section_path: Geography/Geology
section_name: Geology
paragraph_text: Geology
  
  The Pacific Plate, which makes up most of Oceania, is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres (40,000,000 sq mi), it is the largest tectonic plate. The plate contains an interior hot spot forming the Hawaiian Islands. It is almost entirely oceanic crust. The oldest member disappearing by way of the plate tectonics cycle is early- Cretaceous (145 to 137 million years ago).
  
  Australia became part of the Indo-Australian plate 45 to 40 million years ago and this is in the process of separating again with the Australian Plate being relevant to Oceania. It is the lowest, flattest, and oldest landmass on Earth and it has had a relatively stable geological history. Geological forces such as tectonic uplift of mountain ranges or clashes between tectonic plates occurred mainly in Australia's early history, when it was still a part of Gondwana. Australia is situated in the middle of the tectonic plate, has occasional middle-sized earthquakes, and currently has no active volcanism (but some volcanoes in southeast Australia erupted within the last 10,000 years).
  
  The geology of New Zealand is noted for its volcanic activity, earthquakes, and geothermal areas because of its position on the boundary of the Australian Plate and Pacific Plates. Much of the basement rock of New Zealand was once part of the super-continent of Gondwana, along with South America, Africa, Madagascar, India, Antarctica and Australia. The rocks that now form the continent of Zealandia were nestled between Eastern Australia and Western Antarctica.
  
  The Australia-New Zealand continental fragment of Gondwana split from the rest of Gondwana in the late Cretaceous time (95–90 Ma). By 75 Ma, Zealandia was essentially separate from Australia and Antarctica, although only shallow seas might have separated Zealandia and Australia in the north. The Tasman Sea, and part of Zealandia then locked together with Australia to form the Australian Plate (40 Ma), and a new plate boundary was created between the Australian Plate and Pacific Plate.
  
  Most islands in the Pacific are high islands (volcanic islands), such as, Easter Island, American Samoa and Fiji, among others, having peaks up to 1300 m rising abruptly from the shore. The Northwestern Hawaiian Islands were formed c. 7 to 30 million years ago, as shield volcanoes over the same volcanic hotspot that formed the Emperor Seamounts to the north and the Main Hawaiian Islands to the south. Hawaii's tallest mountain Mauna Kea is 4,205 m (13,796 ft) above mean sea level.