After eight years of quiescence, Fernandina volcano experienced two short-lived eruptions, on 4 September 2017 and 16 June 2018. The eruptions were characterized by very short periods of unrest that started a few hours before the initiation of the eruptive activity. On the other hand, Sierra Negra volcano (Isabela Island) began a new eruptive period on 26 June 2018, after almost one year of persistent unrest characterized by an increase in the magnitude and number of seismic events and more than 5 meters of uplift since its last eruption in 2005. The Sierra Negra and Fernandina eruptions were located in remote zones where access is extremely complex. Thus, satellite images complement the continuous monitoring data of the Instituto Geofísico (IG-EPN) with remote observations and allow rapid response mapping in order to identify the areas affected by the lava flows. Finally, the aim of this Report is to encourage other scientists to investigate the behaviors of both pre-eruptive and eruptive periods registered during these eruptions. ResumenDespués de ocho años de reposo, el volcán Fernandina experimentó dos periodos eruptivos de corta duración, el 4 de Septiembre del 2017 y el 16 de Junio del 2018. Dichas erupciones se caracterizaron por etapas muy cortas de agitación que iniciaron pocas horas antes de la erupción. Por otro lado, el volcán Sierra Negra, localizado en la Isla Isabela, inició un nuevo periodo eruptivo el 26 de Junio del 2018, después de casi un año de persistente agitación caracterizada por el incremento en la magnitud y número de eventos sísmicos y más de cinco metros de levantamiento del piso de la caldera desde su última erupción en 2005. Las erupciones de Sierra Negra y Fernandina se localizaron en zonas remotas, donde el acceso es extremadamente difícil. Es así que, imágenes satelitales complementaron el monitoreo continuo realizado por el Instituto Geofísico (IG-EPN) y permitieron identificar las zonas afectadas por los flujos de lava. Finalmente, uno de los propósitos de este reporte es alentar a otros científicos a investigar el funcionamiento de estos volcanes durante las etapas pre-eruptivas y eruptivas registradas.
[1] The Panama Triple Junction (Cocos-Nazca-Caribbean) represents the point that abruptly separates the thick and rapidly subducting Cocos plate to the northwest from the thin and obliquely subducting Nazca plate to the southeast along the Central American convergent margin. New structural and geomorphic analyses on the Burica Peninsula, an outer fore-arc peninsula located only ∼100 km inboard the Panama Triple Junction, reveal that the peninsula is dominated primarily by contractional deformation along three listric thrust faults that root in the underlying plate boundary. The geometry and spatial distribution of these thrusts indicate that this deformation occurs primarily in response to the change in crustal thickness occurring as a result of eastern migration of the flank of the Cocos Ridge coeval with migration of the Panama Triple Junction at a rate of ∼55 mm/yr to the southeast. Mapping and detailed elevation surveys reveal eight marine terraces on the peninsula with a distribution of inner edge elevations indicating that uplift is spatially uniform from north to south along strike in this area. However, terraces along the northwest part of the peninsula are offset across major thrust faults. Age control provided by 14 C, OSL and soil chronosequences indicate that the terraces within the easternmost portion of the peninsula range in age from Marine Isotope Stage (MIS) 3 to Holocene, a result that indicates that this portion of the peninsula is younger than ∼60 ka. Time-averaged uplift rates calculated from marine terraces and other Quaternary marine deposits yield consistent uplift rates that range between 2.1 ± 0.1 and 7.7 ± 0.5 mm/yr for samples older than 1 ka and between 6.9 ± 1.0 and 19.3 ± 8.0 mm/yr for samples younger than 1 ka. We interpret this temporal distribution in uplift rates to suggest that the eight terraces preserved on the peninsula are produced coseismically wherein the anomalously high uplift rates calculated from the youngest samples (<1 ka) are not yet averaged over a complete seismic cycle. These observations, combined with (1) shortening estimates from balanced cross sections indicating that minimum shortening decreases from northwest to southeast and (2) the observation of growth strata within the youngest marine units, are consistent with a space-for-time model for triple junction migration. These results indicate that both triple junction migration and the change in bathymetry occurring at the triple junction boundary are far more dominant factors in outer fore-arc deformation than the change in rate and obliquity of subduction and basal tractions that also occur on either side of the triple junction.
The value of field trips is undisputed across disciplines. Field-site visits whether in social or physical sciences provide grounding for place- and discovery-based learning. Yet field trips have limitations that can now be overcome by the promise of immersive technologies that can improve quality and accessibility. This promise is twofold: First, we can harness advancements made in sensing technologies to create immersive experiences of places across the earth efficiently; second, we can provide detailed empirical evaluations on immersive learning and quantify educational value. We report on a study that splits an introductory geosciences course into two groups with one group experiencing a traditional field trip, while a second group visits the same site virtually, immersing the students in the site using a head-mounted device. Results show the advantages of virtual field trips (VFTs) concerning enjoyment, learning experience, and actual lab scores. We embed the discussion of these results into a more general assessment of the advantages of VFTs and a taxonomy of VFTs as a basis for future studies.
The expansion of geodetic networks and Earth observing systems has allowed for new understandings of continental transform faults, including the partitioning of relative plate motions between multiple active strands and fault behavior during the earthquake cycle. One important global observation is that some continental transform faults creep (i.e., slip aseismically) at a percentage of or even at the full relative plate motion rate. The Caribbean-South American plate boundary is a right-stepping, segmented, dextral continental transform system. We studied active faults in the Trinidad-Tobago segment of the Caribbean-South American plate boundary zone using a new GPS-derived horizontal velocity field, then modeled these data using a series of simple screw dislocation models. Our best-fit model for interseismic strain accumulation requires 13.4 ± 0.3 mm/yr of right-lateral movement and very shallow locking (0.2 ± 0.2 km), essentially creep, across the Central Range Fault (CRF), 3.4 ± 0.3 mm/yr across the South Coast Fault south of Trinidad, and 3.5 ± 0.3 mm/yr of dextral shear on fault(s) between Trinidad and Tobago. The CRF creeps along a physical boundary between rocks associated with thermogenically generated petroleum in south and central Trinidad and rocks containing only biogenic gas to the north. Fluid (oil and gas) overpressure, in addition to weak material in the fault core, likely causes CRF creep. Plain Language SummaryWe used GPS-derived horizontal velocities to study active faulting in Trinidad and Tobago, which span the Caribbean-South American transform plate boundary. The principal transform fault, the Central Range Fault, accommodates 12-15 mm/yr (~70%) of the total plate motion via creep. Secondary fault zones north and south of Trinidad each accommodate~3.5 mm/yr of the remaining dextral shear. Creep on the Central Range Fault may be due to petroleum overpressures.
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