A globe or atlas shows fresh and salt
water masses as being the same. However, one infers that the large
bodies of water are usually salty while the smaller bodies of water are
Point out that not all salt water is the same.
The amount of salt is measured by its salinity which is measured by parts
per thousand of that salt in water. For instance normal salinity of
the major oceans is around 35-36 o/oo (read parts per thousand), but some
bodies of water like Great Salt Lake in Utah has a salinity much higher
than seawater. You may want to discuss with students where there
may be more salinity than others. In places where evaporation is
high there is a higher salinity. If there is a lot of precipitation the
salinity would be less because rain water is fresh water. In waters
where there are icebergs, the salinity would be higher because the icebergs
are fresh water and the salt gets concentrated. But if the icebergs
melt, it adds fresh water and the salinity goes down. The oceans
are a complicated place!
- You might want to make a
list of the bodies of water that are fresh and salty. You should
introduce the term "marine" which is the correct way of referring to salty
water. Salt water examples include Pacific Ocean, Indian Ocean, Great
Salt Lake, Salton Sea in southern California, and Mediterranean Sea to
name a few. Fresh water examples include the Great Lakes, Lake Tahoe,
Mississippi River, and local reservoirs. Potential fresh water is
tied up in icebergs, ice sheets, and glaciers. Antarctica is a large
source of fresh water.
- Students can color the different parts
of the globes and label the different parts. You might want them
to use a lighter blue for fresh water. So, for instance around Antarctica
(D) you might want another shade of blue that is between fresh and normal
salinity. This would also hold true for the Arctic Ocean (C).
Since there are polar caps there, you might suggest that student color
it gray to represent ice sheets.
- Main areas students should identify
is the following:
- Africa, Eurasia, Indian Ocean, Atlantic Ocean,
Caspian Sea (salt), Black Sea (salt), Red Sea (salt), Mediterranean
- Atlantic Ocean, Pacific Ocean, South American,
North America, Great Lakes (fresh)
- Arctic Ocean, ice caps (fresh), Eurasia, North
America, Pacific Ocean, Atlantic Ocean
- Antarctica, ice sheets (fresh), Indian Ocean,
Atlantic Ocean, Pacific Ocean.