| The objective of this study is to quantitatively investigate tectonic and submarine lava flow emplacement processes at mid-ocean ridges. In particular, we wish to examine the tectonic and volcanic contributions to mid-ocean ridge stretching, and to quantitatively simulate the submarine lava flow emplacement process in the mid-ocean ridges.;The Southeast Indian Ridge (SEIR) exhibits significant difference in axial morphology from EPR-type axial high to MAR-type deep axial valley from west to east at a constant spreading rate of 75 mm/yr. A comparison studies of 2 ridge segments with distinct morphology indicate that both fault number and throw pattern are different between two segments. Inward-facing faults form much closer to the ridge axis than outward-facing faults at MAR-type segments and the cumulative throw of inward-facing faults accounts for 78% of the total throw, while both inward-facing and outward-facing faults appear at the same distance off axis at EPR-type segments and their cumulative throws are comparable. A clear tectonic strain pattern, however, is observed at both segments indicated by the presence of lowest tectonic strain at segment center and highest tectonic strain at segment ends. These patterns are the result of different thermal structure and magma supply between two segments and along a single segment respectively.;Submarine lava flows observed along mid-ocean ridges have significant diversity in their size, shape, and morphology. A two dimensional numerical model is developed to simulate the submarine lava flow emplacement process and to study how viscosity, yield strength, topography, effusion rate, and effusion volume affect the lava flow morphology. The latent heat release, thermal conduction heat loss, lava skin growth, and lava tube formation are taken into account in the model. The modeling result indicates that lava flow thickness is mainly controlled by yield strength while the lava flow width is controlled by both viscosity and yield strength. The result also confirms the importance of internal lava tubes as agents delivering lava efficiently with minimal cooling. Lava tubes enable incoming lava to travel long distance beneath cover without significant heat loss. When this happens lava flow length is predominantly controlled by the total effusion volume rather than the effusion rate. Consequently, even low and moderate effusion rates can lead to long lava flows. Applying our numerical model to the lava flows at the ultra-fast spreading Southern East Pacific Rise between 17°28'S and 17°29'S surveyed by 1999 Atlantis cruise gives an estimate of lava effusion volume of 1,680,000 m3 per km along this ridge segment. |
