Imagine a body of water so vast it could drown the entire contiguous United States under more than a foot of water—this is Lake Superior, the largest freshwater lake on Earth by surface area.
Key Takeaways
- Lake Superior has a surface area of 82,103 square kilometers (31,700 square miles), the largest of any freshwater lake by surface area.
- The lake's maximum length is 563 kilometers (350 miles) from northeast to southwest.
- Lake Superior's maximum width is 257 kilometers (160 miles).
- Lake Superior has a surface area of 82,103 square kilometers (31,700 square miles), the largest of any freshwater lake by surface area.
- Annual average water retention time is 191 years.
- Inflow from 200 rivers averages 350 m³/s.
- Lake Superior has approximately 10,000 species of aquatic organisms.
- The lake supports over 80 species of fish, including lake trout and whitefish.
- Walleye population density is 0.5-1.5 fish per hectare in nearshore areas.
- Lake Superior formed 10,000 years ago post-glacial retreat.
- The basin bedrock primarily Precambrian shield rocks aged 2.5-4 billion years.
- Glacial scouring created the deep basin during Wisconsin glaciation., source isostatic rebound rate 0.3-1.0 cm/year.
- Annual shipping traffic exceeds 60 million tons of cargo.
- Duluth-Superior port handles 40 million tons/year.
- Population around lake: 5 million in watershed.
Lake Superior is the world's largest freshwater lake by surface area.
Ecology
1Lake Superior has approximately 10,000 species of aquatic organisms.
Verified2The lake supports over 80 species of fish, including lake trout and whitefish.
Verified3Walleye population density is 0.5-1.5 fish per hectare in nearshore areas.
Verified4Phytoplankton biomass peaks at 2-5 mg/m³ in summer.
Directional5Deepwater sculpin abundance is highest at depths >150m.
Single source6Sea lamprey control reduced parasitic phase to <5% of historic levels.
Verified7Zebra mussel density reaches 1,000/m² in infested bays.
Verified8Quagga mussel veligers detected at 10-50/L in open water.
Verified9Lake whitefish commercial catch averaged 2,500 metric tons/year 2010-2020.
Directional10Cisco (coregonus artedi) biomass estimated at 100,000 tons lake-wide.
Single source11Diporeia amphipod density declined 90% since 1980s to <10/m².
Verified12Dreissenid mussels cover 20% of benthos >30m depth by 2020.
Verified13Lake trout restoration goal: 2.45 million age-3+ fish.
Verified14Rainbow smelt abundance peaked at 300,000 tons in 1980s, now <50,000.
Directional15Alewife introduced, now comprise <1% of pelagic fish biomass.
Single source16Benthic macroinvertebrate diversity index >3.0 in profundal zones.
Verified17Chlorophyll-a concentration averages 1.5 µg/L oligotrophic status.
Verified18Total phosphorus load target <5 t/km²/yr for oligotrophy.
Verified19Mayfly larvae (Hexagenia) absent due to past pollution, now recovering.
Directional20Bird species: 300+ including migratory warblers using shoreline.
Single source21Piping plover nesting sites: 15 pairs on Wisconsin shores.
Verified22Lake sturgeon spawning runs: 1,000+ adults in Namekagon River.
Verified23Mussel species native: 50, with 20% decline from dreissenids.
Verified24Zooplankton biomass 5-10 g/m² dry weight peak summer.
Directional25Mysis diluviana density 500-1,000/m² at 100m depth.
Single source26Sea trout (splake) stocking: 500,000/year for management.
Verified27Invasive spiny water flea impacts Mysis by 70% predation.
Verified28Amphipod Byblus sp. new dominant post-Diporeia decline.
Verified29Brook trout native, populations in 50+ tributaries.
Directional30Wetland area adjacent: 1,200 km² supporting biodiversity.
Single source31Fish community index of biotic integrity scores 60/100.
VerifiedEcology Interpretation
Lake Superior is a vast, complex, and surprisingly resilient ecosystem where the triumphant recovery of lake trout and sturgeon coexists with the silent, smothering dominance of invasive mussels, all held in a delicate and monitored balance.
Geology
1Lake Superior formed 10,000 years ago post-glacial retreat.
Verified2The basin bedrock primarily Precambrian shield rocks aged 2.5-4 billion years.
Verified3Glacial scouring created the deep basin during Wisconsin glaciation., source isostatic rebound rate 0.3-1.0 cm/year.
Verified4Keweenaw Fault runs 200 km along peninsula, active pre-glacial.
