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Research about El Salvador

Source-linked reports with geographic coverage including El Salvador.

17 recordsLinked to original sources
USGS2023

Ash aggregate-rich pyroclastic density currents of the 431 CE Tierra Blanca Joven eruption, Ilopango caldera, El Salvador

The VEI 6, Tierra Blanca Joven pyroclastic sequence (30–90 km 3 DRE volume), erupted from Ilopango caldera, El Salvador, in 431 CE, is the product of one of the largest eruptions of the last two millennia. The eruption devastated Central America's Mayan civilization. The eruption began with a short-lived phase of ash and pumice fall deposition and transitioned to a ‘wet’ explosive phase during which pyroclastic density currents flowed >40 km from the caldera. Detailed field and sedimentological analyses are provided for the deposits of ash-aggregate-rich pyroclastic density currents generated during early phases of the eruption. The first phase of pyroclastic density current inundation incinerated forests and deposited up to 30 m of, non-welded, ash-rich ignimbrite in proximal regions, along with ash fall layers of co-ignimbrite origin. Following fallout of a thin layer of pumice and lithic lapilli, a second phase of pyroclastic density current inundation and co-ignimbrite ash fall commenced. A range of ash aggregate types is present in the pyroclastic density current deposits and interbedded co-ignimbrite ash fall layers. Whole and broken concentrically layered ash aggregates (accretionary lapilli) reach >50 vol% in some horizons within some beds in the pyroclastic density current deposits. The evidence indicates that the ash aggregates grew within overriding co-ignimbrite ash plumes and subsequently fell into ground-hugging currents. Our findings suggest that the aggregate-rich nature of the pyroclastic density current deposits originated through incorporation of lake water into eruptive plumes, which in turn triggered rapid, pervasive aggregation within ash clouds and co-ignimbrite plumes.

Ilopango caldera↗
USGS2022

Growth of complex volcanic ash aggregates in the Tierra Blanca Joven eruption of Ilopango Caldera, El Salvador

Aggregation processes control both the residence time and dispersal of volcanic ash during eruptions yet remain incompletely understood. The products of aggregation vary from simple ash clusters to large, complexly layered accretionary lapilli. Here we detail the micro-stratigraphy of a single population of accretionary lapilli that grew during the ∼431 CE Tierra Blanca Joven eruption from Ilopango Caldera, El Salvador. The accretionary lapilli were sampled 10 km from the caldera source within a sequence of ash-rich pyroclastic density current deposits and intercalated fall material, known as unit D, which is traceable >40 km from Ilopango. Scanning electron microscopy and image analysis reveal common facies that form distinct layers within the accretionary lapilli. Each facies is distinguished by quantitative and qualitative variations in particle size distribution , porosity, and particle fabric. We infer that these textures resulted from aggregation conditions that differed in terms of liquid water availability, particle concentration and grain size distributions. In our proposed model, a characteristic sequence of facies accreted from core to rim in the accretionary lapilli during passage through ash clouds generated by vent-derived plumes and pyroclastic density currents. The accretionary lapilli are mostly composed of smaller aggregates (ash clusters, ash pellets) and grew predominantly by accretion of already-formed aggregates, rather than by grain-by-grain accretion of individual particles. This finding is consistent with observations of rapid aggregate growth in volcanic plumes, suggesting a common evolutionary pathway for accretionary lapilli formation across diverse eruptions.

Ilopango caldera↗
USGS2022

Nuevos datos: Avalancha de escombros de Acajutla, volcán Santa Ana

The Acajutla debris-avalanche deposit is dated to about 40,000 cal BP. The dating is based on two 14C dates on pieces of wood from the debris-avalanche deposit recovered from a core at the Santa Águeda School Center. The debris-avalanche deposit overlies a 1.2-m-thick paleosol and four ash layers. One of these ash layers is geochemically correlated to the Los Chocoyos ash from Atitlán Caldera, while the others are possibly from eruptions of Coatepeque and Ilopango Calderas. The new data, collected in well reports from the years 1966 to 2019, include deposit thicknesses identified in 25 wells for water monitoring, bathymetric data from nautical charts, GEBCO’s grids, updated topographic data from LIDAR, and a reassessment of the deposit’s lateral limits. This new data will allow us to better constrain the volume of the Acajutla debris-avalanche deposit.

