Vog is a form of

air pollution Air pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. There are many different types ...

that results when

sulfur dioxide Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...

and other gases and particles emitted by an erupting

volcano A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates are ...

react with

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

and moisture in the presence of

sunlight Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when t ...

. The word is a

portmanteau A portmanteau word, or portmanteau (, ) is a blend of wordssmog Smog, or smoke fog, is a type of intense air pollution. The word "smog" was coined in the early 20th century, and is a portmanteau of the words ''smoke'' and '' fog'' to refer to smoky fog due to its opacity, and odor. The word was then inte ...

". The term is in common use in the

Hawaiian islands The Hawaiian Islands ( haw, Nā Mokupuni o Hawai‘i) are an archipelago of eight major islands, several atolls, and numerous smaller islets in the North Pacific Ocean, extending some from the island of Hawaii in the south to northernmost Kur ...

, where the

Kīlauea Kīlauea ( , ) is an active shield volcano in the Hawaiian Islands. Located along the southeastern shore of the Big Island of Hawaii, the volcano is between 210,000 and 280,000 years old and emerged above sea level about 100,000 years ago. Hi ...

volcano, on the

Island of Hawaii Hawaii ( ; haw, Hawaii ) is the largest island in the United States, located in the state of Hawaii. It is the southeasternmost of the Hawaiian Islands, a chain of volcanic islands in the North Pacific Ocean. With an area of , it has 63% of th ...

(the "Big Island"), erupted continuously between 1983 and 2018. Based in June 2008 measurements, Kīlauea emits 2,000–4,000 tons of sulfur dioxide (SO₂) every day.

Description

Vog is created when

volcanic gas Volcanic gases are gases given off by active (or, at times, by dormant) volcanoes. These include gases trapped in cavities (vesicles) in volcanic rocks, dissolved or dissociated gases in magma and lava, or gases emanating from lava, from volcanic ...

es (primarily oxides of

sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...

) react with sunlight,

and

moisture Moisture is the presence of a liquid, especially water, often in trace amounts. Small amounts of water may be found, for example, in the air (humidity), in foods, and in some commercial products. Moisture also refers to the amount of water vapo ...

. The result includes sulfuric acid and other sulfates. Vog is made up of a mixture of gases and aerosols which makes it hard to study and potentially more dangerous than either on their own. Vog, which originates from volcanic vents, differs from laze, created when lava enters the ocean.

Vog in Hawaii

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...

, the gas plumes of

rise up from three locations:

Halemaʻumaʻu Halemaumau (''six syllables: HAH-lay-MAH-oo-MAH-oo'') is a pit crater within the much larger Kīlauea Caldera at the summit of Kīlauea volcano on island of Hawaii (island), Hawaiʻi. The roughly circular crater was x before collapses that ...

Puʻu ʻŌʻō Puu Ōō (also spelled Pu‘u‘ō‘ō, and often written Puu Oo, , ) is a volcanic cone on the eastern rift zone of Kīlauea volcano in the Hawaiian Islands. The eruption that created Puu Ōō began on January 3, 1983, and continued nearly con ...

, and from along the coastline where lava flows from the East

Rift zone A rift zone is a feature of some volcanoes, especially shield volcanoes, in which a set of linear cracks (or rifts) develops in a volcanic edifice, typically forming into two or three well-defined regions along the flanks of the vent. Believed t ...

enter the ocean. The plumes create a blanket of vog that can envelop the island. Vog mostly affects the Kona coast on the west side of the Island of

, where the prevailing

trade wind The trade winds or easterlies are the permanent east-to-west prevailing winds that flow in the Earth's equatorial region. The trade winds blow mainly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisph ...

s blow the vog to the southwest and southern winds then blow it north up the Kohala coast. Prolonged periods of southerly Kona winds, however, can cause vog to affect the eastern side of the Island on rare occasions, and affect islands across the entire state as well."Vog: A Volcanic Hazard"
on USGS web site By the time the vog reaches other islands, the sulfur dioxide has largely dissipated, leaving behind ash, smoke, sulfates, and ammonia.

