Simultaneous effusive and explosive cinder cone eruptions at Veniaminof Volcano, Alaska

Historical eruptions of Veniaminof Volcano, Alaska have all occurred at a 300-m-high cinder cone within the icefilled caldera that characterizes the volcano. At least six of nineteen historical eruptions involved simultaneous explosive and effusive activity from separate vents. Eruptions in 1944, 1983–1984, 1993–1994, 2013, 2018 and 2021 included periods of explosive ash-producing Strombolian activity from summit vents and simultaneous nonexplosive effusion of lava from flank vents on either the southern or northeast sides of the cone. A T-junction conduit network is proposed to explain the simultaneous eruptive styles and as a mechanism for gas-magma segregation that must occur to produce the observed activity. Historical eruptions with simultaneous summit and flank activity produced slightly higher rising ash clouds compared to historical eruptions where simultaneous activity did not occur. This could be a consequence of the partitioning of more gas-charged magma into the vertical conduit of a T-junction conduit system.

KLYUCHEVSKOY VOLCANO: NEW FLANK ERUPTION NAMED AFTER G.S. GORSHKOV, 2021 (KAMCHATKA)

February 18, 2021, a flank eruption started on the north-western slope of the Klyuchevskoy Volcano (Kamchatka, Russia). Cinder cone was formed at the altitude of 2 850 m above sea level, from which a lava flow was spreading north-west. Having moved 1.2 km downslope, the lava flow entered the Ehrmann Glacier, which resulted in the formation of huge mud-stone flows. The latter made their way further north-east along the Kruten’kaya River bed and reached the length of about 30 km. The eruption brought onto the surface high-aluminous basaltic andesites typical of the Klyuchevskoy Volcano. By March 21, the flank eruption ended. It has been named after G.S. Gorshkov, associate member of USSR Academy of Science, famous Russian volcanologist.

INTERPRETASI ANOMALI MEDAN MAGNET BUMI DI KAWASAN GUNUNGAPI LAMONGAN

Lumajang merupakan salah satu kabupaten di Jawa Timur yang terdapat Kawasan Gunungapi Lamongan. Gunungapi Lamongan merupakan Gunungapi monogenesis muda yang tumbuh dari sesar pada puncaknya. Erupsi yang terjadi pada Gunungapi Lamongan tidak hanya pada gunung utama, tetapi juga membentuk kerucut parasit berjumlah sekitar 37 cinder cone dan 27 maar di sekitar gunung utama. Cinder cone dan Maar terbentuk ketika terjadinya kontak antara magma dan air sehingga menimbulkan erupsi freatomagmatik yang disertai dengan muntahan piroklastik dan aliran timbunan material. Penelitian ini berfokus pada pemetaan kawasan Gunungapi Lamongan bagian barat berdasarkan data anomali magnetik untuk mengetahui ada tidaknya aktivitas vulkanik di bawah permukaan Kawasan Gunungapi Lamongan. Berdasarkan analisis hasil penelitian, maka disimpulkan bahwa data anomali magnetik mengonfirmasi adanya suhu tinggi batuan bawah permukaan pada daerah selatan, barat, dan utara dari Gunungapi Lamongan di sekitar maar dan cinder cone yang diindikasikan dengan anomali magnetik negatif. Kata kunci: Gunungapi Lamongan, maar, cinder cone, anomali magnetik.

Studying the distributions of DTM derivatives of cinder cones: a statistical approach in volcanic morphometry

<p>In 2020 we celebrate the 40<sup>th</sup> anniversary of the seminal works of Wood (1980a,b) who was one of the first researchers who considered the shapes of volcanoes in a global point of view. These four decades have seen a number of new approaches that were made possible by the ever increasing computer power and the improvements in Digital Terrain Model (DTM) production. The improving resolution and accuracy of the DTMs of various volcanic fields (VF) opened the way of wide variations of volcanic geomorphometric considerations. However, the differences in approach and, even more importantly, the differences in DTM production technology and resolution make the comparative studies and especially global considerations very difficult.</p><p>We have envisioned a global geomorphometric analytical methodology to analyse cinder cone morphometry in terms of shape versus age: The aim is to establish a relationship between the age of scoria cones age and their morphometry. This is knowingly a rather difficult undertaking and we have made only the first steps yet, but our methodological advancements are always developed with this demand in mind.</p><p>For the sake of diversity, in the current study four volcanic areas were considered with different age ranges, four different resolution DEMs and different number of cones:  San Francisco Volcanic Field, Arizona, USA (SFVF, 30 m horizontal resolution, 313 pcs), the Chaîne des Puys, France (CdP,  0.5 m, 26 pcs), the central-eastern part of the Sierra Chichinautzin, Mexico (SCVF, 5 m, 152 pcs) and Kula Volcanic Field, Turkey (KVF, 12.5 m, 64 pcs). As age data we had either age ranges or measured ages of the individual cones.</p><p>A great number of derivatives (mostly related to slope angles) have been calculated for the individual cones. Their most important statistics and their distribution were computed. Irregularities and, especially, cone degradation modify the original statistical distribution; these distributions can be compared in statistical way. A quantitative distance (metric) has been introduced to study the similarity or dissimilarity of the cones.</p><p>For the comparison, we have grouped the cones in several ways – they have been observed individually, by areas and by age groups (based on previous researches). For every cone boxplot diagrams, histograms and cumulative histograms were made to detect differences together with average and median values. These age groups were subjects of the Mann – Whitney statistical test to discriminate statistically independent or dependent samples in the populations. The test showed some clear relations between erosion (shape) and age.</p><p>We created a cinder cone viewer for visualization purposes. This tool can display the aforementioned distributions and helps in picking pairs or groups of cinder cones to compare. As expected, the intra-VF comparisons are typically more successful as inter-VF comparisons. However, promising new morphometric derivatives (e.g., sectorial distributions) are under development.</p><p>Wood, C. A.: Morphometric evolution of cinder cones, J. Volcanol. Geoth. Res., 7, 387–413, 1980a.</p><p>Wood, C. A.: Morphometric analysis of cinder cone degradation, J. Volcanol. Geoth. Res., 8, 137–160, 1980b.</p>