What type of hazards are classified as sudden phenomena?

Sudden phenomena are events that occur rapidly and often without significant warning, leading to immediate and sometimes devastating impacts. Earthquakes fall into this category because they can happen unexpectedly and are typically characterized by their abrupt onset. They can cause serious damage to structures, trigger landslides, and result in injuries or fatalities due to their unpredictable nature.

In contrast, other hazards such as soil erosion events and droughts develop over time and can be monitored or anticipated, making them less sudden in comparison. Floods and landslides can involve both sudden and gradual phases, but earthquakes are solely defined by their instant and explosive occurrence. Therefore, earthquakes serve as the clearest example of a sudden phenomenon among the provided options.