Comparing vog and smog

Vog and

smog Smog, or smoke fog, is a type of intense air pollution. The word "smog" was coined in the early 20th century, and is a portmanteau of the words ''smoke'' and '' fog'' to refer to smoky fog due to its opacity, and odor. The word was then inte ...

are different. Vog is formed when sulfur oxides emitted by a volcano react with moisture to form an

aerosol An aerosol is a suspension (chemistry), suspension of fine solid particles or liquid Drop (liquid), droplets in air or another gas. Aerosols can be natural or Human impact on the environment, anthropogenic. Examples of natural aerosols are fog o ...

. The aerosol scatters light, thus making the vog visible. Smog is formed largely from the incomplete

combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combusti ...

of fuel, reacting with

nitrogen oxides Nitrogen oxide may refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds: Charge-neutral *Nitric oxide (NO), nitrogen(II) oxide, or nitrogen monoxide *Nitrogen dioxide (), nitrogen(IV) oxide *Nitrogen trioxide (), or ni ...

and

ozone Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...

produced from

carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...

by reactions with sunlight. The result is also a visible aerosol. When smog levels are high, the sky appears yellowish-grey because nitrogen oxides are yellow. In contrast,

sulfur oxides Sulfur oxide refers to many types of sulfur and oxygen containing compounds such as SO, SO2, SO3, S7O2, S6O2, S2O2, etc. Sulfur oxide (SO''x'') refers to one or more of the following: * Lower sulfur oxides (S''n''O, S7O2 and S6O2) * Sulfur monox ...

are colorless and vog looks grey. Once the vog layer dissipates, grey spots of vog in the sky may, for a time, remain trapped in the inversion layer. Several chemicals emitted from cars are not emitted from volcanoes. Similarly, some chemicals emitted from volcanoes, such as

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...

hydrogen chloride The compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colourless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hydrogen chloride ga ...

, and

hydrogen fluoride Hydrogen fluoride (fluorane) is an inorganic compound with the chemical formula . This colorless gas or liquid is the principal industrial source of fluorine, often as an aqueous solution called hydrofluoric acid. It is an important feedstock i ...

, are not created by

exhaust gas Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline (petrol), diesel fuel, fuel oil, biodiesel blends, or coal. According to the type of engine, it is discharged into the atmosphere through an ...

. Moreover, smog generated by factories has its own unique mix of contaminants.

Health hazards

Most studies of vog have been in areas where vog is naturally present and not in controlled conditions. Vog contains chemicals that can damage the environment and the health of plants, humans and other animals. Most of the aerosols are acidic and of a size where they can remain in the lungs to damage the lungs and impair function. Headaches, watery eyes, sore throat, breathing difficulties (including inducing

asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...

attacks), flu-like symptoms and general

lethargy Lethargy is a state of tiredness, sleepiness, weariness, fatigue, sluggishness or lack of energy. It can be accompanied by depression, decreased motivation, or apathy. Lethargy can be a normal response to inadequate sleep, overexertion, overwo ...

are commonly reported. These effects are especially pronounced in children and in people with respiratory conditions. Vog generally reduces visibility, creating a hazard for road, air and ocean traffic. The long-term health effects of vog are unknown.

Recent events

Several studies are underway to measure the air quality near volcanoes more carefully. Sulfur dioxide emissions increased on March 12, 2008, when a new vent opened. The increased vog level has caused evacuations and damaged crops. In the summer of 2008 and in 2012, the

County of Hawaii Hawaii County ( haw, Kalana o Hawaiʻi) (officially known as the County of Hawaii) is a county in the U.S. state of Hawaii in the Hawaiian Islands. It is coextensive with the Island of Hawaii, often called the "Big Island" to distinguish it fro ...

received a disaster designation due to the agricultural damage."Vog: Important Information and Facts"
on State of Hawaii Office of the Governor web site A recent multi-year computer-modeling feasibility study, known as VMAP, designed to predict the location and concentrations of vog from Kīlauea was conducted by the University of Hawaii.

References

External links

{{Wiktionary
Hawaiian Vog Photographed from Space Shuttle
* Video of Vog in Hawaii

* National Institute for Occupational Safety and Health Respirator Selection Logic

Hawaii Interagency Vog Information Dashboard
Smog Volcanism Weather events in Hawaii Volcanic degassing