimensions and morphology point to ground sloths and giant armadillos.
Tree mould caves originated by several geological/geomorphological processes in various solid rocks are remarkable natural phenomena. But existing knowledge about these caves is not precise and is inconsistent with the basic principles of cave genetic classification, related to geomorphological processes of origin and enlargement of underground hollows. On the basis of field observations of tree mould caves formed in volcanic and volcaniclastic rocks (Japan, Central Europe) and travertine (Central Europe), a genetic classification of tree mould caves (syngenetic–pyrogenic, epigenetic mechanical weathering and biogenic destructive types) is proposed and discussed.
Cueva de Villa Luz (a.k.a. Cueva de las Sardinas) in Tabasco, Mexico, is a stream cave with over a dozen H2S-rich springs rising from the floor. Oxidation of the H2S in the stream results in a abundant, suspended elemental sulfur in the stream, which is white and nearly opaque. Hydrogen sulfide concentrations in the cave atmosphere fluctuate rapidly and often exceed U.S. government tolerance levels. Pulses of elevated carbon monoxide and depleted oxygen levels also occassionally enter the cave. Active speleogenesis occurs in this cave, which is forming in a small block of Lower Cretaceous limestone adjacent to a fault. Atmospheric hydrogen sulfide combines with oxygen and water to form sulfuric acid, probably through both biotic and abiotic reactions. The sulfuric acid dissolves the limestone bedrock and forms gypsum, which is readily removed by active stream flow. In addition, carbon dioxide from the reaction as well as the spring water and cave atmosphere combines with water. The resultant carbonic acid also dissolves the limestone bedrock. A robust and diverse ecosystem thrives within the cave. Abundant, chemoautotrophic microbial colonies are ubiquitous and apparently act as the primary producers to the cave's ecosystem. Microbial veils resembling soda straw stalactites, draperies, and 'u-loops' suspended from the ceiling and walls of the cave produce drops of sulfuric acid with pH values of <0.5-3.0 ±0.1. Copious macroscopic invertebrates, particularly midges and spiders, eat the microbes or the organisms that graze on the microbes. A remarkably dense population of fish, Poecilia mexicana, fill most of the stream. The fish mostly eat bacteria and midges. Participants in an ancient, indigenous Zoque ceremony annually harvest the fish in the spring to provide food during the dry season.
A regional survey of the caves of the state of Rio Grande do Sul, Brazil, listed hundreds of caves with varied origins. Among these, we identified two large caves with special characteristics, one located in the city of Santa Cruz do Sul and the other in the municipality of Vale Real. Both evolve in an approximately horizontal plane, extend tens of meters into the interior of the respective elevations, and do not show any signs of present or past underground drainage. Concave surfaces on the walls stand out in their morphologies, which suggest that the caves originally constituted a system of ellipsoidal chambers, each chamber with original height of approximately 1.5 m and diameter between 3.5 and 7 m. The individual chambers were connected by relatively short tunnels. These chambers are best preserved in the cave of Santa Cruz do Sul; the cave of Vale Real appears to have been much disfigured, both because of inorganic processes and anthropogenic action. The general characteristics of these two caves enable us to propose that they originated from the activity of digging ground sloths of the South American Megafauna. Their dimensions suggest that they were excavated and inhabited not by individual animals, but by groups of sloths. The original polished walls suggest that the caves were used for extended periods, possibly in the order of centuries. Their morphology is so different from other tunnel systems that were excavated by the Megafauna and found in southern Brazil, that we suggest that this morphology of chamber systems is associated with a specific species of ground sloth, whose identification will be very difficult.
ABSTRACT: The natural and selective erosion of the volcanic rocks that compound it has formed Puente de
Piedra (Rock Bridge). This is a nice example on the manifestation of the erosion processes in Nature. This natural
structure might be considered as a natural arch or as a natural bridge. Its base shows evidences of strength
increment due to compression. Taxonomically, Puente de Piedra is a Meandering Natural Bridge if all its attributes
are considered.
Keywords: Rock bridge, Costa Rica, natural arch, meandering natural bridge.
