Mariana Trench: new tectonic plate and surprising deep sea volcano?

Mariana Trench record deep tectonic plate volcano rocksNot just perhaps a new tectonic plate discovered deep in the Mariana Trench but also surprisingly deep volcanic activity at over 3 miles deep with volcanic glass evidence.

New deep undersea tectonic plate discovered?

... a sample collected from an earlier expedition suggested that a previously undiscovered tectonic plate lies at the bottom of the trench.
Mariana Trench deep sea volcano discovered"The rock we picked up - it turns out this thing is 100 million years younger than the Pacific Plate," she told BBC News.
"It means that the plate that's being subducted beneath the Challenger Deep (the lowest point of the trench) is 100 million years or more younger than the Pacific Plate."
New record for deepest fish

New deep undersea volcano activity where there should be none?

mariana-trench-deep-sea-volcano-discovered

At the plate boundary, the scientists also found rocks that suggested volcanic activity at a depth of 5,000m - the deepest underwater eruption known.
"The amazing thing about these little rocks is that they are all covered with volcanic glass," Prof Fryer explained.
"The only way they form is if this volcanic magma is instantly cooled when it left the vent - material coming out hit the sea water and instantaneously froze.
"Most volcanologists would say that you can't get explosive volcanism much deeper than a couple of km - but we found these rocks 5,000m down."
New record for deepest fish

Could the rocks and 'volcanic glass' have been formed through a different process?

Is it the discovery of a new tectonic plate deep below the sea or could the rocks dating have been changed by natural processes?

Why is geology always surprised by what it finds that it can and did not predict?