From Douwe van der Meer
In his time traveller’s guide to Earth, imagining 250 million years ago, Joshua Howego wrote: “From the other side of the planet all you see is an unbroken expanse of ocean, Panthalassa” (18 July, p 28). Although Panthalassa is generally illustrated as an uninterrupted vast blue ocean, this is because of a lack of data.
Recent research has shown that volcanic arcs and small continents were present and would have interrupted the unbroken expanse. These have ended up in north-eastern Asia and western North America, where their remains are outcropping today. Subducted fragments of them are detected in the mantle beneath the Pacific. There is more detail in a 2012 paper I co-authored in Nature Geoscience ().
Ruislip, Middlesex, UK
