DO expanding river deltas push up sea levels?

I suspect that any effect would be infinitessimal.

Interesting question! There aren't that many major rivers with substantial deltas and there is a LOT of ocean floor..... I bet Drewdad is right on the net effect. I wonder if the continuously recycling ocean floor -- subduction and spreading -- would help in handling extra material from river silt.

lil k and dad are both right, deltas , as they are emplaced, begin to sink and , over time, they compress and are a wash. The ocean basins are being sucked into the earth along continental margins and they are building up in ascending plate margins and in mid- ocean ridges. The amount of biomass that forms and sinks to the bottom is about2 cm a year all over the planet. The biggest sea level rise cause is the melting ice caps , especially Greenland and parts of Natarctica. Lots of land along the North Margins of Asia, N America and Europe are still rebounding, actually "rising" because theyve been unweighted by the melted glaciers over 9000 years ago.

If the river deltas introduced more and more run-off into the world's oceans (in the immediate future), would subduction (in the distant future) make a difference? <just for the discussion>

subduction is going on now at a rate easily equivalent to all the deltas of the world. Remember , the land masses are sort of "floating " on the mantle anyway, and "trailing edges " of moving landmasses produce way more "beachfront sediment " than deltas.

Eh, I was getting at something slightly different, but I can't put it into words any better than I have......