10 Causes of Major Stock Market Crashes

10 causes of major stock market crashes:

• political events 
• government actions
• war, terrorist attack
• currency crisis
• credit crisis
• debt defaults
• bank failures
• commodity price crisis
• stock crashes in a major market becomes contagious
• technical (flash crashes)

Many of these events cannot be predicted. These events can happen anywhere in the world. Global markets are now highly correlated. Thus, to avoid these black swans with certainty, you'd have to be out of the market most of the time. 

Hence, an investor should stay invested and the safest way to invest is by value investing.