In order to fully understand the three main

effects of volcanic eruptions on

global climate change it is important to first

look at the two main factors of Volcanic

eruptions.

These are:

a) Volcanic Clouds

b) Volcanic Gases

c) Lava

a) Volcanic Clouds

Clouds are defined in W.I. Rose et al. 2000, Philos Trans Royal Society of London, 358: 1433-1729 as:

“suspensions of particles in the atmosphere”

There are two main types of clouds. These are meteorological clouds and volcanic clouds.

Meteorological clouds consist of particles which are mainly solid or liquid water(H20) which are smaller than 100 microns across. These particles fall throughthe atmosphere in a slower fashion at velocities of lessthan 0.1m/sec.

The difference between meteorological clouds and precipitation is that Precipitation contains large meteorological particles. These particles move at a faster rate than clouds do and also they fall to the earth’s surface more turbulently.

Because of the slow fall speeds of their particles, clouds often persist in the

atmosphere for long periods of time. This can be anywhere from hours to days,

Weeks and, on occasion, months.

Volcanic clouds, on the other hand, are less frequent than meteorological

clouds. These type of clouds occur as a reprocussion of explosive eruptions

(such as from cinder cones, example Mount Tabor; stratovolcanoes, example

Mount St Helens; volcanic domes, example Mount St Helen’s Lava Dome; and

Calderas, example Crater Lake).

Mount St Helens pictured here erupted 8:32 Sunday morning, May 18, 1980.

The explosive eruptions release volcanic gases and hot silicate fragements called pyroclasts. These plumes can reach up to 50km in height.

Like meteorological clouds, volcanic clouds can persist for hours, weeks or longer periods of time.

The diagram opposite is a photograph Taken of El Chicon volcano as it erupts. The volcanic cloud can be seen clearly.

Components of Volcanic Clouds

1) Volcanic Gases2 Pyroclasts3) Aerosol Particles4) Water (H20)

b) Volcanic Gases

Direct sampling and analysis of gases in volcanic clouds has been done only Rarely. Analysis of CO2, on the other hand, has been done more extensively during CO2 flux determination surveys.

Other methods used to collect information about gases has also been used.

The results of this type of study is that volcanic gas in volcanic clouds is mixedand very diluted.

Water vapour occurs at the highest concentration levels. Other gases present In lesser amounts, include the gases of:

1) Carbon Dioxide (CO2)2) Sulfur Dioxide (SO2)

And as trace gases:

1) Hydrogen Sulfide (HF)2) Hydrochloric Acid (HCl)3) Hydrogen (H)4) Carbon Monoxide (CO)5) Hydrofluoric Acid

Although other gases have been found, they are not always found in all eruption samples that have been tested. These

would include volatile metals.

The most important gases emitted are H20, CO2, and SO2.

For more information on volcanic gases, the following website is

recommended:

http://www.gpc.edu/~janderso/physical/volcano.htm

The diagram opposite shows the gas of a volcano being emitted.

c) Lava

The impact of the lava flows emitted from volcanic eruptions is that everything in the path of the volcano is destroyed. All plants, animals and every otherlife-form is obliterated in the blink of an eye. In relation to climate change, theImpact is really rather small. The consequence is that plants are no longer able to produce CO2, one of the major greenhouse gases. This in effectively cancelled out, in most cases, if a large number of animals are destroyed as well. This is because the animals wouldnormally produce oxygen to balance the plants carbon dioxide so there is, overall, no change in the balance of global gases.

The diagram opposite shows a high lava fountain

Of the volcano Pu’u O’o, east of the rift system of

the Kilauea mountain, Hawaii.