Which one of the following describes a characteristic of fast land changes?

Fast land changes are characterized by their rapid and often unexpected occurrence, which aligns with the choice that states they happen quickly and unpredictably. This can include events such as landslides, volcanic eruptions, or earthquakes, which can dramatically alter the landscape in a relatively short amount of time. Understanding this characteristic is crucial in studying geological processes and their impacts on the environment and human activities.

In contrast, the other options suggest qualities that do not accurately describe fast land changes. For instance, changes that occur over a long period of time are typically associated with gradual processes like erosion or sediment deposition. Similarly, gradual and unnoticeable changes refer to subtle transformations that take place over extended periods, contrasting with the abrupt nature of fast land changes. Lastly, the notion of planned and organized changes implies human intervention and intentionality, which does not apply to natural geological processes that happen swiftly and often without warning.