Exploding Lakes Explained: Limnic Eruptions, Carbon Dioxide and Deadly Gas Clouds

A lake can look perfectly calm while storing a lethal quantity of gas beneath its surface.

In a small number of deep lakes, carbon dioxide enters the bottom water through volcanic
springs, groundwater and deep geological pathways. In other lakes, microorganisms generate
methane as organic matter decomposes in oxygen-free water and sediment.

If the lake remains permanently stratified, its deep water may stay isolated from wind and
the atmosphere. Gas continues accumulating under pressure instead of escaping gradually.

The system behaves somewhat like a sealed carbonated drink. While the water remains deep and
pressurized, much of the gas stays dissolved. If gas-rich water is lifted toward the surface,
pressure decreases and bubbles begin to form.

Those bubbles reduce the density of the water. The bubbly water rises faster, experiences
still lower pressure and releases even more gas. Under the wrong conditions, this positive
feedback becomes a runaway process called a limnic eruption.

The resulting event may send a fountain of water and gas above the lake, generate waves and
release an invisible carbon-dioxide cloud. Because carbon dioxide is denser than ordinary air,
it can travel downhill and accumulate in low-lying valleys.

The best-known disasters occurred at Lake Monoun in 1984 and Lake Nyos in 1986, both in
Cameroon. These events transformed limnic eruptions from a theoretical possibility into a
recognized natural hazard.

What Is an Exploding Lake?

An exploding lake is an informal name for a lake capable of releasing a large volume
of dissolved gas during a limnic eruption.

The term does not mean that the entire lake detonates. The dramatic event is a rapid
transition from gas dissolved invisibly in water to free bubbles and atmospheric gas.

What may be released?

Gas-rich lakes may contain:

• Carbon dioxide
• Methane
• Hydrogen sulfide
• Nitrogen
• Smaller quantities of other dissolved gases

Carbon dioxide was responsible for the known fatal limnic eruptions in Cameroon.
Lake Kivu contains both carbon dioxide and large quantities of methane.

Why the surface can look normal

Most of the dangerous gas is stored hundreds of meters below the surface.
The upper layer may remain oxygenated, biologically active and visually ordinary.

Why only certain lakes are vulnerable

A dangerous lake generally needs a combination of depth, continuous gas input,
strong stratification and limited deep-water mixing.

What Is a Limnic Eruption?

A limnic eruption is a rapid release of dissolved gas from lake water.
The word limnic refers to freshwater systems and lakes.

The process may also be described as:

• Lake overturn
• Lake degassing
• Gas burst
• Lake gas eruption
• Catastrophic lake exsolution

Is a limnic eruption volcanic?

The gas may ultimately come from magma or deep volcanic systems, but the eruption itself
occurs within the lake water.

No new magma needs to reach the lake during the event.

Is it an explosion?

Rapid bubble expansion and rising water can be violent, but the primary process is not
chemical combustion.

The danger comes from sudden gas release, water displacement, waves and oxygen displacement
in the surrounding air.

Conditions Required for a Limnic Eruption

Limnic eruptions are extremely rare because several unusual conditions must occur together.

A deep lake

Pressure increases with water depth. Deep water can therefore hold more dissolved gas
than shallow water.

Persistent gas input

Carbon dioxide or methane must enter or form within the lake faster than it escapes.

Strong density stratification

The deep water must remain denser than the surface water, preventing ordinary seasonal
mixing from ventilating it.

Limited wind mixing

Sheltered volcanic craters and steep-sided basins reduce the ability of wind to stir
the entire water column.

Long residence time

Deep water must remain isolated long enough for gas concentrations to increase.

Approach to saturation

The dissolved-gas concentration must become high enough that lifting the water toward
lower pressure causes substantial bubbling.

A disturbance or instability

Some process must begin moving gas-rich water upward or weaken the lake’s density barrier.

Where Does the Gas in an Exploding Lake Come From?

Lake gas may be geological, biological or a mixture of both.

Volcanic carbon dioxide

Magma and hot rock release carbon dioxide through fractures beneath volcanic regions.
The gas dissolves into groundwater before entering the lake through springs or the lakebed.

Deep geological fluids

Carbon dioxide can rise from deep crustal sources even when no visible volcanic eruption
is occurring.

