changes in sea level

• Sea level rise is called marine transgression. 
• Sea level drop is called marine regression. 
• In transgression the rock sequence goes sandstone, mudstone and limestone. 
• In regressions the rock sequence goes limestone, mudstone and sandstone - starting from the bottom. 
• Global eustatic change is either changes in volume of water in oceans or changes in volume of ocean basins. 
• Volume of water:

  Water needs to be locked up on land, if antarctica melted sea levels would rise by 75m. Melting of ice caps is very rare. 
• Volume can also change due to contraction or expansion from changes in temp. 1ºc increase in 500m of water causes 10cm rises. Thermal expansion has a much smaller effect. 
• Volume of ocean basins:

  Lots of new ocean spreading ridges occupy more volume decreasing volume in ocean basins, causing sea level rises. 
• As sea levels drop continental shelves become land, reducing habitat for shallow water organisms. 
• Sea level rise produces large areas of warm, shallow water, leading to a high species diversity. This high nutrient waters trigger plankton blooms, decomp of the blooms requires oxygen creating anoxic conditions. Some sessile organisms cannot adapt to rising water, and increases competition. 
• Water has a low albedo so will absorb solar radiation, more water means increasing temperatures. 
• On the Permian-Triassic boundary some scientists say there was transgression some say regression.