Conference Paper↗
USGS2022

Estratigrafía preliminar del flanco Este del volcán de Santa Ana

We present the eruption sequence for the east flank of Santa Ana volcano, which we divide into the sections above and below the Tierra Blanca Joven (TBJ) formation. The sequence below the TBJ suggests a series of mafic magmatic eruptions that began before 7,800 cal BP and continued until after 5,800 cal BP. These eruptions emplaced tephra-fall and pyroclastic-density-current deposits. The sequence above the TBJ are deposits from recent eruptions during the last 1.5 ky. Most of these eruptions were phreatomagmatic with associated pyroclastic surges. The two sequences demonstrate a shift in eruptive style possibly related to an increase in water volume in the hydrothermal system.

Santa Ana volcano↗
USGS2019

Radiocarbon and geologic evidence reveal Ilopango volcano as source of the colossal 'mystery' eruption of 539/40 CE

Ilopango volcano (El Salvador) erupted violently during the Maya Classic Period (250–900 CE) in a densely-populated and intensively-cultivated region of the southern Maya realm, causing regional abandonment of an area covering more than 20,000 km 2 . However, neither the regional nor global impacts of the Tierra Blanca Joven (TBJ) eruption in Mesoamerica have been well appraised due to limitations in available volcanological, chronological, and archaeological observations. Here we present new evidence of the age, magnitude and sulfur release of the TBJ eruption, establishing it as one of the two hitherto unidentified volcanic triggers of a period of stratospheric aerosol loading that profoundly impacted Northern Hemisphere climate and society between circa 536 and 550 CE. Our chronology is derived from 100 new radiocarbon measurements performed on three subfossil tree trunks enveloped in proximal TBJ pyroclastic deposits. We also reassess the eruption magnitude using terrestrial (El Salvador, Guatemala, Honduras) and near-shore marine TBJ tephra deposit thickness measurements. Together, our new constraints on the age, eruption size (43.6 km 3 Dense Rock Equivalent of magma, magnitude = 7.0) and sulfur yield (∼9–90 Tg), along with Ilopango's latitude (13.7° N), squarely frame the TBJ as the major climate-forcing eruption of 539 or 540 CE identified in bipolar ice cores and sourced to the tropics. In addition to deepening appreciation of the TBJ eruption's impacts in Mesoamerica, linking it to the major Northern Hemisphere climatic downturn of the mid-6th century CE offers another piece in the puzzle of understanding Eurasian history of the period.

Guazapa↗
USGS2014

Appendix F—Ground‐water studies in Central America

In June, 1943, the United States Geological Survey assigned two ground‐water geologists, A. N. SAYRE and G. C. TAYLOR, Jr., to study water‐supply problems in Central America for the Coordinator of Inter‐American Affairs and to make recommendations for remedial measures to provide water for cities and towns, especially along the Inter‐American Highway. El Salvador, where a large number of towns along the highway have serious water‐shortages during the six‐month dry season from December to June, was selected as the country in which most of the work was to be done. The Direccion de Sanidad de Salvador, through its Director, Dr. V. A. SUTTER, provided a list of some 35 cities which suffered the most serious water‐shortages and each of these cities was visited. The geological and ground‐water conditions in the vicinity were studied by reconnaissance‐methods and remedial measures were recommended. In nearly every case the water‐shortage was due in large part to improper or incomplete development of the available supplies. Most municipalities obtained their water‐supplies from springs which either had inadequate flow or were improperly developed. In a few cases the spring‐flow was adequate but a large quantity of water was wasted either through poor distribution‐systems or through breaks in the line that conducted water from the spring to the city. Nearly all of the water works were unsanitary. In most places it appeared likely that adequate supplies can be obtained from wells at relatively shallow depth. In some places adequate supplies can be obtained by proper improvements of springs that are now in use. In a very few cases no remedy for the shortage of water could be suggested.

Central America↗
USGS2014

Aspidoscelis deppii (black-bellied racerunner). Predation by turkey vulture.

