The term for a sudden geological change in an active region is known as earthquake. Earthquakes occur when there is a sudden release of energy in the Earth's crust, typically due to the movement of tectonic plates along fault lines. This release creates seismic waves that can result in significant ground shaking and may cause damage to structures, trigger landslides, or even tsunamis. Understanding earthquakes is essential for disaster preparedness and minimizing risks to life and property in seismically active areas.