RESUMEN: El Puente de Piedra se ha formado por la remoción natural y selectiva de las rocas volcánicas que
lo forman, es decir, es el resultado de la manifestación de procesos erosivos. Esta estructura natural puede considerarse
como un arco natural o como un puente natural. Su base presenta el efecto de incremento de resistencia
por compresión. El Puente de Piedra se ha clasificado, taxonómicamente, como un Puente Natural
Meándrico de acuerdo con sus atributos
A new population of velvet worms (Onychophora) inhabiting a lava tube cave in the island of Santa Cruz, Galapagos, is reported here. The population size is large, suggesting that they may be troglophilic. Its members are darkly pigmented, with no obvious troglomorphic features. Their 16S rRNA sequence showed no differences when compared to an unidentified species of surface velvet worm from the same island, thus supporting cave and surface populations belong to the same species. Based on the 16S rRNA data, the Galapagos velvet worms derived from an Ecuadorian/Colombian clade, as would be expected of ease of dispersal from the nearest mainland to the Galapagos Islands.
Snottites are extremely acidic (pH 0–2) biofilms that form on the walls and ceilings of hydrogen sulfide-rich caves. Recent work suggests that microbial communities including snottites and related cave wall biofilms accelerate cave formation by oxidizing sulfide to sulfuric acid. Therefore, we used full-cycle rRNA methods and metagenomics to explore the community composition and sulfur metabolism of snottites from the sulfidic Frasassi and Acquasanta cave systems, Italy. Acquasanta snottites were dominated by strains of Acidithiobacillus thiooxidans, with a smaller population of Ferroplasma sp. Frasassi snottites were also dominated by At. thiooxidans but with a more diverse community including relatives of ‘G-plasma’ (Thermoplasmatales), Acidimicrobium, and rare taxa. We identified diverse homologues of sulfide:quinone oxidoreductase (SQR) in the metagenomic datasets. Based on phylogenetic analysis, the numerically dominant At. thiooxidans populations have four different types of SQR, while Ferroplasma has two and Acidimicrobium and G-plasma each have one. No other genetic evidence for sulfur oxidation was detected for either Acidimicrobium or G-plasma, suggesting that they do not generate sulfuric acid. Our results confirm earlier findings that At. thiooxidans is the dominant primary producer and sulfide oxidizer in sulfidic cave snottites.
La colada de Cervantes se ubica en el flanco sureste del volcán Irazú, en Costa Rica, y es el flujo de lava más reciente y grande datado en este volcán. Este campo está constituido por dos flujos de lava que presentan una composición diferente. El flujo occidental (10,85 km², 0.18 ± 0.1 km³) es de composición basáltica (SiO : 50,71-52,06%, MgO: 8,13-9,50%) y basáltica andesítica debido a mezcla de magma (SiO : 52,90-53,42%, MgO: 6,71-7,12%), y es más viejo (57 ka ± 13 ka años a.P.). El flujo oriental (28,14 km², 1,14 ± 0,25 km³) es de composición basáltica andesita (SiO : 55,54-56.58%, MgO: 4,4-5,26%) y es más joven (~16 840 años a.P.). La colada de Cervantes muestra distintas morfologías superficiales tales como canales, levées y topografía tipo hummocky. La estructura interna de la colada está compuesta por varias unidades de lava masiva e intercalaciones de auto brechas (con presencia de bolas de lava). El flujo Occidental está compuesto por flujos de lava de tipo escoriácea y flujos en bloques, los cuales a su vez están cubiertos de ceniza, y con un espesor inferior a 20 m, con excepción del río Reventazón, en donde posee un espesor de aproximadamente 150 m, creando a su vez el paleo-lago Cachí. Sin embargo, el flujo Occidental presenta una composición más básica (posiblemente mayor fluidez), pequeñas dimensiones, tanto en espesor como extensión, resultado de bajas tasas de efusión, pendientes altas, y/o el cese de efusión de lava. El flujo Oriental fue originado a partir de fisuras ubicadas en sitios de baja altitud, y su espesor y extensión, además de la presencia de levées, son características que permiten relacionarlo con periodos de mayor efusión o descarga. Únicamente el flujo Oriental tiene zonas de no depositación de lava (kipukas) y una serie de depresiones de diferentes dimensiones y un patrón sinuoso, resultado de un antiguo valle fluvial cubierto por la lava. En el flanco sur del Irazú presenta un par tectónico conjugado (N34ºE and N26ºW, σ1 orientado N04°E) conformado por una serie de fisuras, cráteres y conos, con una longitud de 2 km, estructuras que constituyen la fuente de emisión de la colada de Cervantes. Dichos sectores podrían eventualmente presentar en el futuro actividad eruptiva.