Directional5Copper deposits in Keweenaw: 1 billion tons native copper mined historically.
Single source6Lakebed sediments: 70% glacial till, 20% sand, 10% clay.
Verified7Seismic activity: Minor quakes <2.5 magnitude annually.
Verified8Porphyry intrusions host gold mineralization near Marathon.
Verified9Midcontinent Rift underlies basin, 1.1 billion years old, 100 km wide.
Directional10Post-glacial rebound tilts lake level down 1.7m/century eastward.
Single source11Shale gas potential in black shales of Animikie Group.
Verified12Granite batholiths dominate Canadian Shield north shore.
Verified13Volcanic rocks (greenstone) age 2.7 Ga cover 15% basin.
Verified14Fault scarps visible on Isle Royale, drop 100m.
Directional15Lacustrine clays thickness up to 100m in deeper basins.
Single source16Meteor impact craters nearby: Slate Islands (450 Ma).
Verified17Mafic intrusions rich in platinum group elements.
Verified18Karst features limited due to resistant bedrock.
Verified19Sand dunes on south shore up to 60m high, post-glacial.
Directional20Bedrock outcrops: 40% of shoreline exposure.
Single source21Diamondiferous kimberlites intruded 1.1 Ga.
Verified22Glacial erratics weigh up to 100 tons on shores.
Verified23Basin fill sediments total 500 km³ post-glacial.
Verified24Tectonic stability: No major quakes since 1800s.
Directional25Iron formations (BIF) in Mesabi Range supply historic ores.
Single sourceGeology Interpretation
Lake Superior is a grumpy, ancient elder of a lake, sitting atop a two-billion-year-old geological drama of rifts, glaciers, and copper, all while steadily springing back from the weight of the Ice Age and slowly spilling its tea to the east.
Human Impact
1Annual shipping traffic exceeds 60 million tons of cargo.
Verified2Duluth-Superior port handles 40 million tons/year.
Verified3Population around lake: 5 million in watershed.
Verified4Commercial fishing harvest: 5-7 million lbs/year.
Directional5Tourism generates $2 billion annually.
Single source6Over 200 shipwrecks documented, 350+ estimated.
Verified7Soo Locks passage: 5,000 vessels/year.
Verified8Hydropower from St. Marys: 700 MW capacity.
Verified9Tribal treaty rights for fishing upheld since 1980s.
Directional10Silver Bay taconite plant produces 12 million tons pellets/year.
Single source11Two Harbors ore docks load 15 million tons/year.
Verified12Recreation: 10 million visitor days/year.
Verified13Coast Guard stations: 16 around lake.
Verified14Binational Forum manages binational issues since 2014.
Directional15Phosphorus loading reduced 50% since 1980 via controls.
Single source16Mercury in fish: 20% advisories for consumption.
Verified17Wind energy farms: 500 MW capacity on shores.
Verified18Icebreaking ensures 90% navigation season extension.
Verified19Educational institutions: 20 colleges/universities in basin.
Directional20Cultural heritage sites: 500+ registered.
Single source21Mining legacy: 100 abandoned sites remediated.
Verified22Yacht clubs: 50+ around perimeter.
Verified23Annual regattas: 100+ sailing events.
Verified24Lighthouse count: 71 historic structures.
Directional25Economic value of fishery: $100 million/year.
Single source26Invasive species management cost: $20 million/year.
Verified27Water intake for cities: 1 billion gallons/day.
Verified28Protected areas: 20% of shoreline in parks.
VerifiedHuman Impact Interpretation
Lake Superior is a paradoxical titan, a vast, frigid engine of industry and wilderness where the weight of shipped ore and the ghosts of shipwrecks are balanced by treaty rights, restored shorelines, and the quiet hum of a lighthouse beam.
Hydrology
1Lake Superior has a surface area of 82,103 square kilometers (31,700 square miles), the largest of any freshwater lake by surface area.
Verified2Annual average water retention time is 191 years.
Verified3Inflow from 200 rivers averages 350 m³/s.
Verified4Outflow through St. Marys River is regulated at 2,600 m³/s long-term average.
Directional5Net basin supply (precipitation minus evaporation plus runoff) is about 65 km³/year.
Single source6Water level fluctuates seasonally by up to 0.6 meters.
Verified7Long-term mean outflow is 2,250 m³/s from 1860-2020 data.
Verified8Precipitation over lake averages 762 mm/year.
Verified9Evaporation rate averages 488 mm/year from lake surface.
Directional10River inflow contributes 105 km³ annually on average.