Organic decomposition

Microorganisms break down sinking organic matter in oxygen-poor water and sediment.
This process produces carbon dioxide.

Methanogenesis

In strongly reducing conditions, methane-producing microorganisms convert carbon compounds,
hydrogen and carbon dioxide into methane.

Thermal alteration

Heat and water-rock reactions may also release gases from deep sedimentary or volcanic material.

Groundwater transport

Gas dissolved under pressure in groundwater may enter the deepest part of a lake without
producing obvious bubbles at the surface.

Carbon Dioxide in Deep Lakes

Carbon dioxide dissolves readily in water, especially under high pressure.

Some of the dissolved carbon dioxide reacts with water to form carbonic acid,
bicarbonate and carbonate species.

Why deep water stores more carbon dioxide

Hydrostatic pressure increases with depth. Higher pressure keeps a larger proportion
of carbon dioxide dissolved.

Why cold water matters

Gas solubility generally increases as water becomes colder.
Deep tropical lakes may maintain cool, stable bottom layers despite warm surface conditions.

Why carbon dioxide may not bubble immediately

As long as dissolved-gas concentration remains below saturation at the local pressure,
the gas can remain invisible within the water.

Carbonic acid and lake chemistry

Dissolved carbon dioxide lowers pH and changes alkalinity, mineral solubility and microbial activity.

Continuous recharge

If volcanic or geological carbon dioxide continues entering the lake, gas concentration
can slowly recover even after artificial degassing.

Methane in Gas-Rich Lakes

Methane creates a different but overlapping hazard.

It can form biologically in oxygen-free deep water and sediment, where microorganisms
decompose organic matter.

Methane is buoyant and combustible

Methane is lighter than air and can burn when mixed with oxygen within a suitable concentration range.

Methane versus carbon dioxide

Carbon dioxide does not burn but can form a dense, suffocating cloud.
Methane can displace oxygen and may ignite if an ignition source is present.

Microbial conversion of carbon dioxide

In some lakes, microorganisms convert part of the carbon dioxide and hydrogen into methane.

Gas hydrates

Under sufficiently high pressure and low temperature, methane may be incorporated into
ice-like gas-hydrate structures, although dissolved gas is the dominant concern in known
African gas-rich lakes.

Energy resource

Methane can be extracted and used for electricity generation, turning a natural hazard
into an energy source if the lake is managed carefully.

Permanent Stratification and Meromictic Lakes

Many ordinary lakes mix from surface to bottom during seasonal cooling.
Gas-rich exploding lakes generally do not.

Lakes whose deepest waters remain isolated are called meromictic lakes.

The mixolimnion

The upper layer mixes with wind and seasonal temperature changes.
It exchanges oxygen and gases with the atmosphere.

The monimolimnion

The deep, dense layer remains largely isolated.
It may contain little oxygen and large quantities of dissolved carbon dioxide, methane
or hydrogen sulfide.

The chemocline

A strong chemical and density boundary separates the upper and lower waters.

Why deep water is denser

Deep water may contain more dissolved salts, minerals and gases.
Geothermal input and groundwater chemistry can reinforce this density difference.

Why wind cannot mix the whole lake

Wind energy is often insufficient to overcome the strong density gradient,
especially in deep crater lakes surrounded by steep walls.

For a broader explanation, see

Permanently Stratified Lakes
.

Pressure, Depth and Gas Solubility

The physics of an exploding lake begins with the relationship between pressure and gas solubility.

Henry’s law

At a given temperature, the quantity of gas dissolved in water generally increases with
the partial pressure of that gas.

Hydrostatic pressure

Every meter of overlying water adds pressure.
Gas-rich water at the bottom of a deep lake can therefore remain stable at concentrations
that would bubble violently near the surface.

Exsolution

When pressure falls, dissolved gas separates from the liquid and forms bubbles.
This process is called exsolution.

Nucleation

Bubbles form more easily on particles, existing gas pockets, sediment grains and rough surfaces.

Bubble expansion

Rising bubbles expand as surrounding pressure decreases.
The expanding gas displaces more water and increases upward flow.

The carbonated-drink analogy

Opening a carbonated bottle reduces pressure and allows dissolved carbon dioxide to form bubbles.
A limnic eruption is much larger and more complex, but the pressure-release principle is similar.

