has come from GPS technology where we can actually porta transmitter I'll and then come back here after year and actually follow it moving a few centimeters a year towards the tranny the needs devouring the crust at a rate of three inches a year and about as fast as a human finger nail rooms Juan every four million years it swallows an area the size of the United States the my consuming the crust created the Pacific Ocean Ridge the ravenous Marianas Trench is the world's largest recycling plant bon I'm but there was one remaining and major piece in the puzzle to find scientists still didn't know why it is the deepest wrench on earth one they suspected the age of the sea floor at the bottom of the trench may provide the answer it turns out there's a really strong relationship between the age the seafloor and its steps in the water the in 1999 the team the deep sea drilling is returned to the trench to collect core samples well one great thing about drilling session crosses we actually got pieces of it self we're holding our hands here material that that actually get a subducted Marianas Trench and it turned out to be a 170 million years old so we can say with confidence that the oldest ocean floor before it's getting swallowed up in the mantle
at the trench but why is this piece a rock the oldest on the ocean floor vissi for the Marianas Trench is so old because it's been so long since it was born so it was born in pick one up the eastern Pacific today and it's just me been going on longer than than any other place in the oceans sportsman's K E the Pacific plate is the planet's largest tectonic plate covering an area 11 times the size of the United States any ruled when crushed bubbled up at the ridge $170 million years ago it was light and buoyant but as a travel 10,000 miles across the plate it cooled and became compact and dense over millions have years the dense crust got heavier and began to sink into the mantle below the on scientists realized that because the cross that the Marianas Trench is the oldest ocean crust it's also the heaviest and so has sunk deeper into the mantle than any other area ocean crust ok here at last was the explanation for the trenches extraordinary depth of the picture the Marianas Trench is almost complete the volcanic islands mirroring the trenches exact shape lead scientist to believe it runs along a subduction zone and slippery mud volcanoes explain why it doesn't create large earthquakes but one question remains: unanswered towards the trenches southern the vast chasm drops a further two miles to its lowest point the Challenger Deep seven miles beneath the waves on the question is what makes it plunged so deep line the investigation into the Marianas Trench has one final puzzle to solve on at the trenches southern end the seafloor plummets a further 10,000 feet you into a