Lake Superior Local Knowledge

MDK221 2026

Lake Superior’s elevation for the low water datum is

601.1 feet

The length of the steamer track from Duluth Ship Canal to Pt Iroquois is

383 miles

The length of the steamer track from Duluth Ship Canal to Michipicoten Harbor is

350 miles

The breadth of Lake Superior on longitude 86°45’W is

160 ft

What is the maximum depth on Lake Superior

1,333 ft

What is the water surface area of Lake Superior

20,600 sq. mi (US), 11,100 sq. mi (CAN)

What is the entire drainage basin area of Lake Superior

37,500 sq. mi (US), 43,500 sq. mi

Where does Lake Superior gets its water from and drains to

Many short swift/flowing streams which then goes into the St. Marys River which leads to Lake Huron

How is the geography of Lake Superior

Its shores are high, rocky, and forested with the north shore being sparsely populated

How long is the navigation season in Lake Superior

8 months

When is Lake Superior’s water level at its lowest?

close of winter

When is Lake Superior’s water level at its highest?

Late summer

Strong winds drive forward a greater volume of surface water than can be carried off by the lower return currents, thus raising the water level on the ___ and lowering it on the ___

lee shore, windward shore

Fluctuations caused by strong winds seldom exceed ___ above or below the normal level, but may cause changes up to ___

1 ft, 2 ft

The dikes and sluice gates in the river are operated as to maintain the monthly mean level of Lake Superior as nearly as possible between elevations ___ and ___ above the mean water level at Rimouski, QC

599.61 ft, 603.22 ft

Strong winds are a threat from the ____ through ____ seasons over the open waters

fall, spring

_____ is the worst, when gales blow up to ____ percent of the time

Late autumn, 6

The ___ part of the lake is least susceptible since it is somewhat sheltered from the strong winds, many of which have a ___ or ____ component

west, westerly, northerly

Fall windspeeds of 28 knots or more occur ___ percent of the time in this region compared to ______ percent elsewhere

11, 16 - 18

Spring winds are variable, with _____ through ____ winds common in the morning

north, southeast

Where are easterly winds common in?

Duluth and Sault Ste. Marie

Summer winds are often out of the ___ through ___

south, west

Along the shore in morning during the summer, the lake/land breeze results in ___ type of winds

off shore

When are thunderstorms most likely to occur

April through October, particularly June, July, and August

Over open waters, thunderstorms are most likely to occur at what times

Between midnight and 0300

The ___ half of the lake is more vulnerable to thunderstorms than the ___ half

west, east

The lake is large enough for strong winds to create considerable wave action due to the

long fetch

The Keweenaw Peninsula tends to diminish seas generated by ____ and ____ in the south part of the lake

easterlies, westerlies

During the late fall and early winter on Lake Superior, what are the maximum sea heights that have been encountered?

25 to 30 feet

What type of fog would you encounter from spring through fall

advection fog

What type of fog would you encounter during the Fall

radiation fog

What type of fog would you encounter during the winter

ice fog

Which months are considered to be the most fog-prone months

April through August, December

Where do the most vulnerable waters to fog lie between

Keweenaw Pt and Au Sable Pt

What type of phenomenon is fog along the shoreline

morning

___, at the lower end of Lake Superior, is a bottleneck area. The shallow bay forms ice rapidly, and the prevailing west winds jam and pack the lake ice into the area.

Whitefish Bay

The ice in Whitefish Bay can reach an average thickness of ___ inches and an average maximum thickness of ___ inches

14, 22

Windrows in Whitefish Bay are at least ___ thick in most winters, and thicknesses of _____ may be reached

4 ft, 8 to 9 ft

In the north part of Lake Superior, ice begins to form along the shore in ____ and ____

Late January, early December

Significant fast ice develops only in

Nipigon Bay and Black Bay

After reaching a thickness of ____ , the fast ice along the northern shore breaks up by ____

30 to 35 inches, mid-April

In the west end of Lake Superior, fast ice about ______ thick builds ___ from Duluth as far as the Apostle Islands

4 to 6 inches, northeast

The lake may briefly become covered in ice ______ percent, but the strong winds and the associated winds reduce the ice coverage greatly

80 to 90

Local magnetic disturbances are more prevalent in ____ than the other Great Lakes

Lake Superior

Reports from vessel masters show that the strongest disturbances are along the ____ shore of the Lake, that they decrease in intensity as the distance from this shore increases, and that the tendence is for ____ vessels to be drawn towards the ____ shore

north, upbound, north

Downbound vessels from Duluth Ship Canal shall pass not less than ____ off Devils Island Light

12 miles

Downbound vessels shall pass not less than ____ off Eagle Harbor Light

12 miles

Downbound vessels shall pass not less than ____ off Copper Harbor Light

12 miles

Downbound vessels shall pass not less than ____ off Manitou Light

12 miles

Downbound vessels shall pass not less than ___ off Whitefish Pt Light

2.5 miles

Downbound vessels from Two Harbors shall pass not less than ____ off Devils Island

12 miles

Downbound vessels from Taconite Harbor shall pass not less than _____ north of Eagle Harbor