La Isla del Coco es la única isla oceánica y el único afloramiento subaéreo de la Cordillera Volcánica del Coco, el rasgo geográfico y geológico más extenso en aguas territoriales costarricenses. Desde el punto de vista geológico, está conformada por rocas volcánicas, predominantemente coladas de lavas basálticas y traquíticas en menor cantidad, con rocas piroclásticas y epiclásticas subordinadas. Posee suelos, coluvios y depósitos de playas (arenas y cantos) superficiales; su topografía es muy variable pero predomina el relieve quebrado y rugoso. La Isla del Coco es la parte emergida de un volcán submarino de evolución compleja, desarrollado a partir y durante el Pleistoceno Inferior (entre 2.2 y 1.5 millones de años, Ma), producto de una anomalía térmica en el manto a través de varias fisuras, que originaron varios alineamientos de volcanes submarinos. La Isla del Coco se encuentra en un estadio de erosión activo, y sus arcos y plataformas sumergidas (90-110m y 183m) son probablemente el producto de una erosión subaérea durante las dos últimas máximas glaciaciones, combinados quizás con la subsidencia debida al enfriamiento del escudo volcánico y de la corteza oceánica. Al ser la isla geológicamente joven, posee importantes implicaciones para la comprensión de la evolución y el endemismo de su biodiversidad. Las amenazas en la geodinámica principales identificadas son los deslizamientos, los tsunamis y, en menor grado, la sismicidad, poco frecuente y con magnitudes moderadas (≤ 5.8 Mw hasta la fecha) dentro de un radio de alrededor de 300km, predominantemente asociada con fallas dextrales de rumbo N-S. Los pocos datos obtenidos hasta el momento indican que hay un cierto grado de actividad sísmica en los alrededores de la Isla del Coco, relacionados con las fallas locales. Algunos pequeños tsunamis históricos y prehistóricos han afectado a la Isla del Coco y los sismos así como la precipitación pluvial elevada han generado deslizamientos. La licuefacción está restringida a las dos playas arenosas (bahías Chatham y Wafer).
In 2005, the residents and the neighborhoods of Zone 6 and Zone 2 in Guatemala City began to complain to the authorities about the rumbling and shaking in their homes. Guatemala is located in a seismic zone and has volcanic activity; these complaints were not taken seriously until February 22, 2007 when the first sinkhole collapse occurred in Zone 6. Many geologists, soils engineers, civil engineers, sanitary engineers, reporters, journalists and politicians theorized about the causes of this collapse. Investigations from professional organizations and professionals from various institutions gave different opinions without determining a cause or giving solutions for the collapse. One of the proposals called for filling the sinkhole immediately. Congress approved the budget to do the work and the work was completed. Unfortunately, by May 29, 2010, a second sinkhole collapse occurred in Zone 2 with terrible consequences, including a three-story building falling into it and the disappearance of at least three people. After this second phenomenon, information about the sewer system of the city was released by professionals involved in the design in the late 1970s. The sewer system was supposed to be extended but, due to costly financial burdens and change of authorities, the project was never finished as it was designed. Many of the manholes of the system were sealed with streets paved and/or filled for new urban developments. It is of high priority to thoroughly analyze the impact of the outdated sewer system on the current population to prevent the occurrence of another sinkhole.
Durante la noche del 8 de diciembre de 1994, en un área inestable del flanco norte del volcán Irazú, ocurrió una avalancha de escombros volcánicos con lahares asociados, así como la caída de “ceniza” que alcanzó hasta unos 30 km al suroeste del volcán. En ese entonces, los procesos, fueron interpretados como el resultado de una explosión freática. Sin embargo, la revisión de las descripciones expuestas en los informes científicos y otros documentos de la época, en conjunto con el análisis de la geomorfología obtenida a partir de fotografías aéreas tomadas el 20 de diciembre de 1994, por el Instituto Geográfico Nacional, nos conduce a discutir sobre la validez de esa interpretación, que aunque no se descarta, parece improbable. En este trabajo se propone que los hechos e información disponible nos acercan más a la hipótesis de la ocurrencia de la avalancha de escombros volcánicos producto de un deslizamiento de un segmento septentrional importante cercano a la cúspide y, en consecuencia, la ¨ceniza¨ podría ser interpretada como el polvo producto de la auto-fragmentación de los bloques rocosos de la avalancha.