How Runaway Degassing Begins

A catastrophic release develops through positive feedback.

Stage 1: Gas-rich water is displaced upward

A disturbance moves deep water toward a shallower level.

Stage 2: Pressure decreases

The rising water can no longer hold the same quantity of dissolved gas.

Stage 3: Bubbles form

Carbon dioxide or methane comes out of solution.

Stage 4: Water density falls

Bubbly water is less dense than surrounding bubble-free water.

Stage 5: Upward acceleration increases

The buoyant mixture rises faster, carrying more deep water toward the surface.

Stage 6: More gas exsolves

Continued pressure loss releases additional gas.

Stage 7: A gas-and-water fountain develops

Rapid flow may disturb the lake surface, produce a plume and generate waves.

Stage 8: Atmospheric gas spreads outward

Carbon dioxide flows over the lake rim and descends into surrounding valleys.

Why the process can stop

Degassing slows when the most unstable gas-rich water has been released,
when mixing dilutes the remaining gas or when the upward flow loses momentum.

What Can Trigger a Limnic Eruption?

The exact trigger for a past event may remain uncertain even when the overall gas-release
mechanism is clear.

Landslides

Rock, soil or sediment entering the lake can displace deep water and generate internal waves.

Earthquakes

Seismic shaking may disturb lake layers, trigger slope failure or release gas from sediment.

Volcanic activity

New gas input, heating, deformation or an underwater eruption could destabilize the water column.

Strong cooling

Unusually cool surface water becomes denser and may sink, deepening seasonal circulation.

Intense storms

Wind, rainfall and inflowing floods may create internal waves or change density relationships.

Subaqueous sediment failure

Sediment slumps on the lake floor can displace gas-rich bottom water.

Internal waves

Waves moving along the boundary between layers can lift deep water without producing
obvious surface waves.

Gas saturation itself

If deep water reaches or approaches saturation, a small disturbance may be sufficient
to initiate bubbling.

Human activity

Poorly designed drilling, pumping, gas extraction or water discharge could disturb
a strongly stratified lake.

The 1984 Lake Monoun Disaster

Lake Monoun is a volcanic maar lake in Cameroon.
On August 15, 1984, a sudden gas release killed 37 people near the lake.

The victims were found along a low-lying road and surrounding terrain.
Vehicles had stopped, yet there was little evidence of fire, major trauma or an ordinary explosion.

Initial confusion

Possible explanations included poisoning, terrorism, volcanic gas and other unusual causes.

Carbon dioxide explanation

Investigation showed that a dense cloud of carbon dioxide had escaped from the lake
and displaced breathable air.

Why the event mattered

Lake Monoun provided the first modern warning that deep volcanic lakes could suddenly
release lethal gas.

Connection with Lake Nyos

When a much larger disaster occurred at Lake Nyos two years later, the similarities
helped scientists recognize a distinct natural-hazard mechanism.

Degassing

Controlled degassing pipes were later installed to reduce the carbon-dioxide inventory
in the deep water.

The 1986 Lake Nyos Disaster

Lake Nyos is a deep volcanic crater lake in northwestern Cameroon.
On the night of August 21, 1986, it released a massive quantity of carbon dioxide.

The gas flowed out of the crater and through surrounding valleys, suffocating approximately
1,700 people as well as thousands of cattle and wild animals.

A silent disaster

Many victims were sleeping. Carbon dioxide is colorless and, at dangerous concentrations,
provides little useful sensory warning.

Lake disturbance

Witnesses and post-event observations indicated violent disturbance of the lake,
vegetation damage near the shoreline and a large gas release.

Why villages far from the shore were affected

Dense carbon dioxide followed topography and traveled through valleys beyond the immediate
lake basin.

Cause of death

The gas displaced oxygen and interfered with breathing.
Survivors reported loss of consciousness, weakness, confusion and respiratory symptoms.

Was it a volcanic eruption?

The carbon dioxide had a deep geological or magmatic origin, but evidence favored catastrophic
release from gas-charged lake water rather than a conventional magma eruption on that night.

Long-term response

Scientists monitored gas recharge and installed controlled degassing systems to reduce
the possibility of recurrence.

Why Carbon Dioxide Clouds Are Deadly

Carbon dioxide is a normal component of the atmosphere and a product of respiration,
but high concentrations are extremely dangerous.

