A string of more than 170 tremors were detected within the volcano over a 24-hour period ending late Sunday.
The 10,771-foot volcano erupted in December 2006 and has remained activity ever since, according to regional scientific monitor on the Kamchatka Peninsula.
Yury Demyanchuk, head of the Klyuchevskaya seismological volcano monitoring station, told RIA Novosti that the activity since Shiveluch’s 2006 awakening has altered the contour of the volcano.
The crater has increased in size by 50 percent and the slopes have become much steeper.
There are more than 150 volcanoes on Kamchatka, 29 of them active. Shiveluch is the northernmost volcano on the peninsula.
Its last significant activity was in late April when the mountain shot ash more than 9,000 feet into the sky.
It is part of the Kiyuchevskaya volcano group and estimated to be about 65,000 years old. Catastrophic eruptions in 1854 and 1956 caused a large part of its lava dome to collapse.
Photo: Yuri Demyanchuk
Kamchatkan Branch of (Russian) Geophysical Surveys