On 30 June 1908 disaster struck the Earth. At 3:14 am local time the Baltic Sea, just south and east of Åland Islands.
A tsunami was caused by the impact. The angle and velocity of the impact sent a larger portion of the water east. A huge wave was funneled down the Gulf of Finland. Coastal areas along the way were devastated. Helsinki, Tallinn along with other larger settlements are devastated. Some smaller villages are completely washed away. The tsunami actually intensifies as it travels down the Gulf. It strikes St. Petersburg with overwhelming force.
The Winter Palace is devastated and the Imperial Family is killed. Other centers of governmental power for the Russian Empire are destroyed. Governmental control is decapitated.
The Åland Islands have their surface obliterated. Waves pummel Stockholm and destroy a large portion of the Swedish government.
Less devastating waves finally reach the German Empire. While no-where near as destructive as the easterly and westerly waves it is enough to destroy a portion of the German Navy and to ruin a number of ships under construction in the shipyards.
Over the next decade and beyond the Russian Empire is in chaos. Revolution and separatist groups tear at the corpse of the Empire. After the first year of rebellions growing numbers of soldiers begin to long to return home knowing that their homelands may be in danger. Mutinies strike many of the regions of the military.
The United Kingdom, Germany, and France send as much aid as possible the the Baltic region. Denmark even occupies a portion of Swedish territory to 'protect' this humanitarian aid. They never leave.
The death toll of the Baltic Event is unknown but is in the hundreds of thousands. This is followed by starvation, disease, and in Russia's case War. As mentioned these wars span over a decade and give birth to dozens of new nations. By June 1918 this is a map of the region:
The nations existing out of the former territory of the Russian Empire include:
(1) The Russian Empire (in red),
(18) Far East Federation,
(19) Free Land of Bidzhan (Manchurian enclave),
(20) Lesser Transbaikalia,
(23) Izhevsk Zavod,
Russia if focusing on re-establishing control over the Caucasus region. It is also has poor relations with Kareliya and Komi, desiring that former territory as well. As of 1918 the borders of all of these nations are still not permanent. Ethnic groups are fighting for territory, resources, ancestral lands, and strategic locations to protect their territory. It will be another generation before things begin to stabilize.
I altered history on this one by changing the timing and exact nature of what was the Tunguska Blast on the OTL. A major change to astronomical events would really have a divergence point not too long after the Big Bang. This timeline is mostly to show how devastating things could have been if such an impact hit a little off course.
I might play around a bit with this one. Perhaps a post on a Polish-Ukrainian War, maybe one on the global reaction and changes due to such a devastating event.
A number of the new countries listed above were not even established by Russia until the 1920s. Due to my own lack of time and limited knowledge of 19th century Russia I've ignored a few things. A decade of civil wars is my excuse for anything that looks out-of-place.
I hope you enjoy. Feel free to leave comments.