Scientists embarked on a research expedition to the newly discovered lost continent of Zealandia. In case you hadn't previously heard, geologists found an entire continent earlier this year.
The continent of Zealandia is submerged under the sea and has been submerged for millions of years. This underwater continent, however, has a rich history of both aquatic and land-based life. For a more detailed discussion on the animals of Zealandia, check out my colleague Brid-Aine Parnell's article. With the recent scientific expedition to explore Zealandia, we have a few clues as to the history of this strange continent and how it relates to broader global plate tectonics.
You may be curious if Zealandia is underwater, why then is it a continent and not considered part of the ocean. The answer lies in the composition of the crust of Zealandia. The crust, although submerged under the sea, has the characteristics of a continental crust compared to an oceanic crust. The two different types of crust (continental and oceanic) define the shape and geography of our oceans and land.
There are major differences between the two types of crust. Density is a significant difference, oceanic crust is made up of more dense rocks than continental crust, meaning oceanic crust sits lower in the mantle as compared to continental crust. In addition, continental crust is often multiple times the thickness of oceanic crust, especially so in mountainous areas.
The continent was once above water 60-85 million years ago when it was attached to Australia. It then broke off from Australia and sank below the ocean surface. The submerged continent is roughly the same size as the Indian subcontinent, at 5 million square kilometers. Today, 95% of the continent is submerged, providing fertile ocean floor for marine life and sustaining local fisheries.
After nine weeks at sea, the team of scientists returned with sediment and rock samples from Zealandia. The research is part of the International Ocean Discovery Program (IODP), an international organization to study our world's oceans.
The sediment cores provide a record of Zealandia's history, from mountain building to land animals and shallow seas. The research team will focus on establishing the history of Zealandia through understanding its volcanism, climate, geography, and marine/terrestrial life.
The team found hundreds of fossils that range from shells to shallow marine organisms to pollen and spores from land plants.
This research will provide geologists another puzzle piece in reconstructing Earth's history. As always, a discovery of this magnitude leads to more questions than answers and this is the first step in answering some of the many questions relating to the lost continent of Zealandia.
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