Aspidoscelis deppii is widely distributed from Veracruz and Michoacan, Mexico, to Costa Rica (Köhler et al. 2006. The Amphibians and Reptiles of El Salvador, Krieger Publishing Company, Malabar, Florida. 238 pp.). Neotropical lizards are abundant and common prey to all classes of terrestrial vertebrates, and bird predation of lizards is well known. The Turkey Vulture (Carthartes aura) is widely distributed from southern Canada south to South America and is present throughout the entire range of A. deppii, where it occupies a variety of open and forested habitats and feeds opportunistically on a wide range of wild and domestic carrion. While almost exclusively a scavenger, this species is known to rarely kill small animals or invertebrates (Kirk and Mossman 1998. In A. Poole [ed.], The Birds of North America Online. Cornell Lab of Ornithology, Ithaca; accessed 15 August 2013). An adult Turkey Vulture was collected during avian control to minimize wildlife hazards at the Aeropuerto Internacional de El Salvador (ca. 50 km SE of San Salvador, 13.4408°N 89.0556°W; datum WGS84) on 10 July 2012 and subsequently cataloged (USNM 646876) in the Bird Division at the National Museum of Natural History (NMNH) in Washington, DC. Dissection during preparation of the bird as a museum specimen revealed a male A. deppii (ca. 56 mm SVL) in the stomach. It was cataloged at the NMNH in the Division of Amphibians and Reptiles (USNM 580989). Tissue samples were removed from both the lizard and the bird and deposited in the biorepository at the NMNH. To the best of our knowledge, this is the first documented record identifying A. deppii as a prey item of the Turkey Vulture.

Aeropuerto Internacional de El Salvador↗
USGS2004

Seismicity and tectonics of El Salvador

The large-scale plate-tectonics framework of El Salvador was defined in the “plate-tectonics revolution” of the 1960s and 1970s, but important issues related to seismic hazards depend on details that have been only recently, or are not yet, understood. Present evidence suggests that coupling across the interface-thrust zone beneath coastal El Salvador is sufficient to produce occasional interface-thrust earthquakes as large as M ∼8. The rate of such earthquakes is determined by the percentage of relative plate motion that is accumulated as elastic strain on the thrust-fault interface between the Cocos and Caribbean plates, which appears to be lower than in many other subduction zones, but is not well established. Earthquakes in the interior of the Cocos plate, such as the El Salvador earthquake of January 13, 2001, account for a significant percentage of Wadati-Benioff zone earthquakes. Separate consideration of the seismic hazard posed by, respectively, Cocos intraplate earthquakes and interface-thrust earthquakes is complicated by the difficulty of separating interface-thrust and Cocos intraplate events in earthquake catalogs. Earthquakes such as the San Vicente–San Salvador sequence of February 13–25, 2001, probably result from the motion of the Central American forearc northwestward with respect to the interior of the Caribbean plate; the geometry of the fault systems that accommodate the motion remains to be worked out. Understanding of this tectonic complexity and associated seismic hazards will be facilitated greatly by the long-term operation of high-sensitivity local seismograph networks, such as that operated by, and currently being upgraded by, the Servicio Nacional de Estudios Territoriales (SNET) of El Salvador.

Special Papers of the Geological Society of Americ↗
USGS2004

Landslides triggered by the 13 January and 13 February 2001 earthquakes in El Salvador

During a one-month period in early 2001 , El Salvador experienced two devastating earthquakes . On 13 January , a M-7.7 earthquake centered ∼40 km off the southern coast in the Pacific Ocean caused widespread damage and fatalities throughout much of the country. The earthquake triggered thousands of landslides that were broadly scattered across the southern half of the country. The most damaging landslide , a rapidly moving mass of ∼130, 000 m 3 , occurred in the Las Colinas neighborhood of Santa Tecla, where ∼585 people were killed. Another large landslide (∼750, 000 m 3 ) near the city of San Vicente blocked the Pan-American Highway for several weeks. One month later, on 13 February , a M-6.6 earthquake occurred ∼40 km east-southeast of San Salvador and triggered additional thousands of landslides in the area east of Lake Ilopango. The landslides were concentrated in a 2500 km 2 area and were particularly abundant in areas underlain by thick deposits of poorly consolidated, late Pleistocene and Holocene Tierra Blanca rhyolitic tephras erupted from Ilopango caldera. Most of the triggered landslides were relatively small, shallow failures, but two large landslides occurred that blocked the El Desagüe River and the Jiboa River. The two earthquakes triggered similar types of landslides , but the distribution of triggered landslides differed because of different earthquake source parameters. The largemagnitude, deep, offshore earthquake triggered broadly scattered landslides over a large region, whereas the shallow, moderate-magnitude earthquake centered within the country triggered a much smaller, denser concentration of landslides . These results are significant in the context of seismic-hazard mitigation for various earthquake scenarios.

