Abstract
The study of moraines at the Avacha volcano group revealed that glaciers changes at all volcanoes within the group happened almost synchronously. Glacial deposits could be grouped into three generations, corresponding to three periods of glacier fluctuations in Neoholocene. The largest glaciation within the group occurred ~2000 years ago. Fragments of moraine, corresponding to that period were found only in the moraine complex of the Ditmar Glacier which was 15% larger then today at that time. The most of moraines at the Avacha volcano group were formed during the Little Ice Age, which in the studied region continued up to the first decades of XX centuries. The maximal advance of glaciers probably happened in XVII century. The moraine corresponding to that period was found at the Kozelsky Glacier valley. At present time the total area of glaciers which moraines were described and dated approaches 21.46 km2. The area of reconstructed moraines corresponding to the Little Ice Age is estimated to be 2.79 km2, therefore at that period the total glaciation area reaches 24,25 км2 exceeding the present area by 13%. It could be claimed that in general during the time past the Little Ice Age the glaciation nature and glacier types did not change sufficiently. The rate of glacier degradation at various parts of the group is different and depends mainly on exposition. At the valleys of four glaciers we found moraines formed in the middle of XX century. They may appear in 1941–1952 when the unfavorable weather conditions leaded to stable negative anomalies in accumulation have happened.
Highlights
Представлена реконструкция колебаний ледников Авачинской группы вулканов в позднем голоцене по результатам изучения моренных комплексов
At the valleys of four glaciers we found moraines formed in the middle of XX century
Рых лые, часто пористые и почти лишённые глинистых частиц отложения пирокластики легко размыва ются и уносятся водными потоками
Summary
Представлена реконструкция колебаний ледников Авачинской группы вулканов в позднем голоцене по результатам изучения моренных комплексов. Авачинская группа вулканов – второй по ве личине центр оледенения на Камчатке среди рай онов активного вулканизма [1]. Виноградов с соавторами [9] дают оценку площади ледников Авачинской группы вулканов в середине XIX в., но с уточнением, что эта оцен ка не отличается большой точностью, так как большая часть подсчётов выполнялась путём де шифрирования аэрофотоснимков, при котором не учитывались некоторые участки морен, раз мытые талыми водами. Резуль татом работы было определение скорости роста лишайников Rhizocarpon geographicum в специфи ческих условиях Камчатки и подробное описание моренных комплексов ледников разных районов полуострова с датировками, в том числе и для пяти ледников Авачинского узла оледенения [4]. Цель настоящей работы – оценить масштаб оледенения вулканов Авачинской группы в позднем голоцене.
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