What caused the energy crisis of 1973?

It was that OPEC organized a stop to fuel exports in the hopes of raising prices that caused the Energy Crisis of 1973, which led many nations to seek alternative fuels. 

Oil crisis. The 1973 oil crisis began in October 1973 when the members of the Organization of Arab Petroleum Exporting Countries proclaimed an oil embargo.

Because the discoveries were some of the oldest human remains.