They are unexpected but happen regularly enough in a general population to be broadly predictable, and may be the subject of casualty insurance.
Good examples of external risks are natural disasters such as earthquakes and volcanoes.
As far as claims go, most external risks, or an "Act of God", are protected by property insurance.
Good examples of external risks are changes in government legislation, changes in strategy from senior managers, and the economy.
Three separate aspects should be analyzed when determining the amount of external risk that exists.