PERTH, Australia – Scientists have discovered two huge sunken islands in the Indian Ocean, west of Australia.
The islands -- about the size of West Virginia or Scotland -- were once part of the supercontinent Gondwana and are almost a mile (1.6km) underwater.
Researchers from the University of Sydney, Macquarie University and the University of Tasmania said the islands were once above water and formed part of the last link between India and Australia.
The scientists made the discovery while mapping the seafloor of the Perth Abyssal Plain.
"The data collected on the voyage could significantly change our understanding of the way in which India, Australia and Antarctica broke off from Gondwana," University of Sydney geologist Dr. Joanne Whittaker said.
The islands, called "micro-continents," were formed when India began to move away from Australia, about 130 million years ago during the Cretaceous period, when dinosaurs roamed the Earth.
They became stranded thousands of miles (kilometers) from either coast as the land masses separated.
"The sunken islands charted during the expedition have flat tops, which indicates they were once at sea level before being gradually submerged," Whittaker said.
In paleogeography, Gondwana, originally Gondwanaland, was the southernmost of two supercontinents (the other being Laurasia) that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago (Mya). Gondwana is believed to have sutured between ca. 570 and 510 Mya, thus joining East Gondwana to West Gondwana. It separated from Laurasia 200-180 Mya (the mid Mesozoic era) during the breakup of Pangaea, drifting further south after the split.
Gondwana included most of the landmasses in today's Southern Hemisphere, including Antarctica, South America, Africa, Madagascar and the Australian continent, as well as the Arabian Peninsula and the Indian subcontinent, which have now moved entirely into the Northern Hemisphere.
The continent of Gondwana was named by Austrian scientist, Eduard Suess, after the Gondwana region of central northern India (from Sanskrit gondavana "forest of the Gonds"), from which the Gondwana sedimentary sequences (Permian-Triassic) are also described.
The adjective Gondwanan is in common use in biogeography when referring to patterns of distribution of living organisms, typically when the organisms are restricted to two or more of the now-discontinuous regions that were once part of Gondwana, including the Antarctic flora. For example, the Proteaceae, a family of plants known only from southern South America, South Africa and Australia, are considered to have a "Gondwanan distribution". This pattern is often considered to indicate an archaic, or relict, lineage.