<P> It has been estimated that there are 1,386 million cubic kilometers of water on Earth . This includes water in liquid and frozen forms in groundwater , oceans , lakes and streams . Saltwater accounts for 97.5 % of this amount . Fresh water accounts for only 2.5 % . Of this fresh water , 68.9 % is in the form of ice and permanent snow cover in the Arctic , the Antarctic , and mountain glaciers . 30.8 % is in the form of fresh groundwater . Only 0.3 % of the fresh water on Earth is in easily accessible lakes , reservoirs and river systems . The total mass of the Earth 's hydrosphere is about 1.4 × 10 tonnes , which is about 0.023 % of Earth 's total mass . About 20 × 10 tonnes of this is in Earth 's atmosphere ( for practical purposes , 1 cubic meter of water weighs one tonne ) . Approximately 71 % of Earth 's surface , an area of some 361 million square kilometers ( 139.5 million square miles ) , is covered by ocean . The average salinity of Earth 's oceans is about 35 grams of salt per kilogram of sea water ( 3.5 % ) . </P>
<P> It has been estimated that there are 1,386 million cubic kilometers of water on Earth . This includes water in liquid and frozen forms in groundwater , oceans , lakes and streams . Saltwater accounts for 97.5 % of this amount . Fresh water accounts for only 2.5 % . Of this fresh water , 68.9 % is in the form of ice and permanent snow cover in the Arctic , the Antarctic , and mountain glaciers . 30.8 % is in the form of fresh groundwater . Only 0.3 % of the fresh water on Earth is in easily accessible lakes , reservoirs and river systems . The total mass of the Earth 's hydrosphere is about 1.4 × 10 tonnes , which is about 0.023 % of Earth 's total mass . About 20 × 10 tonnes of this is in Earth 's atmosphere ( for practical purposes , 1 cubic meter of water weighs one tonne ) . Approximately 71 % of Earth 's surface , an area of some 361 million square kilometers ( 139.5 million square miles ) , is covered by ocean . The average salinity of Earth 's oceans is about 35 grams of salt per kilogram of sea water ( 3.5 % ) . </P>
hydrosphere covers how much of earth 's lithosphere
hydrosphere covers how much of earth 's lithosphere
71 % an area of some 361 million square kilometers ( 139.5 million square miles )
71 % an area of some 361 million square kilometers ( 139.5 million square miles )