Likewise, if the theory of sea-floor spreading is correct, then at any point on the sea floor the fossils found by drilling down to the bottom of the sea-floor sediment will be those deposited when that bit of the sea-floor was freshly produced at the rift.
This means that if we look at these deepest-buried fossils, we will see older and older fossils as we look further and further from the ridge; as a result we will see a greater proportion of extinct species. Different sediments tend to accumulate on different parts of the ocean floor.
If the ocean floor stayed still, then, other things being equal, we would expect a sample of the sediment from any particular place on the sea floor to be pretty much the same all the way down.
But according to the theory of sea-floor spreading, the sea-floor has been continuously moving outward from the ridge systems like a conveyor belt, which implies that different sediments will have settled over the same portion of sea-floor as it moved.
The proposition that the sea floor spreads out from the mid-ocean rifts, and has been doing so for millions of years, implies a diverse assortment of testable predictions, all of which turn out to be true.
As we discussed in a previous article, the Earth's magnetic poles keep swapping their positions. If igneous rocks have been formed at and spreading out from the mid-ocean rifts, then when we look at the paleomagnetic record in the igneous rocks that form the oceanic crust, what we ought to see is a pattern of stripes of alternating normal and reverse magnetism parallel to the mid-ocean rift and symmetrical around it: and this is in fact what we see.
The change in static stress then promoted almost-concurrent rupturing along at least 35 kilometres of the ridge axis, where tectonic stress had built up to a critical level, triggering magma movement.
The location of impulsive seismic events indicative of lava reaching the seafloor magma lenses (reservoir chambers) with variable magma ascent rates, mostly within 48 hours.
As the lithospheric plates move apart, this makes a gap into which magma intrudes; it also reduces the pressure on the athenosphere below, causing partial melting of the mantle material.So, for example, marine carbonates settle on the mid-Atlantic rift and rise, because in those shallow waters are above the carbonate compensation depth.Further out, where the waters are deeper, only pelagic clay will settle. Bohnenstiehl for providing the T-wave earthquake catalogue. W., analysed the seismic data and wrote the manuscript.