Both primary and secondary caves occur in volcanic rocks. Secondary caves are either tectonic (fissure caves) or erosional (sea caves; erosional river caves). Primary caves include: tree and animal casts, hollow tumuli, drained lava tongues, pressure ridge caves, or empty vents, hundreds meter deep. The longest caves form by lateral subterraneous lava transport, termed “pyroducts” (Coan, 1844) (alias lava “tunnels” or “tubes”), integral features of pāhoehoe lava flows. They form by “inflation” at the active, downslope tip of flows or by crusting-over of channels. Internal lava falls cause their downward erosion. The longest lava cave is Kazumura Cave, Hawaii (trunk-length 41 km).
In 2000 and 2001, two large (each ca. 1000 m long) cave systems have been surveyed on the eastern, heavily eroded, flank of Mauna Kea: The Pa‘auhau Civil Defense Cave and the Kuka‘iau Cave (at first called ThatCave/ThisCave System). Both caves occur in the Hamakua Volcanics, 200-250 to 65-70 ka old. They are the first substantial caves documented for lavas of Mauna Kea and the first caves on Hawai‘i showing extensive morphological signs of water erosion.
The Pa‘auhau Civil Defense Cave is a lava tube, as attested by the presence of the typical morphological elements of lava tubes, including secondary ceilings, linings, base sheets, stalactites and lava falls. Subsequently, the cave was modified erosionally by a stream which entered upslope and traversed much, but not all, of the cave, leaving water-falls, water-fall ponds, scallops, gravel, rounded blocks and mud (see paper by Kempe et al., this volume). In contrast the Kuka‘iau Cave – a still active stream cave with a vadose and phreatic section - is essentially erosional in origin. This is concluded from the geology of the strata exposed in the cave and from its morphology: At the upper entrance the cave is situated in a thick series of ‘a‘ā and the lower section was created by removing ‘a‘ā and diamict layers, therefore excluding the possibility that the cave developed from a precursor lava tube. Also, in its phreatic section, the cave makes several right angle turns and moves upward through a series of pāhoehoe sheets, unlike any lava tube. Furthermore, a base layer can be followed along which the major section of the upper cave has developed. Allophane and halloysite – minerals produced by weathering - helped in sealing the primary porosity of this base layer causing a locally perched water table. Water moving along this base layer on a steep hydraulic gradient through the interstices of ‘a‘ā and through small pāhoehoe tubes exerted a high pressure on the porous diamict of the lower cave, causing its erosional removal. Our observations of water erosional caves in lavas of Hawai‘i offer a new perspective on deep-seated water courses in volcanic edifices.
Volcanic gases are a powerful tool for assessing magmatic processes in subduction zones. We report gas chemistry and nitrogen isotope compositions of fumaroles, bubbling springs, and geothermal wells from the Costa Rican segment of the Central American volcanic segment (CAVS), and new correlation spectroscopy (COSPEC) SO2 flux measurements of Poás and Arenal volcanoes. N2/He ratios (100-8,250) and nitrogen isotope compositions (delta15N = -3.02 to +1.690/00) of Costa Rica volatiles are consistent with sources ranging from typical arc-type end-members, with nitrogen addition from the subducting slab, to MORB end-member, having experienced no slab modification. Overall, nitrogen-helium chemistry of Costa Rican material indicates a diminished slab contribution versus other locations along the arc (e.g., Nicaragua and Guatemala). We use SO2 flux measurements of Poás and Arenal (1.80*105 +/- 4.00*104 and 8.30*103 +/- 4.00*103 kg/day, respectively, or 1.30*105 +/- 6.25*104 and 2.81*106 +/- 6.25*105 mol/day, respectively) to extrapolate a SO2 flux for the Costa Rica segment of 1.09*109 mol/day. Using CO2/St (St = total sulfur) of 2.7 and 5.9, we calculate CO2 fluxes of 1.88*108 and 4.11*108 kg/yr, respectively (2.94*109 and 6.42*109 mol/yr, respectively). Other volatile fluxes (N2, He, H2, Ar, HCl, and H2O) are calculated using CO2/St and regional gas chemistry. For Costa Rica, the output/input ratios of nitrogen are less than unity (0.03 to 0.06 for CO2/St of 2.7 and 5.9, respectively), suggesting more N is subducted than released in the subarc, possibly resulting from sediment offscraping, forearc devolatilization, limited fluid availability in the subarc, or subduction past the subarc.
