What I'm looking at right now are these really bulbus pillow flows.
They're really rich in volcanic glass. That lava that's been
erupted on the seafloor has quenched and cooled really
quickly and that's preserved this glassy state of that lava
that we use for subsequent geochemical analysis. The crust
itself is about over 90% silicate minerals. While most of the
ocean's silica input comes from rivers, about 20% comes from
weathering of the seafloor including pillow basalts like
these. And so what's always interesting to me is these
biological organisms that also have silica-based skeletons and
how they depend on the silica that's in the water column that
might be derived ultimately from volcanic products to build
their skeletons. It's interesting that you say that, we just
passed over two glass sponges, the Hexactinellida, the glass sponges. the
glass in the name refers to all the silica that they've
incorporated into their skeleton and one of the cool
things is to think about how all of these elements of the
Earth are interconnected because to get the silica to
deposit in the skeleton, they have to take it out of the water and
where is it coming from the water? It's probably dissolved
or has been released from the interior of the Earth or the
weathering of the rocks that you were just talking about. In
one study that's been published, it's been shown that
sponges can take up approximately 36% of the silica
that's dissolved in seawater. It's a one big cycle.