Weathering of Volcanic Ash in the Cryogenic Zone of Kamchatka, Eastern Russia

Clay Minerals, (2014) 49, 195–212 OPEN ACCESS Weathering of volcanic ash in the cryogenic zone of Kamchatka, eastern Russia 1, 2 E. KUZNETSOVA * AND R. MOTENKO 1 SINTEF Building and Infrastructure, Trondheim, NO-7465, Norway, and 2 Lomonosov Moscow State University, Moscow, 119991, Russia (Received 8 August 2012; revised 28 August 2013; Editor: Harry Shaw) ABSTRACT: The nature of the alteration of basaltic, andesitic and rhyolitic glass of Holocene and Pleistocene age and their physical and chemical environments have been investigated in the ash layers within the cryogenic soils associated with the volcanoes in the central depression of Kamchatka. One of the main factors controlling the alteration of the volcanic glass is their initial chemistry with those of andesitic (SiO2 =53À65 wt.%) and basaltic (SiO2 < 53 wt.%) compositions being characterized by the presence of allophane, whereas volcanic glass of rhyolitic composition (SiO2>65 wt.%) are characterized by opal. Variations in the age of eruption of individual ashes, the amount and nature of the soil water, the depth of the active annual freeze-thawing layer, the thermal conductivity of the weathering soils, do not play a controlling role in the type of weathering products of the ashes but may affect their rates of alteration. KEYWORDS: volcanic ash, allophane, opal, unfrozen water, thermal conductivity, permafrost, Kamchatka. The highly active volcanic area of Kamchatka in local and remote eruptions and from the secondary eastern Russia is part of the circum-Pacific belt of re-deposition of ash (Bazanova et al., 2005). andesitic volcanism. It is situated north of the 49th Considerable research has been carried out on the parallel of latitude and is characterized by a weathering of volcanic glass. For volcanic ash soils severely cold climate with permafrost widespread in warm humid climates Wada & Wada (1977) above an altitude of 700 m. The Kamchatka suggested that the sequence of weathering is peninsula is blanketed by a soil-pyroclastic cover volcanic glass ? allophane ? halloysite or (Melekestsev et al., 1969) consisting of loose, volcanic glass ? opal ? allophane ? halloysite. pyroclastic material from explosive eruptions and For the rhyolitic glass in the humid conditions in buried soil beds. Ashes from major eruptions form Japan, the allophane ? halloysite transformation clear marker horizons and can be traced over wide occurs after 6000 years (Wada & Wada, 1977; areas. This has allowed a well defined tephro- Nagasawa, 1978; Wada, 1989). However, other stratigraphy to be established that is based upon the studies have shown that, depending on their chemical signature of the glass (Braitseva et al., different glass compositions, volcanic ash may 1997). Between the key ash marker horizons are weather directly to halloysite as well as to other pyroclastic deposits derived from both minor allophane (Parfitt et al., 1983; Parfitt & Wilson, 1985). Basaltic glass (SiO2:Al2O3 <4)hasan intrinsically smaller molar Si:Al ratio and a soft and porous structure that favours weathering at a much * E-mail: [email protected] higher rate than rhyolitic glass (SiO2:Al2O3 =5to DOI: 10.1180/claymin.2014.049.2.04 6) (Lowe, 1986). # 2014 The Mineralogical Society Downloaded from http://pubs.geoscienceworld.org/claymin/article-pdf/49/2/195/3301715/gsclaymin.49.2.04-kuz_OA.pdf by guest on 24 September 2021 196 E. Kuznetsova and R. Motenko The influence of climatic variation on the There are from six to eight soil profiles weathering of volcanic glass is still to be clarified, developed in the soil-pyroclastic cover associated particularly in the extremely cold climates asso- with these volcanoes. In each there is an organic ciated with high precipitation. In this paper we horizon that overlies volcanic ash. The soils have a report on our study of the breakdown of volcanic small humus content ~ 1 to 2.4%, which is not glass in the soil-pyroclastic cover associated with typical for most volcanic soils of Kamchatka the Klyuchevskaya group of volcanoes situated in (Zakharikhina, 2009); this reflects the interplay of the Central Depression of Kamchatka (55À56ºN, permafrost, relatively low rainfall and the abundant 160À161ºE). The group consists of several active deposition of airborne volcanic material. volcanoes (Klyuchevskoy (~4800 m), Bezymianny (~2900 m), Ushkovsky (~3900 m), Plosky ANALYTICAL METHODS. Tolbachik (~3100 m) plus ten others that are not active today, together with numerous small cinder A total of 24 samples (Table 1) were collected at cones, extrusive domes and other volcanic features elevations between 130 and 1630 m. Samples 1-6 (Braitseva et al., 1995). It is the location where the were collected from the active layer in the thawed Large Fissure Tolbachik Eruption took place in state, sample 7 in the frozen state from a depth of 1975 and 1976, during which about 500 km2 were 2.50 m in a drill hole and other samples from the covered by scoria and ash and 3 new cinder cones frozen active layer. and lava fields