[OlympusMonds]

Yes, you're right, it is the isostatic unloading that they're referring to - but in regards to the 'sucking', they seem to mean that the semi-localised unloaded of the top of crust (via rain, river incision) creates a zone of lower lithostatic pressure, and so that area ends up getting pushed up to maintain isostatic equilibrium. Not truly a 'sucking', but as an analogy, I think it's OK. It's more easily seen as part of the critical wedge angle for fold and thrust belts.

[bigbubba]

Does anything truly 'suck'? When you drink a milkshake with a straw, the milkshake is pushed up your straw by the atmosphere..

[OlympusMonds]

Exactly, good point. It is convenient short-hand term, and in the case of climate forcing tectonic activity, it works well, I think.

[geoid]

Fair. 'sucking' does work to describe the unloading. I guess the idea that the _speed_ of the erosion creates suction, is what bothered me.