According to le chatelier's principle, what would happen if the equilibrium of a weack acid or weak base were upset

The conc. of products shall increase to nullify the effect of change in concentration. For this purpose, equilibrium would shift to right. 

Reason:

According to  Le Chatelier's principle: "If a chemical system at equilibrium experiences a change in concentration, temperature, volume, or partial pressure, then the equilibrium shifts to counteract the imposed change and a new equilibrium is established."

So, more reactant (weak acid or weak base) would result in shift of equilibrium towards right (i.e. toward products). Hence, the conc. of products would increase so that new equilibrium could be established.

They did not study the continental drift