Activity
Part One
1. If you have access to a television and VCR, begin by
showing the class an excerpt from the film Message in a
Bottle. (Show the part where the reporter is looking at
a map showing all the sightings of the sailor’s bottled
letters to his wife.) Where else have they heard of messages
being sent in bottles? Do they think it is a reliable way
to communicate? [If you do not have access to the above,
ask students to tell you stories they have heard of where
sailors are stuck on deserted islands. According to the
stories what do those sailors almost always do? Why? Do
they think it is a reliable way to communicate?]
2. Tell students that today they will be responsible for
finding a different lost sailor using messages in bottles.
Each group will be given a series of locations where the
bottles were found either on a shore, or in the ocean by
other vessels. Their task is to plot those locations on
a map to see if they can use that data to determine where
the sailor was when he or she threw the bottle into the
ocean. Review with students the use of Cartesian coordinates
to plot locations. Explain to the students that many world
maps are laid out on a similar rectangular grid. Pass out
the Mercator Projection maps. (This map can be found at
http://alabamamaps.ua.edu/world/world/world2.pdf) Explain
that Mercator Projection is different because the grid
is rectangular and this causes distortion in the size of
the countries as you move closer to the poles.
3. Have the students find and darken the lines representing
the equator and Prime Meridian on the map. Tell the students
that the point of intersection of these two lines is the
origin from which coordinates are calculated. The darkened
lines also divide the projection into four quadrants, which
are labeled quadrants I, II, III, and IV in their standard
positions as if on a coordinate plane. Ask the students
to tell you the quadrant the following coordinates are
in:

4.
Tell the students that the quadrants also allow us
to use positive and negative Cartesian coordinates
to find
locations. Ask them, “Looking at the map, which
coordinates would you expect to be positive?” Which
would be negative? (North latitudes and East longitudes
would
be positive while South latitudes and West longitudes
would
be negative). Discuss the importance of which direction
comes first in the coordinate pairs. (Degrees of latitude
come first and then degrees of longitude, which are
backwards
from the normal ways of plotting points as the first
number gives the vertical location and the second number
gives
you the horizontal location). Ask the students the
range of numbers valid for each coordinate. (Degrees
of latitude
can vary from and
degrees of longitude can vary from ) Ask the students
to tell you the quadrant the following
coordinates are in:
i.

5. Distribute world maps and bottle locations. Allow students
1520 minutes to plot their points and determine the direction
of the current that took the bottles. Once students have
finished, have them use an overhead transparency to prepare
a summary of their findings for the class. Inform students
that a blank overhead of the world will be available for
their presentation. (If you have limited funds the overhead
can be left blank and the students can write on their own
overhead; if it is feasible, make sufficient copies of
the map so that each group can have their own copy.)
Part Two
4. Have groups share the locations of the found bottles
with the class and what they believe to be the correct
location of the lost sailor. Invite other groups to question
the findings or suggest possibilities the others might
have overlooked. Emphasize constructive criticism to the
students.
5. As students are listening to presentations, they should
be sketching what they believe to be the overall picture
of global ocean currents in their laboratory notebooks.
Closure
What are the similarities and what are the differences?
How else might we work to determine the way the oceans
move and why? What characteristics of ocean water
might affect its currents?

Embedded
Assessment
Students’ use of Cartesian coordinates to plot
accurately can be assessed during the group practice
of Cartesian coordinates and through the map that they
triangulate the origin of the sailor’s bottled
message. During the group presentation students’ ability
to use plot data to identify which ocean currents carried
the bottles can be assessed. Further are all students
participating? Can they hypothesize a plausible reason
why the ocean moved the bottles where they did?