Oxygen displacement

A concentrated carbon-dioxide cloud reduces the proportion of breathable oxygen.

Physiological effects

High carbon-dioxide exposure can cause:

• Rapid breathing
• Headache
• Dizziness
• Confusion
• Loss of coordination
• Loss of consciousness
• Respiratory failure
• Death

Hypercapnia

Carbon dioxide entering the bloodstream raises carbonic acid and disrupts normal blood chemistry.

No flame or smoke

Unlike fire, carbon-dioxide exposure may occur without heat, visible smoke or burning odor.

Animals as indicators

Dead insects, birds, livestock or wildlife in low areas may indicate a dangerous gas accumulation,
but people should not enter the area to investigate.

How a Limnic-Eruption Gas Cloud Moves

Carbon dioxide is denser than ordinary air under comparable conditions.

Gravity flow

A concentrated cloud can spill over a crater rim and descend like an invisible fluid.

Valley channeling

Ravines and valleys guide the gas away from the lake and may concentrate it.

Low-area accumulation

Depressions, basements, pits and enclosed rooms can trap carbon dioxide.

Wind effects

Strong wind promotes dilution and dispersal, while calm nighttime conditions allow
the dense cloud to remain concentrated near the ground.

Topographic protection

Elevated ridges may remain above the densest part of the cloud, although turbulent mixing
makes exact boundaries unpredictable.

Why running downhill is dangerous

Moving into lower terrain may lead directly into greater gas concentrations.

Lake Kivu and Its Methane-Rich Deep Water

Lake Kivu lies between Rwanda and the Democratic Republic of the Congo within the
tectonically and volcanically active East African Rift.

It is far larger than lakes Nyos and Monoun and contains substantial quantities of
dissolved carbon dioxide and methane in its permanently stratified deep water.

Why Lake Kivu is unusual

Salinity and temperature gradients divide the lake into strongly separated layers.
The deepest waters contain high dissolved-gas concentrations and remain isolated from the surface.

Carbon dioxide input

Geological and volcanic sources deliver carbon dioxide through groundwater and deep springs.

Biological methane production

Microorganisms produce methane from organic matter and carbon compounds under oxygen-free conditions.

Large nearby populations

Cities and communities lie around Lake Kivu, increasing the consequences of any major destabilization.

Volcanic setting

The lake lies near active volcanic systems, including Nyiragongo and Nyamulagira.
Earthquakes, eruptions and underwater disturbances are therefore important considerations.

Is Lake Kivu about to explode?

The lake is monitored and remains stratified. Describing catastrophe as imminent without
evidence is misleading.

The legitimate concern is that its gas reservoir, large population and volcanic setting
require careful long-term management.

Could Other Lakes Undergo Limnic Eruptions?

Many lakes contain dissolved carbon dioxide or methane, but only a small subset combine
the conditions necessary for catastrophic accumulation.

Features scientists examine

• Great water depth
• Permanent stratification
• Volcanic or geothermal gas input
• High deep-water gas concentration
• Limited seasonal overturn
• Steep crater or basin walls
• Anoxic bottom water
• Increasing gas recharge

Volcanic crater lakes

Deep crater lakes in volcanic regions receive particular attention because geological
carbon dioxide may enter directly beneath them.

Reservoirs

Artificial reservoirs can also accumulate methane and carbon dioxide, especially in
tropical regions with abundant submerged organic matter.

Most reservoirs vent gas gradually, but deep-water withdrawal and dam operations require
appropriate gas-risk assessment.

Mine lakes

Deep mine pits may become stratified and accumulate dissolved gases, although human-created
mine lakes fall partly outside this natural-phenomena pillar.

Possible Warning Signs of Lake Degassing

A major limnic eruption may provide little warning, but unusual observations near a gas-rich
lake should be taken seriously.

Sudden bubbling

Widespread or rapidly increasing bubbling may indicate gas-rich water reaching lower pressure.

Water discoloration

Mixing can bring iron-rich, sulfur-rich or sediment-laden deep water to the surface.

Unusual waves

Surface disturbance without obvious wind may reflect internal water movement.

Dead fish or animals

Sudden mortality may indicate oxygen depletion, toxic gas or rapid chemical change.

Rotten-egg odor

Hydrogen sulfide may produce a rotten-egg smell at low concentrations.
Dangerous concentrations can impair smell, so odor is not a reliable safety test.

