Dear all
This is one area I am very interested in.
Major volcanic eruptions are capable of causing great change to our weather.
During my tour of the Cascade Mountains NW USA, I went to Mt St Helens which was pluming steam and sulphur clouds about 1 km about the crater. The photos are on my disk. We walked onto Johnstons Ridge and the devastation of May 18 1980 was clearly visible all around us.
The mountain is currently building a new lava dome which is very active. Hence the steam and sulphur plumes I was able to photograph using my new 300 mm ED Nikon Lens. This gives the impression that I am flying over the crater.
The eruptions depicted here are capable of altering the weather as shown by Pinatubo in 1991. (I did not know this thread existed when I placed an article into another thread regarding our unusually cold winter we are having earlier). I have hypothesised that our unusually cold winter for 2007 may be related to a major volcanic blast that occurred at Tungaruhua November 17 2006 in Ecuador. I looked at the sulphur emissions for this volcano which skyrocketed during the eruptions. It could well be related to the sulphur emissions that occurred on this day that has caused a slight but temporary cooling of the southern hemisphere.
There was a massive eruption in 1989 at Lascar in Chile that produced an incredible eruptive column. (Someone wanted to know where it was). I have a photo of it in one of my books. It was not Colima.
Tungaruah (Ecuador) did this on November 17 last year and may be related to our colder than normal winter through the sulphur dioxide emissions. (Any feedback on this would be worthwhile).
Some massive eruptions that have had an incredible effect on global weather includes:-
Laki - In southern Iceland in 1783 that caused hot fogs to occur over Europe. The flood eruption (mainly basaltic lava) caused the death of 1/5 of the population of Iceland and skin peeled off people.
Tambora 1815 - Indonesia. This was a VEI 7 eruption in which 92 kilometres of ejecta was blasted out. This resulted in a major cooling of the northern hemisphere. While it killed 92,000 people, many more were to die from food famines including the potato famine that occurred in Ireland. The temperature of the northern hemisphere fell by 2 to 5 degrees celsius.
El Chichon Mexico 1982. This small volcano roared into life in 1982 and pumped 20,000,000 tonnes of sulphur. Later it was revealed that global temperatures fell by 0.3C on average.
June 1991 Pinatubo. This was a VEI 6 type eruption and the eruptive column towered 135,000 feet during it's climax. It too lowered global temperatures. As a matter of fact at 30 degrees of latitude northwards, the dust cloud was easily visible. I noted it at Armidale in northern NSW at the time.
On tour - June 2007
I visited the site of Yellowstone supervolcano and took numerous photos. In one area, the magma chamber is just 4 km below the surface. It will be the next super eruption that occurs, a VEI 8 eruption.
The magma chamber has a volume of 24,000 cubic kilometres and it is a restless caldera. This is the one to watch. There are numerous monitoring stations there watching it.
Harley Pearman