Shipwreck Alley

Thunder Bay National Marine Sanctuary / Grades 9-12 / Geography, Physical Science, Math

Focus Question

How is it possible to reduce dangers to ships from natural hazards in the Great Lakes?

Links to Overview Essays and Resources Useful for Student Research


Audio/Visual Materials

Teaching Time

Seating Arrangement

Maximum Number of Students


Key Words

Fresnel lens


Background Information

“Shipwreck Alley” is the final resting place for scores of ships that have fallen victim to Lake Huron’s murky fog banks, sudden gales, and rocky shoals. In October 2000, the Thunder Bay National Marine Sanctuary and Underwater Preserve was established in a 448-square mile area that includes an estimated 116 historically significant shipwrecks. These range from from wooden schooners more than 150 years old to sidewheel steamers to modern freighters. The cold, fresh waters of Lake Huron slow down natural processes that corrode iron and degrade wood, so even the oldest shipwrecks are often in excellent condition. The shipwrecks of Thunder Bay tell us a great deal about life on the Great Lakes over the past 200 years, and offer opportunities to study the structure, rigging, and other details of sailing ships that are hard to find anywhere else.

In this lesson, students will investigate some of the history of the Thunder Bay area, as well as the physical principles underlying efforts to make the area safer for shipping.


Learning Procedure

  1. If you want to introduce your students to marine protected areas, direct them to the MPA education poster "Site Descriptions” and the “MPA Poster Activity Sheet" at and Have each student complete one version of the MPA Subject Review, then lead a discussion to review the answers.

  2. Have each student or student group complete Part I of the “Thunder Bay National Marine Sanctuary Worksheet” and one or more problems in Part II of the worksheet. Information for Part A of this worksheet can be found on the Thunder Bay National Marine Sanctuary and Underwater Preserve website at

    Click here for a separate printable copy of the worksheet. Click Here for separate printable copies of worksheet appendix A, and appendix B

  3. Lead a discussion of students’ answers. The following points should be included in this discussion:

The surface area of the side is π •D• h = 3.14 (1 m) • 3 m = 9.42 m2
The surface area of one end is π • (radius of the end)2
= 3.14 • (0.5 m)2
= 3.14 • 0.25 m2
= 0.785 m2
So the total surface area of the cylinder is 9.42 m2+ (2 • 0.785 m2) = 10.99 m2.

The volume of steel used in the cylinder is the total surface area of the cylinder multiplied by the thickness of the steel used to construct the cylinder, so
volume of steel = 10.99 m2. • 6 mm
= 10.99 m2. • (6 x 10-3 m)
= 6.59 x 10-2 m3.

So, the weight of the buoy is
(volume of steel) • (density of steel)
= (6.59 x 10-2 m3) • (7,850 kg/ m3)
= (6.59 x 10-2 m3) • (7.85 x 103 kg/ m3)
= 5.18 x 102 kg

The buoyant force acting on the buoy is equal to the mass of water displaced by the buoy. This is equal to the volume of the buoy multiplied by the density of water. So,
volume of the buoy = 3.0 m • π • (0.5 m)2
= 3.0 m • 3.14 • 0.25 m2
= 2.36 m3

mass of water = 2.36 m3• 1.0 gm/cm3
since 1 m3 = 1 x 106 cm3, mass of water = 2.36 x 106 cm3 • 1.0 gm/cm3
= 2.36 x 106 gm
= 2.36 x 103 kg

So the buoyancy when completely submerged will be equal to
(buoyant force) - (weight of the buoy)
= (2.36 x 103 kg ) - (5.18 x 102 kg)
= 1.842 x 103 kg

Since the weight of the anchor system must be twice the buoyancy of the submerged buoy, the anchor system must weigh
2 • 1.842 x 103 kg = 3.68 x 103 kg.

