desertification is a mean of comets pile
desertification is not destruction_event. desertification is not creation_event. desertification is creation_event. desertification is physical_destruction_event. desertification is physical_creation_event. desertification is not physical_creation_event. desertification is geological_process. desertification is not geological_process. desertification is not physical_destruction_event. desertification is destruction_event.