Climate catastrophe isn't so certain

[Anomalocaris]

Atmospheric changes have a long-lasting affect. Krakatoa was the last but was actually almost a century past the worst of the volcanic eruption cycle. The worst is believed to have come from Iceland, the worst eruptions seen in several million years. These were not your typical volcanic eruptions you think about, but created mass magma fields which were much more devastating to the climate (it's these that are also believed to have lead to the end of the Cretaceous.

They ended near the beginning of the early 19th century...I had always assumed that the Industrial Revolution with its CO2 emissions had curtailed the affect of the SO2 until it was revealed in new data that there was a rebound effect from volcanic activity of this magnitude. Venus is the best example of this. It just does not end when you cut off the switch...that's why it's called a runaway greenhouse effect.

I think you really need to familarize yourself with some concrete numbers regarding volcanic eruption before sprouting off figures like "worst in several million years". Lakagígar eruption in Iceland in 1783 is a very modest eruption by the standards of what is seen on earth on a time scale of just several hundred years, much less millions of years. It erupted <5 cubic miles of lava and a few tens of millions of tons of SO2. It was soundly beaten in 1812 in both volume of magma involved in eruption and SO2 emission by Tambora eruption in Indonesia. An earlier eruption off the coast of Eastern Australia iaround 1450 is thought to have emitted 3-4 times more SO2 than the Lakagígar.

Lakagígar's claim to record was it may have involved more lava flowing on the ground than other historic eruptions. But many historic eruptions involved more magma that were shot out as tephra instead of flowing out as lava. So hardly does the size of lava flow make Lakagígar particular big in the overall scheme of historic volcanos.

For a large resurgent caldera eruption of the sort that happen once every roughly 100,000 years or so, you will be looking at about 200 times more lava and SO2 than Lakagígar. Last eruption of this magnitude happened about 80,000 years. At least 3 more of them happened just within the borders of the lower 48 states within the last 1.3 million years.

For a truly large eruption like the sort that form large basalt igneous provinces, you will be looking at single eruptions spewing out about 20,000 times more lava and SO2 than Lakagígar. You find this type of eruption about 15 million years ago in Oregon.

The key is even the columbia river basalt province that featured multiple eruptions that may have individually been been up to 20,000 times the size of Lakagígar eruption in 1783 did not seem to cause a global extinction event.

So hardly can we blame a mere sliver of a volcano in Iceland for major climate change with fairly severe extinction implications.

BTW, an asteriod ended the cretaceous. The big basalt province in India, it may have stressed the ecosystem, but there seems to be no evidence that it killed it.

[Polaris]

Atmospheric changes have a long-lasting affect. Krakatoa was the last but was actually almost a century past the worst of the volcanic eruption cycle. The worst is believed to have come from Iceland, the worst eruptions seen in several million years. These were not your typical volcanic eruptions you think about, but created mass magma fields which were much more devastating to the climate (it's these that are also believed to have lead to the end of the Cretaceous.

They ended near the beginning of the early 19th century...I had always assumed that the Industrial Revolution with its CO2 emissions had curtailed the affect of the SO2 until it was revealed in new data that there was a rebound effect from volcanic activity of this magnitude. Venus is the best example of this. It just does not end when you cut off the switch...that's why it's called a runaway greenhouse effect.

I think you really need to familarize yourself with some concrete numbers regarding volcanic eruption before sprouting off figures like "worst in several million years". Lakagígar eruption in Iceland in 1783 is a very modest eruption by the standards of what is seen on earth on a time scale of just several hundred years, much less millions of years. It eruption about 5 cubic miles of lava. It was beaten within 30 years in both volume of magma involved in eruption and SO2 emission by Tambora eruption in Indonesia. An earlier eruption off the coast of Eastern Australia iaround 1450 emitted 3-4 times more SO2 than the Lakagígar.

For a large resurgent caldera eruption of the sort that happen once every roughly 100,000 years or so, you will be looking at about 200 times more lava and SO2 than Lakagígar. Last eruption of this magnitude happened about 80,000 years. At least 3 more of them happened just within the borders of the lower 48 states within the last 1.3 million years.

For a truly large eruption like the sort that form large basalt igneous provinces, you will be looking at single eruptions spewing out about 20,000 times more lava and SO2 than Lakagígar. You find this type of eruption about 15 million years ago in Oregon.

The key is even the columbia river basalt province that featured multiple eruptions that may have individually been been up to 20,000 times the size of Lakagígar eruption in 1783 did not seem to cause a global extinction event.