The anchor system will include 20 meters of anchor chain. Since the chain weighs 4 kg/m, the total length of chain will be 80 kg. So the required weight at the bottom of the chain must be
(total weight of the anchor system) - (weight of the chain)
= (3.68 x 103 kg) - (80 kg)
= 3.6 x 103 kg

Be sure students understand that this must be the NET weight of the bottom anchor; that is, the weight of the anchor in air, minus the mass of the volume of water that the anchor displaces.


The Bridge Connection

The Bridge is a growing collection online marine education resources. It provides educators with a convenient source of useful information on global, national, and regional marine science topics. Educators and scientists review sites selected for the Bridge to insure that they are accurate and current. - Click “Ocean Science Topics” in the navigation” menu on the left, then “Human Activities,” then “Heritage,” then “Archeology” for resources on marine archeology and lighthouses.

The “Me” Connection

Have students write a brief essay in which they describe the cultural landscape of their community, identify natural and cultural resources of particular importance or significance, and recommend appropriate ways to protect these resources.


Visit for more information about Prehistory and Native American History, Settlement and Early Transportation, Lighthouses and Life-Saving Stations, Vessel Types, and Economic Activities in the Thunder Bay region.


Resources - Web site for the National MPA Center, with definitions, program descriptions, list of MPA sites, virtual library, tools, and links to regional information centers. - The Great Lakes Shipwreck File: Total Losses of Great Lakes Ships 1679 - 1999 by Dave Swayze, Lake Isabella, MI. - “Vessel Types” page of the Thunder Bay National Marine Sanctuary and Underwater Preserve Web site. - “Lighthouses and Life-Saving Stations” page of the Thunder Bay National Marine Sanctuary and Underwater Preserve Web site. - A brief explanation of Fresnel lenses. - A short article about Augustin Fresnel and lighthouses. – Exploratorium “snack” on Fresnel lenses.

National Science Education Standards

Content Standard A: Science as Inquiry

Content Standard B: Physical Science

Content Standard E: Science and Technology

Content Standard F: Science in Personal and Social Perspectives

Content Standard G: History and Nature of Science


Ocean Literacy Essential Principles and Fundamental Concepts

Essential Principle 6. The ocean and humans are inextricably interconnected.


Shipwreck Alley Lesson Plan

Student Worksheet - Thunder Bay National Marine Sanctuary

Part I

  1. The Thunder Bay National Marine Sanctuary and Underwater Preserve is focussed on understanding the region’s maritime cultural landscape. What is a “maritime cultural landscape?”

  2. The maritime history of the Thunder Bay region is characterized by the use of, and dependence upon __________________________.

  3. What is the first recorded use of natural resources in Thunder Bay?

  4. When did European activity probably begin in Thunder Bay, and for what purpose?

  5. How many lighthouses are located within or near the Thunder Bay National Marine Sanctuary and Underwater Preserve? How many are still used as navigational aids?

  6. How high is the New Presque Isle Lighthouse?

  7. Middle Island Lighthouse is about halfway between what two locations?

  8. What provided power for the original fog signal on the Thunder Bay Island Lighthouse?

  9. What are local slogans for the Thunder Bay River (or Alpena) Lighthouse?

  10. Why was the Sturgeon Point Lighthouse constructed?

  11. What type of vessel was the John J. Audubon? When and how was the vessel lost?

  12. What type of vessel was the Isaac M. Scott? How was the vessel lost? Were any mariners lost with the ship?

  13. What were two mishaps suffered by the New Orleans before the final mishap that caused the vessel to sink? What was the final mishap?

  14. What type of vessel was the Pewabic? What caused the Pewabic to sink? What valuable cargo was the Pewabic carrying?

Part II

The many shipwrecks that are part of Thunder Bay’s history have resulted in major efforts to reduce the hazards faced by mariners who sail on Lake Huron. One of the most prevalent efforts has been the installation of “aids to navigation” (ATONs) that mark hazards and provide guidance to safe routes into ports and harbors. One of the oldest and most familiar ATONs is the lighthouse. The Colossus of Rhodes and Pharos of Alexandria (two of the “Seven Wonders of the World”) were lighthouses used to mark the entrances to the harbor on the Greek island and the Nile estuary. Like modern lighthouses, the basic idea was to have a bright light that is high enough to be seen from far off shore. Often, lighthouses also include sound producing devices for fog, radio beacons, weather instruments and other equipment. The markings on lighthouses allow them to be identified during the day, while the color and flashing pattern of the light provide identification at night.