Special Paper of the Geological Society of America↗
USGS2001

Observations and recommendations regarding landslide hazards related to the January 13, 2001 M-7.6 El Salvador earthquake

The January 13, 2001 earthquake (M-7.6) off the coast of El Salvador triggered widespread damaging landslides in many parts of the El Salvador. In the aftermath of the earthquake, the Salvadoran government requested technical assistance through the U.S. Agency for International Development (USAID); USAID, in turn, requested help from technical experts in landslide hazards from the U.S. Geological Survey. In response to that request, we arrived in El Salvador on January 31, 2001 and worked with USAID personnel and Salvadoran agency counterparts in visiting landslide sites and evaluating present and potential hazards. A preliminary, unofficial report was prepared at the end of our trip (February 9) to provide immediate information and assistance to interested agencies and parties. The current report is an updated and somewhat expanded version of that unofficial report. Because of the brief nature of this report, conclusions and recommendations contained herein should be considered tentative and may be revised in the future.

Open-File Report↗
USGS2001

Volcano hazards in the San Salvador region, El Salvador

San Salvador volcano is one of many volcanoes along the volcanic arc in El Salvador (figure 1). This volcano, having a volume of about 110 cubic kilometers, towers above San Salvador, the country’s capital and largest city. The city has a population of approximately 2 million, and a population density of about 2100 people per square kilometer. The city of San Salvador and other communities have gradually encroached onto the lower flanks of the volcano, increasing the risk that even small events may have serious societal consequences. San Salvador volcano has not erupted for more than 80 years, but it has a long history of repeated, and sometimes violent, eruptions. The volcano is composed of remnants of multiple eruptive centers, and these remnants are commonly referred to by several names. The central part of the volcano, which contains a large circular crater, is known as El Boquerón, and it rises to an altitude of about 1890 meters. El Picacho, the prominent peak of highest elevation (1960 meters altitude) to the northeast of the crater, and El Jabali, the peak to the northwest of the crater, represent remnants of an older, larger edifice. The volcano has erupted several times during the past 70,000 years from vents central to the volcano as well as from smaller vents and fissures on its flanks [1] (numerals in brackets refer to end notes in the report). In addition, several small cinder cones and explosion craters are located within 10 kilometers of the volcano. Since about 1200 A.D., eruptions have occurred almost exclusively along, or a few kilometers beyond, the northwest flank of the volcano, and have consisted primarily of small explosions and emplacement of lava flows. However, San Salvador volcano has erupted violently and explosively in the past, even as recently as 800 years ago. When such eruptions occur again, substantial population and infrastructure will be at risk. Volcanic eruptions are not the only events that present a risk to local communities. Another concern is a landslide and an associated debris flow (a watery flow of mud, rock, and debris--also known as a lahar) that could occur during periods of no volcanic activity. An event of this type occurred in 1998 at Casita volcano in Nicaragua when extremely heavy rainfall from Hurricane Mitch triggered a landslide that moved down slope and transformed into a rapidly moving debris flow that destroyed two villages and killed more than 2000 people. Historical landslides up to a few hundred thousand cubic meters in volume have been triggered on San Salvador volcano by torrential rainstorms and earthquakes, and some have transformed into debris flows that have inundated populated areas down stream. Destructive rainfall- and earthquake-triggered landslides and debris flows on or near San Salvador volcano in September 1982 and January 2001 demonstrate that such mass movements in El Salvador have also been lethal. This report describes the kinds of hazardous events that occur at volcanoes in general and the kinds of hazardous geologic events that have occurred at San Salvador volcano in the past. The accompanying volcano-hazards-zonation maps show areas that are likely to be at risk when hazardous events occur again.

