How Deep Is Lake Superior? Depth, Size and Shipwrecks

Quick answer: Lake Superior is 1,332 feet (406 meters) deep at its deepest point and 483 feet (147 meters) deep on average, according to the EPA and the National Park Service. NOAA’s Coast Pilot and NOAA’s ecosystem page list 1,333 feet instead. Both numbers describe the same lake, so name your source and move on.

Lake Superior depth: 1,332 or 1,333 feet?#

The EPA’s Lake Superior page lists an average depth of 483 feet, a maximum depth of 1,332 feet, a volume of 2,900 cubic miles and a water area of 31,700 square miles, all measured at low water. Pictured Rocks National Lakeshore repeats 483 feet and 1,332 feet (406 meters).

Other NOAA and NPS pages say 1,333 feet. NOAA’s Coast Pilot gives a “maximum recorded depth” of 1,333 feet, and NOAA’s ecosystem status page says the lake reaches 406 meters or 1,333 feet. Because 406 meters is about 1,332 feet, the two figures are essentially the same measurement written two ways. We found no source explaining which one is preferred, so we show both.

NOAA’s bathymetry page adds a caveat: Great Lakes depth data is a synthesis of soundings collected over more than a century by multiple agencies, and its Lake Superior contours are not complete, though a roughly 90-meter grid exists. So treat any single depth as the best published figure, not a perfect measurement.

Where is the deepest point?#

An NPS Isle Royale junior-ranger book says the deepest point of the Great Lakes lies in Lake Superior near Pictured Rocks National Lakeshore, 1,333 feet (406 meters) below the surface, and that if the Empire State Building stood there only its antenna would rise above the water. We did not find an official source with published coordinates, so we do not give any.

How big is Lake Superior?#

• Length and width: 350 miles long and 160 miles wide, per Pictured Rocks.
• Water area: 31,700 square miles. NPS calls it the largest body of fresh water in the world by surface area, while NOAA’s ecosystem page calls it the second largest lake in the world by surface area, so the ranking depends on how a source counts.
• Volume: 2,900 cubic miles. NPS calls it the third-largest lake in the world by volume and says it holds over half of the water in the Great Lakes. EPA’s table backs that up: the other four lakes add up to 2,539 cubic miles.
• Shoreline: the EPA says the shoreline and islands that rim the lake stretch 2,726 miles.
• Retention time: 191 years. The EPA defines this as a measure based on the lake’s volume and the mean rate of outflow, so it describes how slowly the lake turns over.
• Water volume in everyday terms: an NPS junior-ranger book says Superior holds three quadrillion gallons, about 10% of the world’s fresh surface water.

Superior next to the other Great Lakes#

From the EPA’s physical-features table, measured at low water:

For a lake-by-lake comparison, see our Great Lakes depth and volume guide, or look at how deep Lake Michigan is, Lake Erie and Lake Ontario. If you want a deep lake outside the Great Lakes, try how deep Crater Lake is.

How cold is Lake Superior, and why?#

NPS calls Superior the coldest Great Lake. Pictured Rocks gives an average temperature of 40°F, and the Apostle Islands page says the average annual water temperature is about 40°F. Sunny days can warm shallow water, though: the same Apostle Islands page says protected shallow bays can climb into the 70s on warm, calm summer days.

Isle Royale’s dive page gives a different view from the surface down: water at the surface rarely exceeds 55°F, and water below 50 feet is 34 to 37°F. It also warns that sunlight may not reach deeper depths in all conditions.

Cold is a real safety issue. Dress for the water, not the air, and read our Great Lakes swimming safety guide before you go in.

Does Lake Superior freeze over?#

Almost never completely. NOAA GLERL’s ice-cover record lists the annual maximum percentage of the lake covered in ice for each winter. For Lake Superior:

• It peaked at 100.0% in 1996 (March 8), and at 97.1% in 1979.
• It reached at least 95% in 7 of the 54 winters from 1973 to 2026: 1977, 1979, 1994, 1996, 2003, 2014 and 2015.
• It peaked at 95.8% in 2014 and 94.9% in 2019.
• The lowest peak in the record is 8.2% in 2012. Other low years include 2002 (10.3%), 1998 (11.1%) and 2024 (12.0%).
• The most recent winter in the record, 2026, peaked at 62.5% on March 2.