Buoys are another familiar ATON that consist of various types of floating markers anchored to the bottom. Most buoys are shaped like cylinders (“can” buoys) or cones (“nun” buoys), and have specific colors that correlate with the buoy’s purpose. Can buoys are green, have odd numbers, and are used to mark the left side of a channel (when entering from offshore). Nun buoys are red, have even numbers, and mark the right side of a channel (when entering from offshore). Buoys painted with red and green stripes mark the center of a channel (the top color indicates whether it is best to pass to the left or right of the buoy). Yellow buoys are used on the Intracoastal Waterway in the United States; orange and white buoys are regulatory or informational; black markers are state or private buoys; and blue and white markings are used on mooring buoys. Some buoys have devices that make sounds so they can be identified under foggy conditions, including bells, gongs, whistles, and horns. Many buoys also have lights that may be green, white, yellow, or red, depending on the buoy’s function. The lights may be steady (“fixed”) or flashing.

Ranges are a third type of ATON that are not as familiar as lighthouses and buoys. Ranges are structures built onshore to indicate the center line of a channel, and are always found in pairs. The two elements of the range are built at different heights, with the highest structure farthest from the water. When the two structures appear to be lined up, one on top of the other, a mariner’s vessel is in a safe channel.

Problem 1: Buoy Oh Buoy!

Your assignment is to design an anchor system for a can buoy to mark the left side of a narrow channel in Thunder Bay. The buoy will be a cylinder with a height of 3 meters and a diameter of 1 meter. The buoy will be constructed of steel plate having a thickness of 6 mm. The weight of the anchor system should be twice the buoyancy of the buoy if the buoy were completely submerged (as in a severe storm). The anchor system will include a bottom weight and anchor chain. The buoy will be deployed in an area where the bottom depth is 20 meters. How heavy should the bottom weight be to meet these requirements?

For purposes of your calculations, assume:

  • the density of the steel used to construct the buoy is 7,850 kg/m3 ;
  • the density of water in Thunder Bay is 1.0 gm/cm3; and
  • the anchor chain will be absolutely vertical when the buoy is in place, with no slack chain between the buoy and the anchor, and will weigh 4 kg/m

Problem 2: Current Affairs

Refer to Figure 1. You are skipper of a motor vessel located at point A. You want to anchor in Safe Harbor. To enter the harbor, you have to line up the two range lights shown on the chart. There is a 2 knot (a knot is one nautical mile per hour) current setting to the southeast (135°). What course should you steer, and what speed should you make in order to reach the closest point on the range in 30 minutes? You can use the latitude scale on the right side of the chart to find distances, since one minute of latitude is equal to one nautical mile.

Problem 3: Shine Your Light

Until the 19th century, lighthouses were basically a source of light, ranging from candles to a bonfire, mounted on a high platform. Even though some of these platforms were quite elaborate (like the Colossus of Rhodes), the basic idea was fairly simple. In 1822, though, lighthouse technology took a giant leap forward thanks to a new invention. What was this invention, and how does it work?

Click here for a printable version of this page


Shipwreck Alley Lesson Plan

Student Worksheet - Thunder Bay National Marine Sanctuary

Part II, Problem 2: Current Affairs: Figure 1


Shipwreck alley lesson plan. Student worksheet appendix 1: Current Affairs

Click here for a printable version of this page



Shipwreck Alley Lesson Plan

Student Worksheet - Thunder Bay National Marine Sanctuary

Part II, Problem 2: Current Affairs: Figure 2



Shipwreck alley lesson plan. Student worksheet appendix 2: Current Affairs

Click here for a printable version of this page


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