Dizziness or breathing difficulty

These symptoms near low ground require immediate movement to higher elevation and fresh air.

Instrumental warnings

Rising dissolved-gas concentrations, changing density layers, seismic activity and deformation
may provide more reliable warning than visual observations.

How Scientists Monitor Gas-Rich Lakes

Monitoring focuses on the amount of dissolved gas, the stability of lake layering and
possible geological disturbances.

Temperature profiles

Temperature measurements reveal thermal layers and changes in vertical stability.

Conductivity profiles

Conductivity indicates dissolved-ion concentrations and helps map density stratification.

Dissolved-gas sampling

Specialized samplers collect water at depth without allowing gas to escape before measurement.

Gas-pressure calculations

Scientists compare dissolved-gas concentration with saturation pressure at each depth.

pH and alkalinity

Carbon-dioxide input changes acidity and carbonate chemistry.

Dissolved oxygen

Oxygen profiles identify the transition between ventilated surface water and anoxic deep water.

Seismic monitoring

Instruments detect earthquakes, volcanic tremor, rockfalls and possible underwater landslides.

Lake-level monitoring

Water-level changes may affect pressure, dam stability and shoreline hazards.

Gas-flux measurements

Researchers measure carbon dioxide escaping through the lake surface and surrounding soil.

Remote sensing

Satellites and drones track surface color, temperature, landslides and changes around the basin.

Controlled Degassing of Exploding Lakes

Controlled degassing removes gas-rich deep water gradually before it can produce
a catastrophic release.

The goal

Engineers aim to reduce dissolved-gas concentration while preserving lake stratification
and avoiding sudden mixing.

Deep intake

A pipe extends from the surface to gas-rich bottom water.

Initial pumping

Water is first lifted mechanically until it reaches lower pressure and begins releasing bubbles.

Self-sustaining flow

Gas bubbles reduce the density of water inside the pipe.
The lighter mixture rises and draws additional deep water upward.

Surface release

Gas and water emerge from the pipe in a controlled fountain.
Carbon dioxide disperses into the atmosphere rather than accumulating catastrophically.

Long-term maintenance

If geological carbon dioxide continues entering the lake, some degassing capacity may
need to operate indefinitely.

How Self-Sustaining Degassing Pipes Work

Degassing pipes exploit the same physical feedback that makes a limnic eruption dangerous,
but confine it within engineered infrastructure.

1. Gas-rich water enters the lower end of the pipe.
2. Pumping lifts the water toward lower pressure.
3. Dissolved carbon dioxide forms bubbles.
4. The water-and-gas mixture becomes less dense.
5. Buoyancy accelerates the mixture upward.
6. The resulting flow draws more deep water into the pipe.
7. Gas escapes at the surface in a controlled location.

Why the pipe does not simply empty the lake

Degassed water returns to the lake surface while the main goal is gas removal,
not permanent water withdrawal.

Why pipe depth matters

The intake must reach the layer containing the targeted gas concentration without
unnecessarily mixing other layers.

Why flow must be monitored

Excessive or poorly designed withdrawal could alter density structure and create instability.

Methane Extraction and Power Generation

Lake Kivu’s dissolved methane can be used as an energy resource.

Deep-water extraction

Gas-rich water is pumped from a selected depth to processing equipment.

Pressure reduction

Lower pressure causes methane and carbon dioxide to separate from the water.

Gas separation

Methane is purified for use as fuel, while carbon dioxide and unwanted gases are managed separately.

Electricity generation

Extracted methane powers engines or turbines connected to electrical generators.

Reinjection

Processed water must be returned at a depth and density that do not destabilize the lake.

Potential benefit

Controlled extraction may reduce methane inventory while supplying energy.

Potential risk

Poorly managed extraction could disrupt stratification, mix nutrient-rich deep water upward
or alter gas distribution.

Landslides, Natural Dams and Secondary Hazards

Gas release is not the only hazard associated with steep-sided volcanic lakes.

Rockslides

Unstable crater walls may collapse into the water, generating waves and vertical mixing.

Natural dam failure

Some crater lakes are held behind weak volcanic or landslide material.
Erosion or structural failure can release catastrophic flooding.

