It could also be a major announcement from Russia or China that they are no longer going to conduct any business in US dollars.
I am also feeling China and Russia make a new joint currency backed by gold, instantly sinking the dollar, at that point.. .. boom.
And I really don't know why people keep using the word "Russia" as if it has any economic significance! Russia's GDP was less that Italy last time I looked!
If the conflict in Russia/Ukraine were to escalate further then there could be economic issues.