Our earlier version of this article said that 1979 was the last year the whole lake froze and that 2014 was the first full freeze in more than 20 years. The GLERL record does not support that, so we removed it. NOAA’s ecosystem page adds that over the last five years the trend in ice cover has been decreasing, within the 10th to 90th percentiles of the record.

How was Lake Superior formed?#

According to NPS, the lake sits on a rift that began splitting the North American continent about 1.1 billion years ago. At its peak the Midcontinent Rift was over 3,000 kilometers long and ran from at least Kansas up into Lake Superior and then down into Lower Michigan. Huge amounts of lava poured out and formed sequences thousands of feet thick, and those basalts are exposed only in the Lake Superior region.

The basin that holds the water is much younger than the rift. NPS says glaciers played an important role in shaping the Lake Superior basin, and that melting ice filled the basin that would become the lake. NPS’s Keweenaw page adds that the landscape there was mostly shaped over the past 2.5 million years by repeated glaciations. That is why a lake sitting on an ancient rift holds water from a recent ice age.

What is at the bottom of Lake Superior?#

Not sea monsters or alien bases. The earlier version of this guide repeated those jokes, and we removed them. What the sources do say:

• Cold, clear, nutrient-poor water. Pictured Rocks attributes Superior’s clarity to a low amount of organic material, and calls it oligotrophic, meaning nutrient poor. The surrounding forests and rock layers filter the water entering the lake and limit the phosphorus and other nutrients that algae and plants need.
• Shipwrecks. NPS says the lake has claimed 350 ships and only about half have been found. Isle Royale National Park is home to what the National Park Service calls its most intact collection of shipwrecks.
• Invasive fish. An EPA-hosted 2014 climate impacts report for the lake names ruffe, round goby and sea lamprey as invasive non-native fish, and says sea lamprey virtually eliminated lake trout in Lake Superior after arriving in the mid-1900s.

We found no source on the “39°F at the bottom” figure that earlier versions of this article used, so we do not repeat it. The sourced numbers above are the ones to trust.

The Edmund Fitzgerald#

The freighter Edmund Fitzgerald broke in two and sank in a severe storm on November 10, 1975. Michigan Sea Grant says it still sits on the bottom of Lake Superior at 530 feet, and a NOAA risk assessment from March 2013 also lists the wreck at 530 feet deep. That is deep, but only about 40% of the lake’s maximum depth.

At Isle Royale, portions of some wrecks lie less than 60 feet down, while many are far deeper, and NPS says deep dives require specific equipment and experience.

How big do the waves get?#

NPS says the tallest wave ever recorded on Lake Superior was 28.8 feet (8.77 meters). Pictured Rocks says the lake creates its own weather and acts like an inland sea. NPS also says it is classified as non-tidal, but it does experience seiches. Larger seiches can resemble storm surges that flood beaches and inundate boat docks, take about eight hours to cross the lake and come back, and can change nearshore water levels by as much as three feet or more.

A note on “Lake Inferior”#

An earlier version of this article described an underground “Lake Inferior” beneath Lake Superior. We searched NPS, EPA and NOAA sources and found no mention of it, so we removed that section. If you have a scientific source, tell us and we will review it.

Plan around the lake#

For a deeper look at the other Great Lakes, see how the Great Lakes were formed, why the Great Lakes are freshwater and our Great Lakes water levels guide.

Sources#

Checked on November 7, 2026: EPA Lake Superior, EPA physical features of the Great Lakes, Pictured Rocks National Lakeshore, NOAA Coast Pilot 6, NOAA ecosystem status for Lake Superior, EPA Lake Superior climate impacts report, NOAA NCEI bathymetry, NOAA GLERL annual maximum ice cover, NPS Apostle Islands swimming, NPS Isle Royale diving, NPS Isle Royale junior ranger book, NPS Midcontinent Rift, NPS Lake Superior geology, Michigan Sea Grant Edmund Fitzgerald, NOAA Edmund Fitzgerald risk assessment.

Frequently asked questions#