SEAFLOOR PROFILING—Lesson #1: Introduction
Materials per group (2-4) of students:
Seafloor Profiling Data Table shoe box
Blocks of wood metric ruler paper & pencil
Yakitori skewer/lei needle graph paper
Procedure/Assessment for Lesson #1:
(1) If necessary, review graphing skills with the students before starting this lesson.
(2) It is suggested that the lesson be done in two days. See below.
(3) It is suggested that this lesson be started by telling students that mapping is important in many human endeavors, including science. When people arrive in a new place, they immediately need to map where they are and how they got there, so that they can find their way back home, or so they can communicate to others who might want to follow them. Explorers, like Columbus, made lots of maps! Mapping of the moon and planets is an important component of modern space exploration. It is the same for the ocean; scientists want to have accurate maps of the seafloor. Certainly, sailors and sea captains want to know where there are reefs and shallow areas so they won’t run aground!
This introductory lesson mimics the earliest method of seafloor mapping as practiced by the ancient Greeks in 85 B.C. A rope with a weight at the end was lowered over the side of the boat or ship until the weight touched bottom.
Day #1 methods:
(1) The shoebox represents an ocean. The bottom of the box represents the bottom of the ocean; the sides represent where the seafloor rises to the sea surface to join a continent; the shoebox top represents the sea surface. So, the volume of an ocean is like the volume of the box.
(2) Add blocks of wood to the shoebox; these now represent the seafloor, instead of the shoebox bottom under them. By adding blocks, you can change the shape and depth of the seafloor of your “ocean.” In some places put one or two blocks of wood to make the seafloor about half way between the box bottom and the shoebox lid. In other places, add blocks to reach almost to the lid. Finally, leave the box bottom bare to represent really deep seafloor.
(3) When you have made your “seafloor,” close the lid. Start at one end of the shoebox and poke a hole through the lid with the yakitori skewer. Push the skewer in until it touches the bottom of the ocean floor that you have built.
(4) With your thumb and fore finger, pinch the skewer at the point where it went in through the lid. Remove the skewer, and use the metric ruler to measure from the tip of the skewer to your thumb and finger. Record this measurement, which represents the depth of your ocean at that point. Record this measurement in the Data Table.
(5) On the shoebox lid label the hole “start,” and draw a line from the hole you made directly across the length of the shoebox to the other side. Use the metric ruler to mark this “transect line” every 2 centimeters. Label the last 2 cm mark as “end.”
(6) Repeat steps 3 and 4 along the transect line, poking the skewer through the lid and measuring the depth of the ocean every 2 centimeters. As you do this, think to yourself that you are an oceanographer sailing across the ocean surface, stopping every now and then to measure how deep the ocean is! Record all measurements in “Seafloor Profiling Data Table.”
(6) When you have completely mapped the ocean floor, make a line graph of your data. The X-axis represents the sea surface. Put “start” at the origin and “end” at the proper place farther out on the X-axis. The Y-axis represents the depth of the seafloor; so it should project down, below the X-axis, not upward, as it usually does.
(7) Congratulations! You have successfully created an ocean with a varied seafloor! The graph represents the “profile” of your seafloor’s shape. Even though your seafloor ocean is a made-up ocean, for fun, choose the name of a real Earth ocean or sea to name your seafloor; write the name on your box and on your graph.
Day 2 methods:
(1) Check to see that the seafloor of your ocean has not changed – that no blocks have shifted. If they have, rearrange them correctly.
(2) When your teacher gives the okay, exchange shoebox “oceans” with another group of students, but each group should give the graph seafloor profile for its ocean to the teacher.
(3) Use the procedure you used yesterday to measure the ocean depth of this new ocean. Enter the data in another “Seafloor Profiling Data Table”, and then draw a line graph of the seafloor profile for this ocean.
(4) When you are done with step 3, ask the teacher to let you look at the “answer sheet,” which is the graph of this ocean made by the group of students that created the seafloor. How would you evaluate your accuracy? Use this scale –
Oceanographer = excellent; pretty close to 100% accuracy!
Science apprentice = good; more that 50% accurate!
Sand castle builder = ships would run aground if they used your profile!