Tongan authorities have lifted a tsunami alert triggered by a magnitude-6.6 earthquake on Monday. The United States Geological Survey (USGS) said the earthquake struck about 200 kilometres north of the main island of Nuku’alofa at a depth of 112 kilometres. Tonga Meteorological Services issued a tsunami alert for the Pacific Island nation following the quake, which it said had a magnitude of 6.9. It urged residents to move immediately to higher ground or inland. The service lifted the alert after about an hour but said “small unusual waves, currents and abnormal tides,” may still affect Tongan…