Detailed mapping during the 1991-1993 eruption of Mount Etna has shown that there is a relationship between tumuli, ephemeral vents, lava tubes, and their parent lava flows. During this eruption, many tubes formed in stationary, inflated 'a'a lava flows. Ephemeral vents at the fronts of these stationary flows and above lava tubes fed secondary lava flows, many of which subsequently developed new tubes. The resulting complex network of tubes, ephemeral vents, and secondary flows was responsible for most of the widening, thickening, and lengthening of the 1991-1993 Etna lava flow field. The supply of relatively uncooled lava via tubes to distal parts of this flow field allowed lava to flow 3 km farther from the vent than the longest channel-fed lava flow. Our observations suggest that lava tubes play a more important role in the formation of extensive 'a'a flow fields on Etna than has previously been recognized.
Recognition of the metabolic process of chemosynthesis has recently overthrown the ecological dogma that all life on earth is dependent on sunlight. In complete darkness, complex ecosystems can be sustained by the energy and nutrients provided by chemosynthetic microorganisms. Many of these chemosynthetically-based ecosystems result from microbial manipulation of energy-rich sulfur compounds that can be found in high concentrations in groundwater. Subsurface environments in general can be highly stressful habitats (i.e., darkness, limited food, etc.), but in the case of sulfidic groundwater habitats, organisms must also tolerate and adapt to different stresses (e.g., toxic levels of gases or lethally low oxygen concentrations). Nevertheless, these habitats, and specifically cave and karst aquifers, have a richly diverse fauna. This review focuses on the biodiversity (as the number and types of species) of sulfur-based cave and karst aquifer systems. The relationships among ecosystem productivity, biodiversity, and habitat and ecosystem stresses are explored. The relatively high numbers of species and complex trophic levels could be attributed to the rich and plentiful, chemosynthetically-produced food source that has permitted organisms to survive in and to adapt to harsh habitat conditions. The geologic age and the hydrological and geochemical stability of the cave and karst aquifer systems may have also influenced the types of ecosystems observed. However, similar to non-sulfidic karst systems, more descriptions of the functional roles of karst aquifer microbes and macroscopic organisms are needed. As subterranean ecosystems are becoming increasingly more impacted by environmental and anthropogenic pressures, this review and the questions raised within it will lead to an improved understanding of the vulnerability, management, and sustainability challenges facing these unique ecosystems.
The aseismic Cocos and Carnegie Ridges, two prominent bathymetric features in the eastern Pacific, record ∼20 Myr of interaction between the Galápagos hotspot and the adjacent Galápagos Spreading Center. Trace element data determined by inductively coupled plasma-mass spectrometry in >90 dredged seamount lavas are used to estimate melt generation conditions and mantle source compositions along the ridges. Lavas from seamount provinces on the Cocos Ridge are alkalic and more enriched in incompatible trace elements than any in the Galápagos archipelago today. The seamount lavas are effectively modeled as small degree melts of a Galápagos plume source. Their eruption immediately follows the failure of a rift zone at each seamount province's location. Thus the anomalously young alkalic lavas of the Cocos Ridge, including Cocos Island, are probably caused by post-abandonment volcanism following either a ridge jump or rift failure, and not the direct activity of the Galápagos plume. The seamounts have plume-like signatures because they tap underlying mantle previously infused with Galápagos plume material. Whereas plume heterogeneities appear to be long-lived, tectonic rearrangements of the ridge plate boundary may be the dominant factor in controlling regional eruptive behavior and compositional variations.