were formed (Fedotov & Markhinin, The moisture content (ratio of the mass of water 1983). to the mass of dry sample) was determined by The climate of the study area is characterized by drying the wet samples at 105ºC for 12 h. Adsorbed cold winters, as well as mild and wet summers that water was determined by drying samples to constant are mainly influenced by cyclonic activity. No weight from room temperature to 105ºC. permanent meteorological station exists in the Thermal studies (TG, DTG, DTA analyses) were mountainous areas, but the Klyuchi station (WMO carried out using a Q-1500D derivatograph over the 32389), situated in the Kamchatka river valley at an range from room temperature to 1000ºC with a elevation of 29 m and about 30À40 km from the heating rate of 20ºC/min (Topor et al., 1987). The central part of volcanic area, provides a long-term loss of absorbed (low) water over the range from climatic record for the region. The mean annual room temperature to 110ºC was observed on the average temperature in Klyuchi is À0.7ºC for heating curves of the samples (3, 4, 8, 9, 13, 15, 17, 1910À2007 and ~0ºC for 1970À2007. The total 24), and the endothermic effects recorded over the annual precipitation in Klyuchi is ~500 mm, range from 110 to 750ºC corresponded to the loss whereas in the mountains it is estimated to be of structural (high) water by the ash material. The ~1000 mm (Muravyev, 1999). In Klyuchi the snow total mass loss (structural water + absorbed water) cover usually lasts from October to June with a is designated as Wterm and its values are shown in snow cover thickness of ~1.5À3 m in forested areas Table 6. and 50À80 cm or less in open areas due to From the weight difference between the wet and redistribution by strong winds (Abramov et al., dried sample and the volumes of the sample, the dry 2008). bulk density and water content were calculated. Permafrost and periglacial processes are wide- Solid particle density (mineral density of rock) was spread. The lower boundary of the permafrost is at measured for rock powder on an exclusive device 750À900 m above sea level for the northern slopes ELA (Kalachev et al., 1997). The underlying and 650À800 m for the southern ones. Numerous principle of this device is the law of Boil-Moriotte solifluction lobes, clay cryoturbation spots, poly- (pressure6volume = constant in an isothermal gonal structures, and areas of sorted ground occur environment); the accuracy is 0.02 g/cm3. between altitudes of 1000 and 1700 m. The Particle-size distribution patterns were deter- thickness of the seasonal freezing-thawing active mined for most samples by a combination of layer decreases with increasing altitude and may sieving and the pipette method after dispersion vary slightly from year to year. The maximum with sodium hexametaphosphate. seasonal melting of permafrost is up to 2.5 m at Chemical analysis was restricted to several 900 m and 50 cm at 2500 m (Abramov et al., representative samples based on their similar 2008). stratigraphical positions in comparative marker Downloaded from http://pubs.geoscienceworld.org/claymin/article-pdf/49/2/195/3301715/gsclaymin.49.2.04-kuz_OA.pdf by guest on 24 September 2021 on 24 September 2021 by guest Downloaded from http://pubs.geoscienceworld.org/claymin/article-pdf/49/2/195/3301715/gsclaymin.49.2.04-kuz_OA.pdf TABLE 1. Location, volcanic source, age and physical characteristics of the ash samples. Sample Sampling point Source Tephra Height Depth Mean age, 14C Moisture Absorbed Dry density, Solid particles no. volcano index (m) (m) years content moisture rd, density, rs 3 3 W (%) Wg (%) (g/cm ) (g/cm ) 1 0.2 1500 38 2.04 1.1 2.69 3 0.55 1500 64 4.3 0.9 2.70 Tolbachinskiy Pass À* À* 1630 5 0.75 1500 31 1.67 1.3 2.73 7 2.5 1500 30 1.24 1.5 2.80 2 Near Large Fissure 0.2 35 21 0.3 1.1 2.52 8 Tolbachik Eruption Tolbachik À* 1330 0.5 35 À* À* À* À* cones (LFTE) 4 Cones in the Kamen 0.15 ND 21 0 1.3 2.64 À* À* 1000 6 Volcano area 0.4 ND 13 0.2 1.5 2.71 9 Moraine complex of the Khangar Khg 0.36 6850 42 1.32 0.9 2.47 Bilchinok glacier, right 10 695 slope of the bold À* À* 0.56 ~7500 37 1.94 1.3 2.79 mountain 11 Moraine complex, right Sh2 0.45 950 32 0.46 1.1 2.66 12 slope of the Bilchinok Shiveluch Sh3 746 0.70 1400 36 0.81 1.1 2.61 glacier valley 13 Sh5 1.2 2550 32 1.0 1.1 2.52 14 À* À* 1.15 ~6000 34 3.94 0.9 2.79 15 Left slope of the Khangar Khg 1.32 6850 36 2.52 0.8 À Bilchinok glacier 16 À* À*290 1.5 6850À8300 42 4.14 0.9 2.1 valley, at the forest 17 boundary Shiveluch Sh8300 1.71 8300 11 1.67 1.0 2.71 18 À* À* 1.8 ~9000 69 7.3 0.8 2.46 19 Seismic station on Shiveluch Sh 2 0.65 950 32 0.3 1.0 2.68 20 Podkova, Klyuchevskoy 800 0.85 31 0.79 1.1 2.75 Klyuchevskoy À* 950À400 21 volcano slope 1.17 30 0.87 0.9 2.74 22 Shiveluch Sh2 1.1 950 43 0.32 1.5 2.58 Nappe Apakhonchich 800 23 Ksudach KS-1 2.2 1800 51 0.56 1.1 2.68 24 Kamchatka river valley, À* À* 130 5.2 Q2 À* 0.93 À* 2.45 steep bank ‘Krutoy" 1 * the specified volcanic ashes do not form key beds because they are the products of minor or remote eruptions.

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