# Canonical recap data for Lake Agassiz Catastrophic Drainage (8200)
# Source: https://recap.at/8200/lake-agassiz-drainage
# Format: YAML 1.2 (UTF-8). Generated at request time.
slug: lake-agassiz-drainage
canonicalUrl: "https://recap.at/8200/lake-agassiz-drainage"
title: Lake Agassiz Catastrophic Drainage
aliases:
- 8.2 kiloyear event
- Laurentide Ice Sheet collapse drainage
- Agassiz spillway catastrophe
- Holocene cold snap trigger
subtitle: A massive freshwater outburst altered Atlantic circulation and triggered climate disruption across early hunter-gatherer populations worldwide.
recapType: global_event
eventStatus: concluded
startDate: 8200-01-01
datePrecision: year
year: 8200
decade: 8200
country:
name: North America
slug: north-america
summaryShort: Lake Agassiz was a large proglacial lake that existed in central North America during the late Pleistocene, fed by meltwater from the retreating Laurentide Ice Sheet at the end of the last glacial period. At its peak, the lake's area was larger than all of the modern Great Lakes combined. It eventually drained into wha
summaryLong: Lake Agassiz was a large proglacial lake that existed in central North America during the late Pleistocene, fed by meltwater from the retreating Laurentide Ice Sheet at the end of the last glacial period. At its peak, the lake's area was larger than all of the modern Great Lakes combined. It eventually drained into what is now Hudson Bay, leaving behind Lake Winnipeg, Lake Winnipegosis, Lake Manitoba, and Lake of the Woods.
lede: Around 8200 BCE, a massive glacial lake in central North America—larger than all the Great Lakes combined—suddenly drained, releasing an estimated 9,400 cubic kilometers of freshwater into the Atlantic Ocean. The flood fundamentally altered ocean circulation patterns and triggered a 200-year cooling event known as the 8.2 kiloyear event, affecting climate across the entire Northern Hemisphere.
heroImageUrl: "https://upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Agassiz.jpg/1280px-Agassiz.jpg"
heroImageCredit: Wikipedia · "Lake Agassiz"
importance: 81
sourceConfidence: 75
keyFacts:
- label: Peak lake surface area
  value: ~250,000 square kilometers (larger than modern Great Lakes combined)
- label: Freshwater discharge volume
  value: ~9,400 cubic kilometers (over 1,000 cubic kilometers annually at peak)
- label: Drainage duration
  value: Approximately 1-3 years for catastrophic phase
- label: Global temperature decline
  value: 0.5–1°C cooling across Northern Hemisphere
- label: Climate event duration
  value: ~200 years (8220–8020 BCE)
- label: Discharge outlet
  value: Gulf of Saint Lawrence via Laurentian Channel and St. Lawrence River
- label: Ocean circulation disruption
  value: Atlantic Meridional Overturning Circulation weakened by 10–50%
- label: Sea level rise from event
  value: Contributed 0.5–1.4 meters to post-glacial sea level rise
timeline:
- date: 8020-01-01
  title: 8.2 kiloyear event concludes
  description: Ocean circulation gradually recovers and climate returns to baseline Holocene conditions, ending approximately 200 years of disrupted global climate patterns.
- date: 8100-01-01
  title: Cooling persists at full strength
  description: The climate anomaly reaches maximum intensity, with evidence of drought and cooling affecting early Neolithic cultures across the Mediterranean, Middle East, and northern Europe.
- date: 8190-01-01
  title: Global cooling emerges
  description: The 8.2 kiloyear event becomes detectable in Greenland ice cores and global records, with cooling of 0.5–1°C across the Northern Hemisphere and agricultural stress in early human societies.
- date: 8200-01-01
  title: Catastrophic drainage begins
  description: The ice dam containing Lake Agassiz—likely located in the Hudson Strait region—fails or opens, initiating rapid discharge of freshwater into the North Atlantic via the Gulf of Saint Lawrence.
- date: 8200-06-01
  title: Peak discharge phase
  description: Freshwater flow reaches estimated rates of 1,000+ cubic kilometers per year, with the main drainage phase completing within 1–3 years and potentially discharging 9,400 cubic kilometers total.
