Which type of slide can occur suddenly?

A landslide, specifically a rock or debris slide, can occur suddenly due to various triggering factors such as heavy rainfall, rapid snowmelt, earthquakes, or human activities that destabilize slopes. These slides are characterized by the rapid movement of rock or soil down a slope, resulting in a dramatic loss of stability. The sudden occurrence is what distinguishes this type of slide from others that may develop more slowly over time.

In contrast, a slump often involves a rotating movement of earth material and occurs more gradually. Creep involves the slow, continuous movement of soil and rock, which is almost imperceptible on a day-to-day basis. Soil flow, while it can be somewhat rapid, typically moves materials in a more fluid manner and may not have the abruptness associated with landslides. Hence, the sudden nature of a landslide aligns with the characteristics of the correct option.