Earth is two-thirds ocean. Seas are getting warmer and more acidic; their food supply is decreasing. We will explore physical oceanography (waves, tides, currents); plate tectonics (ocean spreading ridges, trenches, subduction zones, raised marine terraces); marine geology (marine sediments, active coasts, sea cliffs, sea stacks); passive coasts (beaches, barriers); and marine biology (coastal marshes, mangrove swamps, reefs).