Figure 7. Global silica reservoirs, fluxes,
and turnover times. Major
reservoirs are underlined, pool sizes and fluxes are given in Tmole (1012 moles) Si and Tmole Si yr-1. Turnover times (reservoir divided by largest flux to or from reservoir ) are in
parentheses. To convert Tmole Si to Tg Si, multiply by 3.6 x 10-2.
The silica cycle is restricted to soild and aqueous phases, as
there are no gaseous silica compounds of geochemical importance. The silica cycle is dominated by ocean processes. Silica released by continental weathering is transported in dissolved and
colloidal form by rivers to the ocean, where the major sink is euphotic zone uptake by planktonic diatoms and radiolarians at high latitudes and in the tropics, respectively.