El Niño is a periodic warming of ocean waters in the eastern Pacific that occurs every 2-7 years. It causes changes to weather patterns around the world like droughts. Ocean currents are driven by factors like wind and the Coriolis effect. The ocean can be divided into layers with different temperatures and pressures. Tides are caused by the gravitational pull of the moon and sun. They have high and low phases. Salinity measures the salt content in ocean water, which is mostly sodium chloride. Evaporites form when minerals precipitate out of waters with high salinity in areas with high evaporation rates.