Transport reduction was shown to allow finely controlling the Fe⁺³/Fe⁺² ratio in iron-oxygen two-dimensional nanostructures (nanolayers, thickness 3-15 Å) on silica. It was found by Mössbauer spectroscopy that isolated surface iron-oxygen groups →-Si-O-Fe(OH)₂ and (→Si-O-)₂FeOH are not reduced at 400-600°C, which is explained by their covalent bonding with silica. The transport reduction of samples with applied nanolayers (one and four) at T ≥ 600°C was shown to form bulk phases [iron(II) silicate and metallic iron] on the silica surface. The features of structural-chemical transformations on transport reduction of iron-oxygen nanolayers on supports are primarily associated with the specifics of phase formation in nanostructures.