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Zealandia
Aug 01, 2017

[GS Paper I: (Salient features of world’s physical geography)]

Why in news?

  • Recently, scientists have found that ‘Zealandia’ is a unified landmass and should be considered as a separate continent. 
  • On July 27 thirty scientists from the International Ocean Discovery Program (IODP) set out from Australia for an expedition to drill into the seafloor to understand the history and structure of Zealandia.
  • This team of international scientists will drill about 1,000 to 2,600 feet into the seafloor at six sites in the Tasman Sea to collect sediment samples – containing fossil evidence - deposited over millions of years.

Significance of the expedition

  • This expedition will help to understand the process of tectonic plate subduction.
  • It will also provide an understanding on relationship between tectonic shifts and climate change.
  • The study of recovered cores will give insights on oceanographic history, sub-seafloor life and earthquake generating zones.
  • Scientists may also be able to link the changes in the global tectonic configuration that started about 53 million years ago with Pacific “Ring of Fire”, a hotspot for volcanoes and earthquakes, which came into existence around the same time.

What is Zealandia?

  • Zealandia which is also known as New Zealand continent or Tasmantis is a mass of continental crust, most of which is submerged beneath the southwest Pacific Ocean. 
  • It covers around 4.9 million square kilometers region of the southwest Pacific Ocean, 94% of which is submerged. It is almost two-thirds the size of Australia.
  • The areas that are not submerged include New Zealand, New Caledonia, Norfolk Island and Lord Howe Island group.

Four attributes of a continent
1. Elevation with respect to the oceanic crust: Continents and their continental shelves vary in height but are always elevated relative to oceanic crust. Zealandia is everywhere substantially elevated above the surrounding oceanic crust.
2. Diverse geology: Continents have diverse assemblages of rocks such as granite, limestone, quartzite, schist, gneiss etc. Zealandia has a drape of at least two dozen spatially separate sedimentary basins. 
3. Continental crust variation with respect to the oceanic crust: Continental crust varies considerably in thickness and physical properties. Zealandia has a continued continental crust velocity structure and a thickness typically ranging from 10 to 30 km, thicker than about 7-km-thick crust of the ocean basins.
4. Continent- ocean boundaries: Various kinds of continent-ocean boundaries (COBs) define natural edges to continents. Zealandia is bounded by well-defined geologic and geographic limits. 

Background

  • In 1995, American geophysicist Bruce Luyendyk used the name Zealandia to describe New Zealand, the Chatham Rise, Campbell Plateau and Lord Howe Rise.
  • It separated from Gondwana supercontinent about 75 million years ago.
  • Earlier, it was thought to be a micro-continent or a collection of continental fragments possessing three out of four key criteria essential for landmass to be called a ‘continent’.

PT facts

  • IODP is an international marine research collaboration, which began in 2013. It builds on the research of four previous scientific ocean drilling programs: Project Mohole, Deep Sea Drilling Project, Ocean Drilling Program, and Integrated Ocean Drilling Program. Together, these programs represent the longest running and most successful international Earth science collaboration. 
  • India’s Ministry of Earth Sciences is one of the five additional funding partner agencies of IODP. 
  • Plate tectonics theory deals with the dynamics of Earth’s outer shell, the lithosphere. It provides a uniform context for understanding mountain-building processes, volcanoes, and earthquakes.
  • Ring of Fire, also called Circum-Pacific Belt or Pacific Ring of Fire, is a long horseshoe-shaped seismically active belt of earthquake epicenters, volcanoes, and tectonic plate boundaries that borders the Pacific basin. Majority of the world’s strongest earthquakes and approximately 75 % of the world’s volcanoes occur within the Ring of Fire.


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