How does ignorance occur?  

Ignorance occurs by ignoring – thus the more you ignore something the more ignorant you become.  But, ignorance is a part of a cycle of Creator, Preserver, and Dissolver.  Ignorance is an attribute of the dissolver which means the birth of awareness dawns after ignorance.  If you choose to ignore something long enough the universal school of LIFE provides us with different experiences offering varying perspectives albeit the same lesson with clues to remember who we are rather than continuing down the path of ignorance.  However, sometimes unconsciousness must be met with severity and adversity to WAKE us UP to embark on the journey of self-reflection, the Inner Quest, the Immortal Quest, The Real IQ, to see ourselves.  Ancient Kamitan (Egyptian) Proverb – “… Adversity is the seed of well-doing…”