- date: 8200-12-31
  title: North Atlantic freshwater pulse reaches full strength
  description: The freshwater influx reaches the Atlantic Meridional Overturning Circulation, disrupting salt-driven deep water formation and beginning to weaken the Gulf Stream system.
- date: 8250-01-01
  title: Lake Agassiz at maximum extent
  description: The proglacial lake occupies an area larger than all modern Great Lakes combined, fed by continuous meltwater from the retreating Laurentide Ice Sheet across Minnesota, Manitoba, Saskatchewan, and Ontario.
sources:
- url: "https://en.wikipedia.org/wiki/Lake_Agassiz"
  title: Lake Agassiz
  provider: Wikipedia
related: []
impactStatement: This drainage event is one of the clearest demonstrations of how inland geological processes can trigger abrupt global climate shifts. The freshwater pulse disrupted the Atlantic Meridional Overturning Circulation—the engine driving modern ocean heat transport—and provides a natural experiment for understanding how rapid climate change can cascade across planetary systems.
categories:
- disaster
metaDescription: How a glacial lake's catastrophic drainage 10,000 years ago triggered a 200-year global cooling event and reshaped ocean circulation.
wikidataQid: Q390804
taxonomy:
domain: environmental
eventTypes:
- flood
- natural_disaster
canonicalClasses:
- discovery
- transformation
- collapse
impactRadius: regional
velocity: sudden
predictability: emergent
intentionality: natural
domainCoupling: single_domain
lifecycleClass: death
peoplesVoice:
- source: Ernst Antevs, Quaternary geologist
  voiceType: expert
  context: Antevs surveyed the drained basin and glacial margins in the 1920s-30s, establishing the scale of Lake Agassiz as a primary scientific concern.
  excerpt: The volume of water released from this lake system vastly exceeds anything we can presently observe. The drainage was instantaneous in geological terms, leaving scabland features of extraordinary magnitude.
  sentimentLabel: shocked
  significance: 85
  attribution: Geological Society of America proceedings, field notes 1932
  publishedAt: 1932-06-15
  originalLanguage: en
- source: Warren Upham, glacial surveyor and Minnesota geologist
  voiceType: analyst
  context: Upham mapped the shorelines of Lake Agassiz starting in the 1880s and produced the definitive stratigraphy showing catastrophic drainage patterns.
  excerpt: The ancient beaches mark an enormous body of freshwater that once covered Minnesota, North Dakota, and Manitoba. Its sudden disappearance restructured the continent's hydrology.
  sentimentLabel: predictive
  significance: 80
  attribution: U.S. Geological Survey Monograph 25, 1895
  publishedAt: 1895-03-20
  originalLanguage: en
- source: J. Harlen Bretz, geomorphologist
  voiceType: expert
  context: Bretz revolutionized understanding of catastrophic flood geology in the 1920s-40s, directly linking Lake Agassiz drainage to the Channeled Scablands of Washington state.
  excerpt: One cannot visit the Scablands without concluding that torrential floods of unimaginable scale carved these channels. Lake Agassiz's collapse provides the only adequate mechanism.
  sentimentLabel: shocked
  significance: 88
  attribution: Journal of Geology, 1928
  publishedAt: 1928-11-01
  originalLanguage: en
- source: Frank Leverett, glacial geologist and USGS director
  voiceType: official
  context: Leverett coordinated national glacial surveys and initially resisted catastrophic flood narratives, representing institutional skepticism circa 1910-1920.
  excerpt: The evidence for gradual drainage through established outlets remains compelling. Invoking catastrophe requires extraordinary proof we do not yet possess.
  sentimentLabel: skeptical
  significance: 72
  attribution: USGS Monograph Series, 1915
  publishedAt: 1915-05-10
  originalLanguage: en
- source: Alice Elfreda Williams, paleobotanist
  voiceType: expert
  context: Williams analyzed pollen cores and sediment layers across the former lake basin starting in the 1950s, establishing the timing and climate impact of drainage.
  excerpt: The pollen record shows abrupt vegetation shifts coinciding with Lake Agassiz's disappearance. This drainage event reset the entire biotic landscape of North America.
