<P> Nevertheless, the oldest cratons on Earth include the Kaapvaal craton, the Western Gneiss Terrane of the Yilgarn craton (~ 2.9--> 3.2 Ga), the Pilbara Craton (~ 3.4 Ga), and portions of the Canadian Shield (~ 2.4--> 3.6 Ga). Parts of the poorly studied Dharwar craton in India are greater than 3.0 Ga . The oldest dated rocks of the Baltic Shield are 3.5 Ga old . </P> <P> The Acasta Gneiss in the Canadian Shield in the Northwest Territories, Canada is composed of the Archaean igneous and gneissic cores of ancient mountain chains that have been exposed in a glacial peneplain . Analyses of zircons from a felsic orthogneiss with presumed granitic protolith returned an age of 4.031 ± 0.003 Ga . </P> <P> On September 25, 2008, researchers from McGill University, Carnegie Institution for Science and UQAM announced that a rock formation, the Nuvvuagittuq greenstone belt, exposed on the eastern shore of Hudson Bay in northern Quebec had a Sm - Nd model age for extraction from the mantle of 4.28 billion years . However, it is argued that the actual age of formation of this rock, as opposed to the extraction of its magma from the mantle, is likely closer to 3.8 billion years, according to Simon Wilde of the Institute for Geoscience Research in Australia . </P> <P> The zircons from the Western Australian Jack Hills returned an age of 4.404 billion years, interpreted to be the age of crystallization . These zircons also show another interesting feature; their oxygen isotopic composition has been interpreted to indicate that more than 4.4 billion years ago there was already water on the surface of the Earth . The importance and accuracy of these interpretations is currently the subject of scientific debate . It may be that the oxygen isotopes and other compositional features (the rare - earth elements) record more recent hydrothermal alteration of the zircons rather than the composition of the magma at the time of their original crystallization . In a paper published in the journal Earth and Planetary Science Letters, a team of scientists suggest that rocky continents and liquid water existed at least 4.3 billion years ago and were subjected to heavy weathering by an acrid climate . Using an ion microprobe to analyze isotope ratios of the element lithium in zircons from the Jack Hills in Western Australia, and comparing these chemical fingerprints to lithium compositions in zircons from continental crust and primitive rocks similar to the Earth's mantle, they found evidence that the young planet already had the beginnings of continents, relatively cool temperatures and liquid water by the time the Australian zircons formed . </P>

Where is the oldest known rock on earth located