Post-Caldera Eruptions at Chalupas Caldera, Ecuador: Determining the Timing of Lava Dome Collapse, Hummock Emplacement and Dome Rejuvenation

Abstract

Determining the lithology, extent, origin, and age of hummocks can be challenging, especially if these are covered by successive deposits and lush vegetation. At Chalupas caldera, a late-Pleistocene silicic center that lies astride the Eastern Cordillera of northern Ecuador, we have tried to overcome these difficulties by combining geological observations and sampling, laboratory analysis (geochemistry, scanning electron microscope analysis and radiometric dating) and remote sensing techniques. Chalupas is the second largest caldera in the Northern Volcanic Zone of South America and its VEI 7 eruption, which occurred ∼0.21 Ma, has garnered the attention of the volcanological community. Our research highlights new observations of the post-caldera activity at Chalupas, beginning with the growth of Quilindaña stratovolcano (∼0.170 Ma), followed by the formation of Buenavista dome that is located 5 km eastward of Quilindaña’s summit. At the eastern foot of Buenavista dome we identify hummocky terrain covering an area of ∼20 km2. Collectively, the suite of techniques that we used helped to highlight geological features that shed light on the provenance of the hummocks and demonstrate that this topography may have originated from gravitational breccia flows from Buenavista lava dome. Numerical simulations were also performed to represent breccia flow transit and emplacement over the present caldera landscape and to view the potential hazard footprints of a future Buenavista dome collapse. For modeling we employed volumes of 20–120 Mm3 to visualize the consecutive traces of mass flow deposition and how the traces correspond to the hummocky landscape. Following the partial collapse of Buenavista lava dome, its rejuvenation is represented by tephra layers of several small eruptions that are dated at about 40 ky BP. These tephras represent some of the youngest eruptive activity recognized at Chalupas caldera. Our results contribute to the overall knowledge about Chalupas and demonstrate that eruptions at this important caldera are more recent than was previously reported.

Timing of Quaternary volcanism and its relationship with tectonics in the central segment of the Ecuadorian Andes

“…In the Eastern Cordillera, several explosive rhyolitic eruptions preceded the construction of the andesitic cone of Cotopaxi II (Hall and Mothes, 2008). The fallout stratigraphic relationships observed in the Eastern Cordillera suggest that the activity of the Huañuna and Rio Valle rhyolitic centers apparently occurred during the Holocene (Mothes and Hall, 2008;Hall et al, 2017b), as well as that of Antisana volcano and the Buenavista dome (Quilindaña volcano; Córdova et al, 2020).…”

“…78°20'W). The Chalupas eruption, dated at 216 ± 5 ka (Bablon et al, 2020b), was followed by the construction of the Quilindaña andesite edifice (4876 m asl) dated at ~184 and ~169 ka Córdova et al, 2020). Several tephra fall deposits older than 43 ka represent its most recent dated activity (Córdova et al, 2020).…”

“…Further south, the Chalupas ignimbrite eruption (VEI 7) occurred southeast of Cotopaxi-I volcano at 216 ± 5 ka (Bablon et al, 2020b), forming a ~17 km-wide caldera and a widespread ignimbrite deposit that covered the Inter-Andean Valley (Mothes and Hall, 2008;Bablon et al, 2020b). The early cone-building stages of Quilindaña volcano, an intra-caldera stratovolcano with activity dated at 184 ± 3 ka (Buenavista dome; groundmass 40 Ar/ 39 Ar age; Córdova et al, 2020;Córdova et al, 2020) and 169 ± 1 ka (plagioclase 40 Ar/ 39 Ar age; , followed the Chalupas eruption.…”

Assessment of geological hazard susceptibility based on remote sensing images

“…In order to quantify the heights of ground objects such as vegetation and buildings, the most common method of analyzing elevation data is to generate Differential DEMs (DoDs) showing pixel-by-pixel differences between multi-temporal DEMs (e.g., to quantify vertical changes in erosion/deposition and buildings), or pixel-by-pixel differences between a digital surface model and a digital terrain model [16,27]. The accuracy of digital elevation models (DEMs) impacts the generation of geomorphic parameters, but high-resolution DEMs do not always ensure high slope and aspect accuracy [28]. In Geographic Information System (GIS) environments, thermal snapshots can be combined with digital photogrammetric data (DEM) for mosaicking and geo-referencing [29].…”

Does the Mineral Composition of Volcanic Ashes Have a Beneficial or Detrimental Impact on the Soils and Cultivated Crops of Ecuador?

“…Volcanism in the Ecuadorian Andes is mainly andesitic in nature and collapsed silicic calderas are infrequent [12]. Eight active volcanoes are located in areas with high agricultural production, characterized and described below in Table 1.…”