12 miles

Downbound vessels from Marquette shall pass not less than ____ off Au Sable Light

7 miles

Downbound vessels from Marquette shall pass not less than ____ off the abandoned lighthouse at Crisp Pt

7 miles

Downbound vessels from Thunder Bay shall pass not less than ____ from Thunder Cape

2.5 miles

From Mission River entrance, downbound vessels shall pass not less than ____ from Thunder Cape

2.5 miles

Downbound vessels shall pass not less than ___ from Towbridge Island Light

1.75 miles

Downbound vessels shall pass not more than ____ off Blake Point Light abeam

2.5 miles

Downbound vessels shall pass not less than ___ from Passage Island Light

1 mile

Downbound vessels shall pass not less than ____ from Whitefish Pt

2.5 miles

Upbound vessels shall transit to a point no more than ____ off the abandoned lighthouse in Crisp Pt

4.5 miles

Upbound vessels shall pass not more than ____ off Manitou Light

4 miles

Upbound vessels shall pass not more than ____ off Copper Harbor Light

5 miles

Upbound vessels shall pass not more than ___ off Eagle Harbor Light

5 miles

Upbound vessels shall pass not more than ___ off Devils Island Light

5 miles

Upbound vessels for Marquette shall pass not more than ____ off Au Sable Light

4.5 miles

Upbound vessels for Thunder Bay shall pass not more than ___ from Trowbridge Island Light

0.75 miles

Upbound vessels for Thunder Bay shall pass not more than ____ off Thunder Cape

1 mile

Upbound vessels for Thunder Bay shall pass not more than ___ off Hare Island Reef Lighted Buoy A2

0.5 mile

Upbound vessels for Thunder Bay shall pass not less than ____ from Welcome Island Light

1.25 miles

Pt Iroquois is marked by what on the SE side of the bay on the west side of the entrance to St. Marys River

An abandoned lighthouse

What is 2.2 miles west of Pt Iroquois

Nodoway Pt

What is a prominent 400 ft hill between Pt Iroquois and Nodoway Pt

Mission Hill

Where is Tahquamenon Bay located?

The southwest part of Whitefish Bay

What makes Whitefish Point a poor radar target?

It has sandhills and some trees

What structure is shown from Whitefish Pt Light

A white cylindrical tower with a Racon

What are good landmarks at Vermilion Pt

The abandoned Coast Guard Station

What are some characteristics of Little Lake Harbor

The only harbor of refuge between Whitefish Pt and Grand Marais, is surrounded by a small oval lake (Little Lake) with depths of 18 ft and more with good water close to shore

What are the anchorage conditions of West Bay

Good anchorage in depths of 18 to 40 feet with a sand bottom

Where is the large area of magnetic disturbance in relation to Au Sable Pt

40 miles NW

Tugs are available from Sault Ste. Marie and Duluth

True

What are some characteristics of Grand Island

A wooded island

Where is the Thumb located in relation to Grand Island

The SE part

Where are the submerged cables in relation to Grand Island Harbor

Between Powell Pt and the south end of Grand Island

What are some prominent features of Munising Harbor

Lighted radio masts on the high ground west of the town and the black stack and silver tank at Neenah Paper Company

What are some prominent features of Marquette Harbor

It receives coal and caustic soda. It also has two stacks at the Shiras Generating Plant. Its breakwater light is shown from a white cylindrical tower that has sound activationW by keying the microphone 5 times on VHF-FM channel 83A

What are the anchorage conditions of Marquette Harbor

Good anchorage, sometimes vessels anchor SW of the outer end of the breakwater. There’s a special anchorage at the north end of the harbor where the Harbormaster decides the location and length of time any watercraft may anchor in that area. Marquette is also a customs station.

Mooring is prohibited at the Marquette breakwater

True

What structure is shown from Presque Isle Harbor Breakwater Light

A white cylindrical tower with a red band on an octagonal building. Also has sound activation by keying the microphone 5 times on VHF-FM 83A

What is the purpose of the Marquette Harbor Breakwater Outer Light

It has a red sector from 181° to 198° warning vessels of the Presque Island Pt rocks

What is the purpose of Granite Island Light

It serves as a guide to vessels approaching Marquette Harbor from the north or west

Magnetic disturbances have been observed around Stannard Rock

True

What VHF channel does the harbormaster at Presque Isle Harbor monitor

Channel 9

What VHF channels does the harbormaster at Big Bay Harbor monitor

Channels 9 and 16

What is the structure coming from Huron Island Light

A gray granite tower on a dwelling on the NW part of the Huron Islands

Where is the deep water in Huron Bay

Within 0.5 mile of shore in the outer part, and the shores become deep-to in the inner part

Where is Pt Abbaye located

The point at the outer end of the peninsula separating the west side of Huron Bay from Keweenaw Bay

Where is Huron Bay Light

The SE side of Huron Bay roughly 6 miles SW of Pt Abbaye

What are the dimensions of Keweenaw Bay

12 miles wide at the entrance with a minimum width of 1.1 miles abreast Sand Point. The east shore of the bay has deep water within 0.4 mile and the west shore within 0.7 mile

What is the length of the Keweenaw Waterway

25 miles