Chemical Composition of Seawater

70% of earth’s surface is covered in water – let’s see what’s in that water!

What is actually in seawater?Every naturally occurring element on earth has been found in seawater.Obviously, seawater is mostly water!The rest of seawater is composed of the following

Seawater is ConsistentLaw of Constant Proportions:The ions in the world’s oceans remain relatively constant.In other words…In almost all of the world’s oceans the ratios of each ion to one another remain the same:

55% chloride:31% sodium:8%sulfate:4%magnesium:1%calcuim:1%potassium

Q: Can you think of a place that might be the exception to this rule?A: Where rivers meet the sea…river water frequently contains more calcium ions

How did the salt get to the sea?

Salt is added to ocean water by…

• Weathering: On land, rivers carry eroded rock and mineral debris containing salts out to the sea

• Seismic Activity: In the deep sea, underwater volcanoes & vents react with seawater and spew lava, rock, and/or mineral debris containing salts into the sea around them

Salt is removed from ocean water by…

• Sea Spray: We will see evidence of this at Sunken Forest in the spring. Have you seen it on your sunglasses after a day at the beach? (remember Evaporites?)

• Sediment Deposits: as sediment falls to the seafloor, sometimes it binds to minerals in the water around it or just gets buried

• Biological Activity: through the processes associated with life, marine animals and plants sometimes take in salts from the water around them

Q: Why aren’t the oceans getting saltier?

Watch and review: http://www.oceanclassrooms.com/resources/storyline/unit3/MS101_U3_C1_SA_1/story.html