Which natural disaster significantly affected California in the 1970s?

The significant natural disaster that affected California in the 1970s was an earthquake, specifically the San Fernando earthquake, which occurred on February 9, 1971. This quake had a magnitude of 6.6 and struck the San Fernando Valley region, causing considerable damage and loss of life. It prompted a reevaluation of building codes and seismic preparedness throughout the state, as it uncovered vulnerabilities in infrastructure designed to withstand seismic activity.

In the context of the other options, flooding, drought, and wildfires have all impacted California at various times, but the San Fernando earthquake is particularly noteworthy for its immediate destructive power and the long-term implications it had on seismic safety measures in urban planning and construction. The 1970s in California saw significant changes in policies related to earthquake preparedness partially due to this disaster, marking its significance in the state's history.