Tolbchik Volcano isn't a single peak, but a complex of volcanic features superimposed on one another. The varied shapes result from differences in lava chemistry, gas content and temperature.
Over time the composition of magma feeding a volcano may change, generating volcanoes with complex shapes. Tolbchik's most recent eruption, which started in late 2012, is on Tolbachinsky Dol, a lava plateau marked by small volcanic cones that formed during earlier eruptions.
These cones stretch southwest from the summit of Plosky Tolbachick, a gently sloping shield volcano formed from layers of fluid lavas. Just to the west of Plosky Tolbachik lies Ostry Tolbachik, a steep-sided stratovolcano composed of layers of thick lava, ash, tephra and other volcanic debris.
Image courtesy of NASA.