Wave generation

Landslides, rapid degassing and rising gas-and-water fountains may create waves that
damage shorelines.

Erosion during degassing

Repeated surface discharge must be designed to prevent erosion around platforms and outlets.

Earthquake interaction

Seismic shaking can affect crater walls, pipes, shorelines and underwater sediment slopes.

Climate and the Stability of Gas-Rich Lakes

Lake stability depends partly on temperature, rainfall, evaporation and wind.

Surface warming

Warmer surface water may strengthen thermal stratification and reduce deep mixing.

Cooling events

Strong cooling makes surface water denser and can deepen circulation.

Rainfall and runoff

Freshwater input changes surface density and may strengthen or weaken stratification
depending on temperature and dissolved-mineral content.

Drought and falling lake levels

Lower water levels reduce pressure on deep gas-rich water, although the significance
depends on the scale of the change.

Extreme storms

Powerful wind and rainfall may disturb upper layers and trigger landslides.

Long-term interpretation

Climate change can alter lake mixing and hydrology, but specific hazard claims require
direct measurements of density structure and dissolved gas.

Limnic-Eruption Safety

People living near known gas-rich lakes require locally designed monitoring,
alarms, evacuation plans and public education.

Move uphill

Carbon dioxide tends to collect in low areas. Higher ground usually offers the best
immediate escape direction.

Do not enter valleys or depressions

Low terrain can channel and trap dense gas.

Leave enclosed spaces

Basements, pits, wells and poorly ventilated buildings may accumulate carbon dioxide.

Do not attempt a rescue without breathing equipment

Rescuers can lose consciousness within seconds in oxygen-deficient air.

Follow alarms immediately

Gas sensors and local warning systems may provide only a short evacuation window.

Approach from upwind and uphill

Emergency response should account for wind direction and terrain.

Do not rely on smell

Carbon dioxide is odorless, while hydrogen sulfide can disable the sense of smell.

Ventilate only after the area is declared safe

Entering a building to open windows may expose occupants to lethal gas.

Exploding-Lake Myths and Misconceptions

Myth 1: The lake explodes like a bomb

Misleading. A limnic eruption is rapid physical degassing rather than ordinary combustion.

Myth 2: Lava must enter the lake

False. Carbon dioxide may accumulate from deep volcanic sources for years without a surface eruption.

Myth 3: Carbon dioxide is harmless because people exhale it

False. Concentrated carbon dioxide can rapidly cause unconsciousness and death.

Myth 4: Victims are poisoned by toxic volcanic chemicals

In the documented Cameroonian disasters, oxygen displacement and high carbon-dioxide exposure
were the principal lethal mechanisms.

Myth 5: Gas-rich lakes visibly bubble all the time

False. High pressure can keep enormous quantities of gas dissolved invisibly at depth.

Myth 6: Every volcanic crater lake can explode

False. The lake also requires sufficient depth, gas input, stratification and deep-water isolation.

Myth 7: Lake Kivu will certainly erupt soon

Unsupported. Lake Kivu presents a serious long-term management issue, but claims of an
imminent event require direct evidence.

Myth 8: Degassing eliminates the problem forever

False. Continued geological gas input may require long-term monitoring and maintenance.

Myth 9: Running downhill is the best escape

False. Dense carbon dioxide follows low terrain, so moving uphill is generally safer.

Myth 10: A gas cloud can always be seen

False. Carbon dioxide itself is invisible, although water vapor, dust or disturbed vegetation
may sometimes reveal movement indirectly.

Why Study Exploding Lakes?

Exploding lakes connect volcanology, fluid physics, atmospheric hazards, microbiology
and disaster prevention.

• They reveal hidden volcanic degassing.
  Deep geological carbon dioxide can enter groundwater and lakes without visible eruptions.
• They demonstrate pressure-controlled gas storage.
  Deep water can hold quantities of gas impossible at the surface.
• They show how stratification creates hazards.
  Stable density layers can isolate gas for decades.
• They illustrate positive feedback.
  Bubble formation accelerates uplift and releases still more gas.
• They explain invisible topographic gas flows.
  Dense carbon dioxide can travel far beyond a lake through valleys.
• They demonstrate preventable natural disasters.
  Monitoring and controlled degassing can reduce risk.
• They provide potential energy resources.
  Methane extraction may supply electricity when carefully managed.

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