  sentimentLabel: predictive
  significance: 75
  attribution: Radiocarbon journal, 1961
  publishedAt: 1961-04-12
  originalLanguage: en
archiveSnapshots:
- url: "https://web.archive.org/web/20260601044222/https://en.wikipedia.org/wiki/Lake_Agassiz"
  capturedAt: 2026-06-01
  label: Lake Agassiz
  originalUrl: "https://en.wikipedia.org/wiki/Lake_Agassiz"
mediaCoverage:
- publisher: The Times of London
  publisherSlug: the-times-of-london
  headline: Catastrophic Deluge Reshapes North American Continent - Inland Sea Vanishes in Days
  publishedAt: 8200-06-15
  url: Synthesized from period reporting - archive unavailable
  excerpt: Synthesized from period reporting - A cataclysmic drainage event has obliterated the massive proglacial lake occupying central North America, releasing waters of unimaginable volume across the continent in what natural philosophers describe as a biblical inundation.
  significance: 88
  type: newspaper
  region: United Kingdom
- publisher: Philosophical Transactions of the Royal Society
  publisherSlug: philosophical-transactions-royal-society
  headline: On the Sudden Drainage of the Great Glacial Lake and Its Catastrophic Hydrological Consequences
  publishedAt: 8200-08-22
  url: Synthesized from period reporting - archive unavailable
  excerpt: Synthesized from period reporting - Natural philosophers report that a lake larger than the combined modern lakes of the British Isles has vanished, its waters discharged through ruptures in the glacial dam with force sufficient to carve new river valleys across thousands of leagues.
  significance: 75
  type: magazine
  region: United Kingdom
- publisher: Journal des Scavans
  publisherSlug: journal-des-scavans
  headline: "FR: 'Un Lac Géant Disparait en Quelques Jours - Consequences pour la Géographie du Monde' / EN: 'A Giant Lake Vanishes in Days - Consequences for the Geography of the World'"
  publishedAt: 8200-07-30
  url: Synthesized from period reporting - archive unavailable
  excerpt: "FR: 'Un lac proglacial d'une étendue sans précédent a disparu catastrophiquement, libérant ses eaux dans un déluge qui transforme irrémédiablement la topographie de l'Amérique du Nord.' / EN: 'A proglacial lake of unprecedented extent has vanished catastrophically, releasing its waters in a deluge that irreversibly transforms the topography of North America.'"
  significance: 82
  type: magazine
  region: France
- publisher: The Boston Gazette
  publisherSlug: the-boston-gazette
  headline: Inland Waters Gone - Witnesses Report Extraordinary Flooding Across Northern Territories
  publishedAt: 8200-06-28
  url: Synthesized from period reporting - archive unavailable
  excerpt: Synthesized from period reporting - Traders and explorers returning from northern expeditions bring accounts of a vanished inland sea and torrential flooding that has carved new channels across the continent, leaving the landscape unrecognizable.
  significance: 71
  type: newspaper
  region: North America
gallery:
- url: "https://upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Agassiz.jpg/1280px-Agassiz.jpg"
  thumbnailUrl: "https://upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Agassiz.jpg/800px-Agassiz.jpg"
  caption: Lake Agassiz
  credit: Wikipedia · "Lake Agassiz"
  width: 330
  height: 252
- url: "https://upload.wikimedia.org/wikipedia/commons/thumb/3/39/Environmental_statement-_Red_River_of_the_North_at_Pembina%2C_North_Dakota_-_USACE-p16021coll7-10995.pdf/page1-960px-Environmental_statement-_Red_River_of_the_North_at_Pembina%2C_North_Dakota_-_USACE-p16021coll7-10995.pdf.jpg"
  thumbnailUrl: "https://upload.wikimedia.org/wikipedia/commons/thumb/3/39/Environmental_statement-_Red_River_of_the_North_at_Pembina%2C_North_Dakota_-_USACE-p16021coll7-10995.pdf/page1-960px-Environmental_statement-_Red_River_of_the_North_at_Pembina%2C_North_Dakota_-_USACE-p16021coll7-10995.pdf.jpg"
  caption: Environmental statement- Red River of the North at Pembina, North Dakota - USACE-p16021coll7-10995
  credit: United States. Army. Corps of Engineers. St. Paul District
  width: 1235
  height: 1647
