Volcanic Gases and Climatic Effects. . .

Dilip Kumar - 12411014

• Variety substances given off by active (or, at times, by dormant) volcanos,

• trapped in cavities in volcanic rocks,• dissolved or dissociated gases in magma and

lava,• directly from lava,• indirectly through ground water heated by

volcanic action.

Sources of Volcanic gases . . . • primordial and recycled constituents from the

Earth's mantle,• assimilated constituents from the Earth's crust,• groundwater and the Earth's atmosphere.

Types of Volcanic Gases. . . • Magmatic gases and high-temperature

volcanic gases• Low-temperature volcanic gases and

hydrothermal systems• Non-explosive volcanic gas

Magmatic gases and high-temperature volcanic gases. . .

• Gases are released from magma through volatile constituents reaching such high concentrations in the base magma that they evaporate.

• Molten rock (either magma or lava) near the atmosphere releases high-temperature volcanic gas (>400 °C).

Low-temperature volcanic gases and hydrothermal systems. . .

• If the magmatic gas traveling upward encounters meteoric water in an aquifer, steam is produced.

• At the surface expression of such hydrothermal systems, low-temperature volcanic gases (<400 °C) are either emanating as steam-gas mixtures or in dissolved form in hot springs.

Non-Explosive Volcanic gas. . .

• The gas release can occur by advection through fractures, or via diffuse degassing through large areas of permeable ground as Diffuse Degassing Structures (DDS).

Composition. . . • All atmospheric gases were derived from inside

the earth and released by volcanic eruptions(except free Oxygen).

• The gaseous portion of magma varies from ~1 to 5% of the total weight. (Water vapor constitutes 70-90%)

• remaining gases include CO2, SO2, and trace amounts of of N, H, CO, S, Ar, Cl, and F.

• toxic compounds:- HCl, HF, H2SO4, H2S

Fumarolic activity

• A variety of sulfur aerosols may be present and sulfur itself may condenses around the fumarole into a crystalline accumulation called sulfaterra (yellow ground).

• On some volcanoes, enough sulfur is present to be mined as an economic resource.

MONITORING GASES. . . • The composition and relative volumes of these

volatiles can be measured in a variety of ways:• DIRECT MEASUREMENTS• COSPEC MEASUREMENTS• TOMS MEASUREMENTS

HAZARDS OF GAS EMISSION. . .• Volcanic gases were directly responsible for

approximately 3% of all volcano-related deaths of humans between 1900 and 1986.

• Volcanic gases are also dangerous because they are hot and toxic.

• Two areas of current volcanic hazard associated with gas emission are:

MAMMOTH MOUNTAIN, CALIFORNIAKILAUEA VOLCANO, HAWAII: VOG AND

LAZE

MAMMOTH MOUNTAIN, CALIFORNIA

Dead and dying trees, south side of Mammoth Mountain Volcano, California in 1998. The trees are dying from high concentrations of CO2 gas in the soil beneath the trees. The most likely source for the gas is from fumarolic activity at depth. Courtesy of K. McGee, USGS.

KILAUEA VOLCANO, HAWAII: VOG AND LAZE. . .

 Vog rising above Pu'uO'o volcano on Kilauea -- This volcanic smog is a mixture of steam and sulfur dioxide gas realeased from Kiauea's active vents since 1983. Courtesey of J.D. Griggs, USGS.

Laze forming at Kilauea, Hawaii -- Pahoehoe lava enters the sea along the southeastern coast of Kilauea on the Big Island of Hawaii. The steam produced from the interaction of hot lava and seawater contains an abundance of toxic HCL gas. This acidic mixture of water vapor and HCL is known as laze. Courtesy of T.N. Mattox, USGS.

Climatic Effects. . . • INFLUENCE ON THE OZONE EFFECT• INFLUENCE ON THE GREENHOUSE EFFECT• INFLUENCE ON THE HAZE EFFECT

INFLUENCE ON THE OZONE EFFECT (indirect role) • HCl gases is confined to the troposphere (below

the stratosphere).• Satellite data after the 1991 eruptions of

Mt.Pinatubo (the Philippines) and Mt. Hudson (Chile) showed a 15-20% ozone loss at high latitudes, and a greater than 50% loss over the Antarctic.

• The particles themselves do not contribute to ozone destruction, but they interact with chlorine- and bromine-bearing compounds from human-made CFCs.

• Fortunately, volcanic particles will settle out of the stratosphere in two or three years.

INFLUENCE ON THE GREENHOUSE EFFECT• Enhance global warming by adding CO2 to the

atmosphere (Not more than Human activities. . . )

INFLUENCE ON THE HAZE EFFECT• Volcanic eruptions enhance the haze effect to a

greater extent than the greenhouse effect, and thus they can lower mean global temperatures.

• Not due to suspended ash particles in the upper atmosphere.

• But due to the amount of sulfur-rich gases.• Sulfur combines with water vapor in the

stratosphere to form dense clouds of tiny sulfuric acid droplets.

• they are capable to decreasing the troposphere temperatures because they absorb solar radiation and scatter it back to space.

EXAMPLES OF GLOBAL COOLING IN THE AFTERMATH OF HISTORIC ERUPTIONS. . .

• LAKI (1783), Iceland (the lowest-ever winter average temperature in 1783-84, about 4.8OC below the 225-year average)

• TAMBORA (1815), Indonesia (year without a summer)

• KRAKATAU (1883), London (the second largest eruption in history)

• PINATUBO (1991), Philippines (the largest sulfur oxide cloud this century)

Thank You. . .

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