Microcontinent

Microcontinent is a fragment of continental crust that is smaller than a continent, typically separated from larger landmasses by oceanic crust. Such fragments usually retain continental-type crust with granitic composition, relatively thick crust, and old ages, often dating back more than a billion years. They differ from true oceanic crust in their geochemical signatures and seismic properties.

Origin and fate: Microcontinents form during the breakup of larger landmasses in global supercontinent cycles, such as Rodinia and Gondwana. Rifting can detach pieces of crust that then drift on the mantle and may be carried by plate tectonics for tens or hundreds of millions of years. They may collide with other plates, be accreted to larger continents, or remain as isolated blocks; some regions are now submerged beneath ocean basins.

Examples: Zealandia, a largely submerged continental fragment in the southwest Pacific that includes New Zealand and New Caledonia, is a widely cited example. Madagascar is often described as a microcontinent that separated from Africa during Gondwana's breakup. Other proposed remnants include buried crust in the Indian Ocean region such as Mauritia; however, the designation of Mauritia is debated.

Terminology and significance: The label microcontinent is not universally formal but is commonly used to distinguish small continental fragments from oceanic crust. Studying microcontinents aids paleogeographic reconstructions of past supercontinents and clarifies processes of crust formation, breakup, and continental stability.