Ksudach

In the left foreground of the Ksudatsch (Recording from the east from the Space Shuttle )

Location of the calderas of Ksudatschbdep2

The Ksudatsch (Russian Ксудач ) is a stratovolcano in the south of the Kamchatka Peninsula. Five nested calderas dominate the summit of the volcano, which is the Kamchatka region in Russia in Rajon Yelizovo.

Location

The Ksudatsch is part of Ostkette Kamchatka, a volcanic zone of about 700 kilometers in length and 80 kilometers in width, in which nearly all the active volcanoes of the peninsula are located. Cause of volcanism is a subduction zone, where the Pacific plate dives under the Eurasian plate. The volcano is located about 150 km south-southwest of Petropavlovsk -Kamchatsky, the capital of Kamchatka.

Construction and outbreaks

The first volcanic eruptions of Ksudatsch took place around 40,000 years ago. Outbreaks, which predominantly andesite was encouraged, came from several eruption centers. There was a flat as a " shield -like" described volcanic edifices, which is composed of lava and tephra. Two outbreaks in the late Pleistocene left the summit area of the volcano to collapse, with the calderas I and II were formed. The former has a diameter of 10 to 11 kilometers. Little is known about these two eruptions since the glaciation of Ksudatsch in the subsequent cold period destroyed the associated ash deposits.

In the Holocene calderas III, IV and V arose within the two older calderas:

• The Caldera III was formed during an eruption around 7900 BC, in which ³ tephra was promoted between 1.5 and 2 km. The size of the caldera is estimated at 2 to 3 kilometers. The outbreak of the strength on the five Vulkanexplosivitätsindex ( VEI ) was preceded by at least 1000 -year-long period in which there were no or only weak eruptions.
• Two consecutive short bursts around 5200 and 4900 BC created the caldera IV with a size of 5 to 6 km. Both eruptions had a VEI strength of five; There were funded a total of 10 to 11 km ³ of tephra. After the collapse of the caldera lava domes created from several dacite.
• The caldera was formed in an eruption V to 240 AD, which is compared with the eruption of Krakatoa in 1883. The eruption with a VEI strength of six began with minor phreatomagmatic explosions. Plinian eruptions followed, in which a rise an estimated 30 to 36 mile-high eruption column and approximately 15 km ³ of tephra were promoted. At the same time pyroclastic flows moving up to 20 kilometers away from the crater; their deposits are estimated at 3 to 4 km ³. In the second half of the eruption, the 4 kilometer caldera formed at 6.5 V with a volume of 6.5 and 7 km ³. The ashes of the eruption was distributed mainly to the north and is still in 1000 kilometers detectable. In Kamchatka the eruption had significant ecological consequences: Covering an area of 12,000 sq km, the vegetation was damaged; at least 400 square kilometers were completely devastated.

In contrast to the previous calderabildenden eruptions of Ksudatsch, which was followed by long periods of rest or only minor outbreaks, it came about 100 years after the formation of the caldera V to further outbreaks: Lava flows and moderate explosive eruptions built in the north of the caldera, the volcano V Stübel ( вулкан Штюбеля, also Stubel and Shtyubel ') on. The after the German naturalist and volcanologists Alphons Stübel Moritz (1835-1904) named volcano was about the year 1000 and 1750 starting point for two outbreaks of VEI strength of four, where pyroclastic flows or mud flows, lahars called arisen.

The only outbreak of Ksudatsch in historical time took place in March, 1907. Here, in the sparsely populated Kamchatka nature and exact location of the eruption remained unknown until 1910, an expedition went to the volcano. At the beginning of the eruption destroyed two smaller, possibly phreatic explosions partly a lava dome that formed the summit of Strübels. This paved the way to the surface was free for the magma. The pressure relief triggered a sustained Plinian eruption probably several hours, when an eruption column rose at least 22 miles high. Ash fall was registered in 1000 yet miles away. After a short rest period, there was a predominantly horizontal directional explosion that was probably caused by the access of water to the conveyor system of the volcano. The explosion destroyed the north- northeastern part of the Strübels, whereby water came to the magma from an existing crater lake in contact. This triggered a series of hydro- magmatic explosions, with up to 15 km far-reaching pyroclastic surges formed. With the eruption of VEI strength five around 2.4 km ³ of tephra were promoted.

The eruptions of the Holocene Ksudatsch Basaltandesit and rhyodacite was promoted. The deposited tephra contains many units of mafic and felsic pumice alike, suggesting an intense mixture of molten rock during eruptions.

Presence

The highest point of Ksudatsch with 1079 meters is located on the southern edge of the caldera I. In enclosed by steep walls caldera two lakes have formed with a water level of 415 meters above the sea, the Kljutschewoje Lake ( oзеро Ключевое ) in the south and the Stübel Lake ( oзеро Штюбеля ) in the north. A bay of Lake Stübel fills the horseshoe-shaped, open to the north- north-east crater of the volcano Stübel; the lake to reach a depth of 300 meters in the crater area. The partially classified as tuff, partly as a cinder cone Stübel reaches a height of 630 meters above sea level; at the outbreak of 1907, the top 100 to 200 meters of the cone were destroyed. On the shores of Lake Kljutschewoje There are several thermal sources; in the area of ​​Stübel crater rise to gases.

Even in the presence of the area around the Ksudatsch is barely tapped. For tourist helicopter flights to Caldera offered. In addition, the Ksudatsch can be achieved in days spent by Kurilensee (50 kilometers south-west ) and from the volcanoes Mutnovsky and Gorely (around 90 kilometers north-east ). For the monitoring of the volcano, the Kamchatka Volcanic Eruption Response Team ( KVERT ), an agency of the Russian Academy of Sciences, in charge. Among the possible dangers that could be caused by an outbreak of Ksudatsch, ash fall in Petropavlovsk -Kamchatsky and in the 80 km south-west to settlement Osernowski be counted. In addition, could form lahars, especially in the valley of the river Tjoplaja ( Tёплая ), which drains the caldera to the north.