2. • 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.
3.
4. • primordial and recycled constituents from the Earth's
mantle,
• assimilated constituents from the Earth's crust,
• groundwater and the Earth's atmosphere.
5. • Magmatic gases and high-temperature volcanic
gases
• Low-temperature volcanic gases and hydrothermal
systems
• Non-explosive volcanic gas
6. • 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).
7. • 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.
8. • The gas release can occur by advection through
fractures, or via diffuse degassing through large areas of
permeable ground as Diffuse Degassing Structures
(DDS).
9. • 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
11. • 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.
12. • The composition and relative volumes of these volatiles
can be measured in a variety of ways:
• DIRECT MEASUREMENTS
• COSPEC MEASUREMENTS
• TOMS MEASUREMENTS
13. • 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, CALIFORNIA
KILAUEA VOLCANO, HAWAII: VOG AND LAZE
14. 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.
15. 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.
16. 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.
17. • INFLUENCE ON THE OZONE EFFECT
• INFLUENCE ON THE GREENHOUSE
EFFECT
• INFLUENCE ON THE HAZE EFFECT
18. • 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.
19.
20. • Enhance global warming by adding CO2 to the
atmosphere (Not more than Human activities. . . )
21. • Volcanic eruptions enhance the haze effect to a greater
extent than the greenhouse effect, and thus they can
lower mean global temperatures.
22. • 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.
23. • 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)
