WEBVTT 1 00:00:04.103 --> 00:00:08.763 What I'm looking at right now are these really bulbus pillow flows. 2 00:00:08.763 --> 00:00:12.483 They're really rich in volcanic glass. That lava that's been 3 00:00:12.483 --> 00:00:15.003 erupted on the seafloor has quenched and cooled really 4 00:00:15.003 --> 00:00:18.323 quickly and that's preserved this glassy state of that lava 5 00:00:18.323 --> 00:00:22.203 that we use for subsequent geochemical analysis. The crust 6 00:00:22.203 --> 00:00:28.383 itself is about over 90% silicate minerals. While most of the 7 00:00:28.383 --> 00:00:32.183 ocean's silica input comes from rivers, about 20% comes from 8 00:00:32.183 --> 00:00:35.183 weathering of the seafloor including pillow basalts like 9 00:00:35.183 --> 00:00:39.703 these. And so what's always interesting to me is these 10 00:00:39.703 --> 00:00:44.263 biological organisms that also have silica-based skeletons and 11 00:00:44.263 --> 00:00:47.903 how they depend on the silica that's in the water column that 12 00:00:47.903 --> 00:00:51.143 might be derived ultimately from volcanic products to build 13 00:00:51.143 --> 00:00:53.703 their skeletons. It's interesting that you say that, we just 14 00:00:53.703 --> 00:00:58.623 passed over two glass sponges, the Hexactinellida, the glass sponges. the 15 00:00:58.623 --> 00:01:01.743 glass in the name refers to all the silica that they've 16 00:01:01.743 --> 00:01:04.183 incorporated into their skeleton and one of the cool 17 00:01:04.183 --> 00:01:07.343 things is to think about how all of these elements of the 18 00:01:07.343 --> 00:01:10.823 Earth are interconnected because to get the silica to 19 00:01:10.823 --> 00:01:13.983 deposit in the skeleton, they have to take it out of the water and 20 00:01:13.983 --> 00:01:16.503 where is it coming from the water? It's probably dissolved 21 00:01:16.503 --> 00:01:20.623 or has been released from the interior of the Earth or the 22 00:01:20.623 --> 00:01:24.023 weathering of the rocks that you were just talking about. In 23 00:01:24.023 --> 00:01:26.423 one study that's been published, it's been shown that 24 00:01:26.423 --> 00:01:30.223 sponges can take up approximately 36% of the silica 25 00:01:30.223 --> 00:01:35.783 that's dissolved in seawater. It's a one big cycle.