Tonga lies west of the Tongan Trench, on the Indo-Australian plate. The lowest point in Tonga is the Pacific Ocean at 0 m. The highest point is an unnamed location on Kao Island 1,033 m above seal level. Most islands are made from limestone (uplifted coral) at their base or with a limestone layer atop volcanic features. Read more →
Some islands have tall cliffs on one side of their coasts due to volcanic uplift (such as Eua), with coral gardens and sandy beaches on their opposite coast.
Many islands in Tonga are coral cays. They exist in tropical environments throughout the main oceans of the world. They forms when currents dump sediment on the surface of a reef. Over time, the sediment builds up until it is entirely above sea level. They are flat islands with beautiful coral sand beaches.