Shiveluch was the first to explode, sending ash high above the Kamchatka Peninsula at midday on October 6.
Satellite observations revealed that the plume blew southeastward for about 50 miles before being directed eastward over the open waters of the Bering Sea by a shift in the prevailing winds.
Since the ash reached heights of less than 10,000 feet, it was not considered a threat to aircraft flying through the main aviation routes between North America and Asia.
Klyuchevskoy began to erupt nine days later with glows at night that indicated to observers that lava was flowing down its slopes.
The last eruption of Klyuchevskoy took place from September 2009 to December 2010.
It is considered sacred by some indigenous peoples, being viewed by them as the location at which the world was created.