September equinox solar radiation tectonic subduction tectonic subduction tectonic subduction subduction zones tectonic subduction zones sedimentary rocks Schist shale Slate subduction zones Stefan-Boltzmann tectonic Schist September equinox September equinox tectonic subduction Slate sills Slate seasons sills tectonic subduction seasons sandstone shields Slate sills sills September equinox September equinox shields sedimentary rocks Schist Slate sedimentary rocks Schist tectonic subduction subduction sandstone subduction zones subduction sandstone subduction zones shale tectonic September equinox shields sandstone seasons shields subduction zones sills shields sills subduction zones subduction Slate Schist tectonic subduction shale sandstone shale shields September equinox Schist tectonic tectonic seasons shields tectonic subduction September equinox shale sandstone subduction seasons shields sandstone Slate subduction zones tectonic subduction shale sills sandstone Slate seasons tectonic subduction sandstone tectonic subduction scattered Slate sedimentary rocks Schist seasons shields subtropical highs tectonic subduction tectonic tectonic Schist Schist subduction Schist sills sills tectonic sedimentary rocks subduction sills subduction shale shields sedimentary rocks sedimentary rocks Stefan-Boltzmann shale sandstone subduction zones subduction sedimentary rocks shale Slate seasons sedimentary rocks subduction zones shale sedimentary rocks