So hardly can we blame a mere sliver of a volcano in Iceland for major climate change with fairly severe extinction implications.

That's because the volcanic activity that caused the Permian and Cretaceous extinctions covered the size of a continent.

Also you take one incident and you will get relatively negibile atmospheric change, but you have the volcanic activity you mentioned in a relatively short amount of time geologically speaking and there will be much more dramatic (say one to two degree C change) in the atmosphere.

Edit: also the millions of years was that Iceland volcanic system.

[Anomalocaris]

That's because the volcanic activity that caused the Permian and Cretaceous extinctions covered the size of a continent.

Which continent? Neither the Ermensan nor the Siberian flood basalt eruptions near the end of Permean covered an entire continent.

The Deccan flood basalt eruption near the end of the cretaceous is not though to have been responsible for the end of cretaceous, nor did it cover an entire continent. An asteroid laid a layer of iridium right at the termination of cretaceous, and its impact is generally accepted to have caused the K-T extinction event that killed the dinosaurs.

The biggest known flood basalt eruption on earth in the last 500 million years in fact happened in the middle of cretaceous near Java. It was bigger than either Siberian trap or the Deccan trap, and it didn't cause a global extinction event.

The columbia rover flood basalt eruption was not as big as deccan trap, but it was certainly the size of a small continent, and it didn't cause any major extinction event.

So out of 4 big flood basalt events, only one is a strong candidate for having caused a global extinction.

Also you take one incident and you will get relatively negibile atmospheric change, but you have the volcanic activity you mentioned in a relatively short amount of time geologically speaking and there will be much more dramatic (say one to two degree C change) in the atmosphere.

Edit: also the millions of years was that Iceland volcanic system.

What is your evidence Iceland volcanic system is now more active than in millions of years? The icelandic volcanic system has probably been steadily active more or less at the same spot since when North America and Europe first separated about a hundred million years before end of cretaceous. Since end of cretaceous, the hawaiian hot spot probably erupted a good deal more lava than iceland, the total volume of Lava in the entire Hawaiian - Emperor sea mount chain considerably exceeds the volume of Iceland.

The columbia river flood basalt group seems to have emplaced a a amount of Lava comparable to the entire volume of Iceland in just a few enormous eruptions within 1 million years, and Icleand may have taken up to 150 million years to reach present size.

[Polaris]

The common belief is that the end of the Cretaceous was a two-fold event. Volcanic activity sent the climate into disarray (if you go to India and see some of the temples they carved out of basalt, that was created by these eruptions) and the asteroid sealed the deal.

The Siberian flood basalts covered an area in excess of 7 million square kilometers, which is roughly the size of the continent of Australia. Through time and erosion, they now are only 2 million square kilometers.

Vulcanologists surveyed the lava that emanated from Laki and compared it with past eruptions over the lifespan of the volcano.

[orogenicman]

That's untrue. There is no evidence the eruptive frequencies of separate volcanic systems flucturate together. Major volcanic induced climate disturbances are usually caused by extraordinarily high activity in a single volcanic system, such as a single large resurgent caldera or clusters of calderas, or a single hot spot driving a single flood basalt eruption. There simply has been no such truly huge eruptions in the last century or last several tens of thousands of years.

There has only one moderately large eruption in the last 2 thousand years, but at least 4 in the 4 thousand years before that. This suggest even by coincidence, there hasn't been any significant increase in rate of serious eruptions in the last thousand years. Couple this with the fact that the biggest eruption in the last 12000 years is only a fraction of the size of a major resurgent caldera eruption, which happen roughly once every 100,000 years or so somewhere on the globe, which in turn is a tiny fraction of large basalt igneous province eruptions, which happens every few tens of millions of years somewhere on earth.

So it is hard to argue volcanic activity is currently powering any major global climate change.

Atmospheric changes have a long-lasting affect. Krakatoa was the last but was actually almost a century past the worst of the volcanic eruption cycle. The worst is believed to have come from Iceland, the worst eruptions seen in several million years. These were not your typical volcanic eruptions you think about, but created mass magma fields which were much more devastating to the climate (it's these that are also believed to have lead to the end of the Cretaceous.

They ended near the beginning of the early 19th century...I had always assumed that the Industrial Revolution with its CO2 emissions had curtailed the affect of the SO2 until it was revealed in new data that there was a rebound effect from volcanic activity of this magnitude. Venus is the best example of this. It just does not end when you cut off the switch...that's why it's called a runaway greenhouse effect.

Erm, there are no known or demonstrably unambiguous volcanic cycles.