Geomorphology of Central America is authored by a scientist with more than 30 years of regional assessment research experience in Central American countries, arming scientists with a classic research method-a method most effective when applied to specific geographic regions globally. The scientific techniques used for assessing regional studies of an area reflect a level of expertise that has become more difficult to come by over the past three decades and underscores the importance of regional assessments of geomorphological features. Complemented with beautifully crafted and exacting maps that capture the region's unique landscapes, Geomorphology of Central America introduces a global vision of the geomorphology and volcanic field of Central America from Guatemala to Panama, making it the first single source of geomorphological content for the region.
Quartz is considered one of the less soluble minerals of the Earth’s crust, and thus hardly affected by chemical weathering. Despite this, since more than forty years, it is clear that the formation of caves and peculiar solutional weathering dominated landforms in quartz-rich lithologies is common and shares several similarities to the well-known karstic ones in carbonate rocks. In the last thirty years great strides have been made in furthering our knowledge of the distribution of these forms around the world, and the geochemical processes involved. These studies have clearly shown that solutional weathering is a fundamental process, acting through interganular dissolution of quartz increasing the rock porosity and decreasing the rock strength to erosion. This process has been described in the concepts of ‘arenization’ and ‘phantomization’ and the widespread evidences of the fundamental role of quartz solution in landform genesis has even developed to the extent of several geomorphologists reassessing the definition of the term ‘karst’, and its application to these peculiar lithologies. Nonetheless the process is complicated by several factors, related both to environmental conditions (water chemistry and availability) as well as to the compositional and textural characters of the lithology (presence of clays, iron hydroxides, carbonate cement, etc.). All these aspects have to be taken carefully in consideration in order to understand if solution is a dominant or accessory process in the landscape evolution. In this review the state of knowledge on the relevant chemical processes, weathering mechanisms, and speleogenesis involved in the surface and underground karstification, and clear examples of quartz solution and solutional landforms from different world locations, are outlined and discussed.
Half-Title PageWiley Series PageTitle PageCopyright PageTable of ContentsPreface and Acknowledgements
A detailed petrographic, structural and morphometric investigation of different types of caves carved in the quartz-sandstones of the “tepui” table mountains in Venezuela has allowed identification of the main speleogenetic factors guiding cave pattern development and the formation of particular features commonly found in these caves, such as funnel-shaped pillars, pendants and floor bumps. Samples of fresh and weathered quartz-sandstone of the Mataui Formation (Roraima Supergroup) were characterised through WDS dispersive X-Ray chemical analyses, picnometer measurements, EDAX analyses, SEM and thin-section microscopy. In all the caves two compositionally different strata were identified: almost pure quartz-sandstones, with content of silica over 95 % and high primary porosity (around 4 %), and phyllosilicate-rich quartz-sandstone, with contents of aluminium over 10 % and low primary porosity (lower than 0.5 %). Phyllosilicates are mainly pyrophyllite and kaolinite. SEM images on weathered samples showed clear evidence of dissolution on quartz grains to different degrees of development, depending on the alteration state of the samples. Grain boundary dissolution increases the rock porosity and gradually releases the quartz grains, suggesting that arenisation is a widespread and effective weathering process in these caves. The primary porosity and the degree of fracturing of the quartz-sandstone beds are the main factors controlling the intensity and distribution of the arenisation process. Weathering along iron hydroxide or silt layers, which represent inception horizons, or a strata-bounded fracture network, predisposes the formation of horizontal caves in specific stratigraphic positions. The loose sands produced by arenisation are removed by piping processes, gradually creating anastomosing open-fracture systems and forming braided mazes, geometric networks or main conduit patterns, depending on the local lithological and structural guidance on the weathering process. This study demonstrates that all the typical morphologies documented in these quartz-sandstone caves can be explained as a result of arenisation, which is guided by layers with particular petrographic characteristics (primary porosity, content of phyllosilicates and iron hydroxides), and different degrees of fracturing (strata-bounded fractures or continuous dilational joints).