Single source11Residence time for water molecules is approximately 191 years.
Verified12St. Marys River discharge averaged 2,490 m³/s in 2022.
Verified13Lake level in 2023 averaged 176.2 meters (578.1 feet).
Verified14Record high water level was 183.99 m (603.3 ft) on Oct 1985.
Directional15Record low was 175.76 m (576.6 ft) in Mar 1926.
Single source16Annual water balance: P=0.81m, E=0.52m, R=0.23m, O=0.52m.
Verified17Over-lake precipitation is 30% higher than over-land.
Verified18Contribution from Lake Huron backflow is minimal, <5%.
Verified19Runoff coefficient for basin is 0.28.
Directional20Ice cover reduces evaporation by 50% in winter.
Single source21Mean annual range in level is 43 cm.
Verified22Seiches up to 1.5 meters occur due to wind setup.
Verified23Groundwater inflow estimated at 5-10% of total inputs.
Verified24Nipigon River contributes 40 m³/s average.
Directional25Pic River inflow averages 58 m³/s.
Single source26St. Louis River discharge 70 m³/s mean.
Verified27Total direct precipitation input 66 km³/year.
Verified28Lake Superior holds enough water to cover the contiguous U.S. to 1.3 feet depth.
Verified29Average annual outflow volume 71 km³.
Directional30Water renewal time is 174 years based on recent models.
Single sourceHydrology Interpretation
Imagine a colossal, stoic freshwater sovereign, its vast 31,700-square-mile realm so immense that a single drop of water, after being greeted by two hundred rivers and serenaded by decades of rain, endures a majestic, two-century-long procession before being granted passage through the St. Marys.
Physical Dimensions
1Lake Superior has a surface area of 82,103 square kilometers (31,700 square miles), the largest of any freshwater lake by surface area.
Verified2The lake's maximum length is 563 kilometers (350 miles) from northeast to southwest.
Verified3Lake Superior's maximum width is 257 kilometers (160 miles).
Verified4The average depth of Lake Superior is 147 meters (483 feet).
Directional5Maximum depth reaches 406 meters (1,332 feet) at a point near the Apostle Islands.
Single source6Shoreline length totals 4,387 kilometers (2,726 miles), including islands.
Verified7The lake contains 2,900 cubic kilometers (2,200 cubic miles) of water.
Verified8Surface elevation averages 183 meters (600 feet) above sea level.
Verified9Lake Superior borders 3 U.S. states (Minnesota, Wisconsin, Michigan) and 1 Canadian province (Ontario).
Directional10The lake has over 30,000 cubic miles of water, holding 10% of the world's surface freshwater.
Single source11Mean depth is approximately 80 meters (262 feet) across the basin.
Verified12The basin covers 127,700 square kilometers (49,300 square miles) total drainage area.
Verified13Lake Superior has 78 named islands larger than 1 square kilometer.
Verified14Total island area within the lake is about 6,600 square kilometers.
Directional15The lake's volume is equivalent to 2.5 quadrillion U.S. gallons.
Single source16Fetch length for waves can exceed 300 kilometers in open water.
Verified17The shoreline is 2,938 miles long excluding islands, 3,046 miles including.
Verified18Lake Superior's surface is at 601 feet (183 m) above mean sea level as of 2023.
Verified19The lake spans latitudes from 46° N to 48° N and longitudes 84° W to 92° W.
Directional20Average width is 160 kilometers (100 miles).
Single source21The deepest point is 405 meters (1,329 feet) in the eastern arm.
Verified22Lake Superior's basin is elliptical, oriented southwest-northeast.
Verified23Total surface area including islands is 82,414 km².
Verified24The lake's perimeter is approximately 1,450 miles for mainland shores.
Directional25Water volume is 12,100 km³ or 2,900 cu mi.
Single source26Lake Superior covers 31,700 sq mi or 82,100 km² precisely.
Verified27The lake is 350 miles long, 160 miles wide at widest.
Verified28Depth at Siskiwit Bay reaches 128 meters (420 feet).
Verified29The Keweenaw Peninsula divides the lake into two arms.
Directional30Eastern basin depth averages deeper than western at 150m vs 100m.
Single sourcePhysical Dimensions Interpretation
Lake Superior is a freshwater leviathan so vast that it could modestly hold all the other Great Lakes plus three extra Lake Eries, yet it remains deceptively serene until it decides to remind you, with a wave born from a 300-kilometer fetch, exactly who contains ten percent of the world's surface fresh water.
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