Siltation-the pollution of water by fine particulate terrestial clastic material with a particle size dominated by silt or clay. red tide- a discoloration of seawater caused by bloom of toxic and dinoflagellates. ozone layer-a layer in the earths a stretosphere at an altitude of about 6.2miles containing high concentration of ozone with absorbs of the ultraviolet radiation reaching the earth from the sun. global climate change-refer to an increase in average global change temperatures.