Summary: It is well-known that while the analogue of Liouville’s theorem on diophantine approximation holds in finite characteristic, the analogue of Roth’s theorem fails quite badly. We associate certain curves over function fields to given algebraic power series and show that bounds on the rank of the Kodaira-Spencer map of this curves imply bounds on the diophantine approximation exponents of the power series, with more “generic” curves (in the deformation sense) giving lower exponents. If we transport Vojta’s conjecture on height inequality to finite characteristic by modifying it by adding a suitable deformation theoretic condition, then we see that the numbers giving rise to general curves approach Roth’s bound. We also prove a hierarchy of exponent bounds for approximation by algebraic quantities of bounded degree.