The Atirro-Río Sucio fault system forms a major northwest-trending strike-slip fault zone in east-central Costa Rica. We examined the kinematics and temporal evolution of this fault system through geomorphic, structural, and seismologic analysis. This 150-km-long strike-slip fault zone traverses the northern fl ank of the paleovolcanic Cordillera de Talamanca and extends northwestward into the active Cordillera Volcánica Central. Historical seismicity includes frequent minor swarms and occasional moderate-magnitude (M 5.0-6.5) damaging earthquakes. Field geomorphic evidence, fault kinematic data, and earthquake focal mechanisms are consistent in showing dextral slip along the mapped traces of northwest-striking faults. Continuity with other transcurrent faults in northwest Costa Rica indicates that the Atirro-Río Sucio fault system may form the southeastern end of a regional network of northwest-trending dextral faults that accommodate margin-parallel displacement of the Central American forearc sliver. The Atirro-Río Sucio fault system originates within the Central Costa Rica Deformed Belt inboard of the indenting Cocos Ridge. We infer that ridge collision drives lateral escape of crustal fragments northwestward along an array of dextral Central Costa Rica Deformed Belt faults including the major structures of the Atirro-Río Sucio fault system. This zone of arc-parallel extrusion thus represents the root of the Central American forearc sliver. Consistent with recent geodynamic models, we propose that northwestward sliver escape along the Atirro-Río Sucio faults is driven by rigid indentation of the aseismic Cocos Ridge into southern Costa Rica.
Magnetic and bathymetric data from the eastern Pacific have been analyzed and a model for the evolution of the Galapagos region developed. The Farallon plate appears to have broken apart along a pre-existing Pacific-Farallon fracture zone, possibly the Marquesas fracture zone, at about 25 m.y. B.P. to form the Cocos and Nazca plates. This break is marked on the Nazca plate topographically by the Grijalva scarp and magnetically by a rough-smooth boundary coincident with the scarp. The oldest Cocos-Nazca magnetic anomalies parallel this boundary, implying that the early Cocos-Nazca spreading center trended east-northeast. This system soon reorganized into an approximately east-west rise-north-south transform configuration, which has persisted until the present, and the Pacific-Cocos-Nazca triple junction has since migrated north from its original location near lat 5°S. If correct, the combination of these simple geometric constraints produced the " enigmatic" east-trending anomalies south of the Carnegie Ridge. The axes of the Cocos-Nazca spreading center and the Carnegie Ridge are essentially parallel; this can lead to paradoxical conclusions about interpretation of the Cocos and Carnegie Ridges as hotspot tracks. Hey and others (1977) have shown that recent accretion on the Cocos-Nazca spreading center has been asymmetric, resulting at least in part from small discrete jumps of the rise axis. I show here that the geometric objections to both the " hot-spot" and " ancestral-ridge" hypotheses on the origin of the Cocos and Carnegie Ridges can be resolved with an asymmetric-accretion model. However, all forms of the ancestral-ridge hypothesis encounter more severe geometric difficulties, and these results support the hotspot hypothesis.
The well-studied Galápagos Archipelago is a small part of the much larger Galápagos Volcanic Province (GVP) consisting of the Cocos, Carnegie, Coiba and Malpelo aseismic ridges and related seamount provinces. Although these aseismic ridges and seamounts dominate the morphology of the region, little is known about their origin due to a lack of direct age and geochemical information. In order to establish how well the GVP fits with the predictions of the ‘standard’ fixed hotspot and mantle plume hypotheses we conducted a first reconnaissance dredge/grab sampling of submerged regions of the GVP. We present here 40Ar/39Ar ages for many of these new basement samples and evaluate their implications for the various models put forward to explain the origin of the GVP. Correlating new and published sample-site ages with distance from the western side of the Galápagos Islands show that volcanism has not progressed in narrow, time-progressive lines of seamounts and ridges as predicted by the conventional fixed hotspot and mantle plume hypothesis. Rather, volcanism apparently migrated time-progressively across the GVP in broad regions of long-lived and possibly concurrent volcanism. We propose that the most viable explanation for these observations is that the GVP is the product of Cocos and Nazca plate motions across a broad hotspot melt anomaly. The complex spreading history of the Cocos–Nazca spreading centre likely controlled the relative distribution of GVP volcanism between the Cocos and Nazca plates while creating lithosphere of variable age/thickness across the region. While the notion of a broad Galápagos hotspot melting anomaly linked to a complex regional tectonic history requires significant testing it nevertheless highlights the need to test alternative mantle upwelling shapes and sizes compared to the widely accepted notion of a narrow continuous long-lived Galápagos mantle plume conduit defined by the size and location of a Galápagos island.
