Sonar and the Ocean Floor

This lesson plan is for Grade 6.

Goals

  1. Students will see how technology is derived from science, and put to everyday use
  2. Learn how the fundamental properties of waves
  3. Learn proper data collection and display techniques

Objectives

  1. Learn the basic physics of sonar and the propagation of sound waves in different mediums
  2. Examine and chart a model of an ocean basin using “sonar”
  3. Graphically illustrate collected data to reproduce the seafloor
  4. Draw connections between the bathymetry of an area and the effects on upwelling, currents, and marine life
  5. Introduction to plate tectonics

Prerequisites

  1. * Properties of waves (Harcourt 2006 pp 534-541)
  2. * Mapping ocean floor (Harcourt 2006 pp 345-351)
  3. * Plate Tectonics (pp238-245) – “How Earth’s Plates move” activity

Benchmarks (Hawaii)

  • 6.1.2
  • 6.2.1
  • 6.2.2
  • 6.6.1

Materials

  1. Bathymetry boxes (http://www.dosits.org/teacher/activity/Box_directions.pdf)
  2. Bathymetry foam layouts (http://www.dosits.org/teacher/activity/Box_directions2.pdf)
  3. Worksheets (http://www.dosits.org/teacher/activity/Inside_the_Box_Middle-High.pdf)
  4. One 12-inch long wooden dowel per box
  5. Colored markers/crayons or MS Excel
  6. Rubber ball
  7. Nautical/bathymetric charts of Hawai

Resources

  1. Think Inside the Box – Lesson on Sonar and Bathymetry – http://www.dosits.org/teacher/activity/activity.htm#think –Humans and marine mammals use sound waves in water (sonar) to map the environment, and this site has several lessons and activities related to sound and its propagation through water. Students can build a hydrophone, listen to whale songs, and much more.
  2. Alternative lesson plan for bathymetry boxes (http://www.sea.edu/academics/k12.asp?plan=unseenoceanfloor)
  3. NOAA Learning Objects – Lesson 15: Seamounts (http://www.learningdemo.com/noaa/)
  4. Oceans Alive (http://www.oceanslive.org/portal/index.php?module=pagesetter&tid=1&filter=audience:eq:2&tpl=home-list&orderby=core.created:desc&pubcnt=3) – Video for Hawaiian Hot Spot and Plate Tectonics; explains fault lines, subduction zones, and volcanism.

Lesson Description

The teacher will introduce the children to the concept of sonar waves (students should already be familiar with the components of waves).  Using the rubber ball to stand for a sonar wave and bouncing it off of a wall from increasing distances, the teacher can demonstrate that since sound waves travel at a constant speed (1500m/s in water) they can be used to measure distances (the ball takes longer to bounce back to teacher when the teacher is further from the wall). The components of waves will be reviewed and vocabulary stressed (e.g. wavelength, crest, trough, frequency, etc.).

The exercise consists of using a wooden dowel rod to “sample” the ocean bottom, made from dry foam in a closed box (pre-made by teacher ahead of time, one box per group). Students will take measurements and plot their findings to create a bathymetric model of the seafloor while looking for the best route to lay a telecommunications cable.  Detailed lesson plan is found above in the resource section.  Emphasis should be placed on the fact that students are measuring the time the signal takes to reflect off the bottom, and thus it represents the distance traveled, which is double the depth. Students will sample at two different resolutions, using lids with different spacing to illustrate the concept of spatial resolution and data collection.

Many people think of the ocean floor like that of a lake or pond, when in reality it has incredible mountain ranges and canyons, some bigger than anything seen on dry land.  The ocean basin is shaped by the natural geological processes of our planet, so this lesson lends itself to discussions of plate tectonics, hot spots, and volcanoes.  Hawaii is a very specific example of these processes.

This unit can be tied to the Niu since underwater bathymetry plays a role in shaping local currents and wave patterns. Using a topographic map of the Hawaiian islands and the undersea topography, the teacher can discuss local ocean features that may or may not be relevant to students (e.g. surf breaks, calm beaches vs. rough beaches, the currents that pass by our islands and how the islands themselves shape them).  This unit can be expanded to introduce some of the basic concepts of physical oceanography and marine biology, such as areas of upwelling (See Lesson 15 – Seamounts on the NOAA Learning Objects website).