Eruption of the Bezymianny Volcano. Bezymianny (Russian: Безымянный, meaning unnamed) is an active stratovolcano in Kamchatka, Russia. Bezymianny volcano had been considered extinct until 1955. Activity started in 1955, culminating in a dramatic eruption on 30 March 1956. This eruption, similar to that of Mount St. Helens in 1980, produced a large horseshoe-shaped crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater. The most recent eruption of lava flows occurred in February 2013. An explosive eruption on 20 December 2017 released an ash plume rising to a height of 15 kilometres (9.3 mi) above sea level, which drifted for 320 kilometres (200 mi) NE.
The modern Bezymianny volcano, much smaller than its massive neighbors Kamen and Kliuchevskoi, was formed about 4700 years ago over a late-Pleistocene lava-dome complex and an ancestral volcano that was built between about 11,000–7000 years ago. There have been three periods of intensified activity in the past 3000 years. A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. Earth’s volcanoes occur because its crust is broken into 17 major, rigid tectonic plates that float on a hotter, softer layer in its mantle. Therefore, on Earth, volcanoes are generally found where tectonic plates are diverging or converging, and most are found underwater. For example, a mid-oceanic ridge, such as the Mid-Atlantic Ridge, has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes can also form where there is stretching and thinning of the crust’s plates,
Credit: Jeff Schmaltz