This fall is linked to the new, more severe sanctions imposed on Moscow by the international powers.
The ruble collapsed against the dollar and the euro on the Moscow Stock Exchange on Monday morning, and trading came to a halt as prices almost instantly reached the limits set.
You had to provide 90 rubles to get a dollar on Monday morning, against 83.5 at the last official rate on Wednesday, before the invasion of Ukraine. Against the euro, the exchange rate fell from 93.5 to 101.19 rubles.