San Salvador↗
USGS2001

Volcano-hazard zonation for San Vicente volcano, El Salvador

San Vicente volcano, also known as Chichontepec, is one of many volcanoes along the volcanic arc in El Salvador. This composite volcano, located about 50 kilometers east of the capital city San Salvador, has a volume of about 130 cubic kilometers, rises to an altitude of about 2180 meters, and towers above major communities such as San Vicente, Tepetitan, Guadalupe, Zacatecoluca, and Tecoluca. In addition to the larger communities that surround the volcano, several smaller communities and coffee plantations are located on or around the flanks of the volcano, and major transportation routes are located near the lowermost southern and eastern flanks of the volcano. The population density and proximity around San Vicente volcano, as well as the proximity of major transportation routes, increase the risk that even small landslides or eruptions, likely to occur again, can have serious societal consequences. The eruptive history of San Vicente volcano is not well known, and there is no definitive record of historical eruptive activity. The last significant eruption occurred more than 1700 years ago, and perhaps long before permanent human habitation of the area. Nevertheless, this volcano has a very long history of repeated, and sometimes violent, eruptions, and at least once a large section of the volcano collapsed in a massive landslide. The oldest rocks associated with a volcanic center at San Vicente are more than 2 million years old. The volcano is composed of remnants of multiple eruptive centers that have migrated roughly eastward with time. Future eruptions of this volcano will pose substantial risk to surrounding communities.

Guadalupe;San Vicente;Tecoluca;Tepetitan;Zacatecol↗
USGS2001

Lahar-hazard zonation for San Miguel volcano, El Salvador

San Miguel volcano, also known as Chaparrastique, is one of many volcanoes along the volcanic arc in El Salvador. The volcano, located in the eastern part of the country, rises to an altitude of about 2130 meters and towers above the communities of San Miguel, El Transito, San Rafael Oriente, and San Jorge. In addition to the larger communities that surround the volcano, several smaller communities and coffee plantations are located on or around the flanks of the volcano, and the PanAmerican and coastal highways cross the lowermost northern and southern flanks of the volcano. The population density around San Miguel volcano coupled with the proximity of major transportation routes increases the risk that even small volcano-related events, like landslides or eruptions, may have significant impact on people and infrastructure. San Miguel volcano is one of the most active volcanoes in El Salvador; it has erupted at least 29 times since 1699. Historical eruptions of the volcano consisted mainly of relatively quiescent emplacement of lava flows or minor explosions that generated modest tephra falls (erupted fragments of microscopic ash to meter sized blocks that are dispersed into the atmosphere and fall to the ground). Little is known, however, about prehistoric eruptions of the volcano. Chemical analyses of prehistoric lava flows and thin tephra falls from San Miguel volcano indicate that the volcano is composed dominantly of basalt (rock having silica content <53%), similar to the lava erupted by Hawaiian volcanoes. The chemical composition of eruptive products and the lack of evidence of large cataclysmic eruptions suggests that prehistoric eruptions probably were similar in nature to the historical eruptions. Unlike San Salvador and San Vicente volcanoes, San Miguel volcano does not appear to have had a history of violent explosive eruptions.

El Transito;San Jorge;San Miguel;San Rafael Orient↗
USGS1982

Progress of the seismological program in El Salvador

El Salvador is located in Central America at the axis of geographical coordinates 14 &deg; north latitude and 89&deg; west longitude. Situated inside the circumpacific "ring of fire" it is thus vulnerable to sudden earthquakes and volcanic eruptions. Since 1520, El Salvador has sustained approximately 40 destructive earthquakes, an average of one earthquake every 11.4 years. The interval of time between earthquakes during the centuries, however, has been variable. For instance, given the importance of San Salvador as a city since the beginning of the 16th century, it shows historically that over any 100-year interval, there have been four catastrophic earthquakes in the region. During the 20th century, there have been already three large earthquakes in the region. During the 20th century, there have been already three large earthquakes in 1917, 1919, and 1965. If a recurrence of four earthquakes per century is a valid premise, then one may expect another large destructive earthquake before the end of this century. In the following sections, a summary of the seismological programs in El Salvador, their present status, and programs proprosed for the future are discussed.

Earthquake Information Bulletin (USGS)↗