The structure, the construction and the emplacement of paleovolcanic submarine units are presented through comparisons with recent flows, observed and sampled on active oceanic ridges. The chosen sites are situated: in mesozoic ophiolitic complexes showing well-preserved volcanic morphologies (French and Swiss Alps), in quaternary shallow-water flows (Sicily, Italy) and on the East Pacific Rise at 13°N. Various factors governing the effusion of submarine flows are discussed: depth of water, underlying topography, rate of effusion, viscosity of lava, piles construction, formation of breccias, gravity transports, presence of hyaloclastites. The sampled rocks are olivine + plagioclase (±Cpx) basalts; these are all MORB-type tholeiites, but etnean lavas tend to within-plate transitional basalts. Looking at the interior of the lava tubes, petrographic data on spherolitic/variolitic rim-textures, allow to follow the crystallization and growth of variolites from abyssal recent flows to ancient weathered volcanic units, where they are especially well developed.