The occurrences of oceanic assemblages on the Pacific shore of Costa Rica are part of an intricate group of complexes with different tectonic origins. Although they are dismembered and disrupted, they are the only available inland source of information to decipher the evolution of this active margin. Six main regions are described in this paper: (1) Santa Elena Peninsula, constituted by a supra-subduction zone (Santa Elena Nappe), that is overthrusting an igneous-sedimentary Aptian–Cenomanian sequence (Santa Rosa Accretionary Complex), which includes OIB (Ocean Island Basalts) portions, (2) the Nicoya Complex, which is a Jurassic–Cretaceous chert sediment pile disrupted and detached from its original basement by multiple magmatic events that occurred during the formation of the CLIP (Caribbean Large Igneous Province), (3) the Tortugal area formed by the Tortugal Suite with OIB signature and surrounded by Nicoya Complex outcrops, (4) the Herradura Block composed of the Tulín Formation to Maastrichtian to Lower Eocene OIB accreted oceanic island and the Nicoya Complex as basement, (5) Quepos Block correlated with the Tulín Formation, (6) the Osa-Burica Block composed of the Golfito and Burica Terranes (geochemically and chronologically correlated to the Nicoya Complex), Rincón Block (Early Paleocene to Early Eocene accreted seamounts), and the Miocene Osa-Caño Accretionary Complex. The Santa Rosa Accretionary Complex together with the Tortugal Suite have OIB signatures and possibly without Galapagos hotspot geochemical affinity. These coincidences would be explained by the hypothetical existence of an “autochthonous” Cretaceous basement formed by these two regions together with the rest of the Caribbean. Costa Rican basement is constituted by several CLIP portions and seamounts accreted from the end of Cretaceous in the northwest to the Miocene in the southeast, forming the diverse oceanic occurrences of the Pacific, which are mainly connected to the Galapagos hotspot activity.
The dissolution rates of andesitic glass, plagioclase and pyroxene have been calculated for andesitic lava and volcanoclastic material present in a flank aquifer receiving inputs of highly acidic brine from the summit hydrothermal system of Poás Volcano, Costa Rica. Bulk release rates for Na, Ca, Mg and Al along the flow path were calculated by use of solute compositions of acid-chloride-sulfate spring waters located in the Rio Agrio watershed on the NW flank of the volcano, tritium-based residence times and geometric estimates of the reactive surface areas of aquifer rocks. Petrographic data on the composition of interstitial glass and major-mineral phases were used in the mass-balance model NETPATH to calculate individual contributions of glass, plagioclase and pyroxene to the observed mass transfers of Na, K, Ca, Mg, Fe, Al and Si. By assuming that no secondary Al phases were precipitated along the flow path, and assuming a plagioclase composition close to An38, we calculate that solution chemistry of the acid-chloride-sulfate waters of the Rio Agrio watershed is due to dissolution of approximately equal amounts of glass and plagioclase, with most of the Mg and Fe coming from pyroxene dissolution. Calculated rates are typically within one order of magnitude of experimentally-derived rates measured at similar pH and temperatures. In addition, the relative order of mineral reactivity was similar between field- and laboratory-based estimates: pyroxene > plag ⩾ andesitic glass. The good agreement between the field- and laboratory-based estimates is attributed to the interaction of relatively fresh andesite and volcano-clastic material with low-pH fluids of the NW flank aquifer. The largest uncertainty in our calculation is estimation of reactive mineral surface area.
Geología de la hoja Fortuna
- G E Alvarado
Estratigrafía volcánica del Neógeno y Cuaternario
- G E Alvarado
- P Denyer
Mapa geológico de la hoja Murciélago
- P Denyer
- T Aguilar
- E Gazel
Geomicrobiology of secondary mineral deposits coating lava cave walls from Galapagos Islands (Ecuador)
- A Z Miller
- A M Garcia-Sanchez
- M L Coutinho
- Mfc Pereira
- F Gazquez
- J M Calaforra
- P Forti
- J Martínez-Frías
- T Toulkeridis
- A T Caldeira
- C Saiz-Jimenez
Investigaciones de las cuevas marinas de la isla del Coco. Datos de campo
- B T Benumof
- J P Lockwood
Volcanic caves. In: Gunn J (ed) Encyclopedia of caves and karst science
- W R Halliday