Caldera Ksudach (Kamchatka): modern processes of relief forming and main features of the valley network structure
Ksudach volcano (Kamchatka) consists of 5 completely or partially nested calderas Late Pleistocene (calderas I and II) and Holocene (III–V) age. Analysis of the processes of relief forming and structure of intracaldera river valleys leads to the conclusion that, despite the high Holocene volcanic activity of Ksudach (volcano-tectonic collapse, significant amounts of ejected pyroclastic material) the upper reaches of many of modern valleys were formed on the slopes of calderas I and II. And nowadays they are still function as the upper parts of the younger Holocene valleys of calderas IV and V. These fragments of upper parts of the Late Pleistocene river network surviving after Holocene caldera forming explosions continued to concentrate runoff and as a result the lower parts of the river network, destroyed during eruptions, begun to restore, but depending on the newly formed volcanic relief. The growth of the Shtyubel cone within the caldera V also had a significant influence on the orientation and morphology of adjacent valleys: in particular, it has led to Lagernyi creek alteration, which made a turn for 120during the Late Holocene. The fragment of its ancient valley preserved in the form of a flat-bottomed saddle on the WSW of the vlc. Shtyubel and now it’s gradually degraded by erosion. Explosive activity of Ksudach vlc. (including Shtyubel cone) had great influence on the intracaldera river systems: powerful pyroclastic flows repeatedly filled up their valleys and came down along the river Teplaya. Subsequent incision of valleys led to the formation in them of erosion terraces composed by pyroclastic deposits.
Keywords: долинная сеть, перестройка, геоморфологические процессы, вулкани- ческий рельеф, пирокластические отложения.