A very interesting story is on the BBC web-site:
Sea floor records ancient Earth. I love the para: “You can actually recognise features that formed in a couple of minutes, 3.8 billion years ago – a quarter of all time – and you can actually go and touch them with your hand,” said Professor Rosing.
Imagine that, touching something that is 3.8 billion years old! Of course, we are all made of atoms many of which resulted from a supernova about 4.55 billion years ago, not to mention matter that appeared about 13 billion years ago. All of us, 13 billion years old! Extraordinary!
The ancient sea floor was discovered in southwest Greenland
A sliver of four-billion-year-old sea floor has offered a glimpse into the inner workings of an adolescent Earth.The baked and twisted rocks, now part of Greenland, show the earliest evidence of plate tectonics, colossal movements of the planet’s outer shell.
Until now, researchers were unable to say when the process, which explains how oceans and continents form, began.
The unique find, described in the journal Science, shows the movements started soon after the planet formed.
The rocks analysed in Greenland are found in an area known as the Isua Belt, a zone of intensely deformed rocks in the southwest of the island that geologists have pored over for decades.
The ophiolite structure was mapped between outcrops covering 4-5km (2.5-3 miles) and shows the correct sequence of layers found in an ophiolite, except the lowest mantle portion.
“You can actually recognise features that formed in a couple of minutes, 3.8 billion years ago – a quarter of all time – and you can actually go and touch them with your hand,” said Professor Rosing.
Crucially, they show well preserved sheeted dykes and pillow lavas, clear evidence to many that these are the ancient remains of sea floor created by processes seen today.
“What this tells you unequivocally is that the process of sea-floor spreading that we observe today appears to be present in one of, if not the, oldest sequence of rocks on Earth,” said Professor Moores. “That is a significant milestone.”
“These fragments are extremely rare,” said Professor Rosing. “It’s just very exciting when you get one of these glimpses when you can look back nearly four billion years in time.”