Shipwreck Alley Lesson Plan
Student Worksheet - Thunder Bay National Marine Sanctuary
- 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?”
- The maritime history of the Thunder Bay region is characterized by the use of, and dependence upon __________________________.
- What is the first recorded use of natural resources in Thunder Bay?
- When did European activity probably begin in Thunder Bay, and for what purpose?
- 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?
- How high is the New Presque Isle Lighthouse?
- Middle Island Lighthouse is about halfway between what two locations?
- What provided power for the original fog signal on the Thunder Bay Island Lighthouse?
- What are local slogans for the Thunder Bay River (or Alpena) Lighthouse?
- Why was the Sturgeon Point Lighthouse constructed?
- What type of vessel was the John J. Audubon? When and how was the vessel lost?
- What type of vessel was the Isaac M. Scott? How was the vessel lost? Were any mariners lost with the ship?
- What were two mishaps suffered by the New Orleans before the final mishap that caused the vessel to sink? What was the final mishap?
- What type of vessel was the Pewabic? What caused the Pewabic to sink? What valuable cargo was the Pewabic carrying?
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?