View Full Version : The Environment

11th Apr 2002, 05:15
I read once that Mt. Saint Helen's little burp put as much CO2 into the atmosphere as the human race has done so far. In total. Since the caveman discovered fire.

If this isn't the case, somebody please correct me.

If it is the case, aren't we being arrogant ants to assume we can control / maintain the climate around this volatile ball of magma we call Earth?

Gunner B12
11th Apr 2002, 05:21

I don't see where all that C02 could have come from after all there isn't a lot of gas below the surface of the earth. What was thrown out was surely ash and that getting into the atmosphere would probably have had a cooling effect by blocking out sunlight.

:confused: :confused: :confused:

11th Apr 2002, 07:48
Nah, volcanoes spew out large amounts of gas as well as lava and stuff - that's why pumice is all frothed up: from the gas bubbles. Heat any rock up and you'll release all sorts of gases - water vapour, carbon dioxide, sulphur dioxide.

And LnS, isn't the real arrogance to suppose that we can just continue to spew out filth into the atmosphere and that somehow nature will take care of it and it'll all be alright ?

11th Apr 2002, 07:59
Programme on BBC 2 the other night about gases released by volcanic action.
Basic chemistry about gases dissolved in volcanic material under great pressure are released with what can be catastrophic consequences. You can see the effect of gas dissolved in liquid by observing a pop bottle being opened and seeing the gas bubbles that form when the pressure is released.
I do not know about the amount of CO2 released by Mount St.Helens but sounds not far off the mark to me.

Gunner B12
11th Apr 2002, 08:25
Ok so I showed my ignorance. So I corrected my lack of knowledge and present from a number of web sites (along with an interesting link) the following.

Hope it answers the questions.

The most common elements in materials erupted by volcanoes are: silicon (Si), oxygen (O), magnesium (Mg), iron (Fe), aluminum (Al), calcium (Ca), sodium (Na), potassium (K), titanium (Ti), phosphorous (P), carbon (C), hydrogen (H), and sulfur (S). Alone and in various combinations and proportions they make an amazing variety of materials including basalt, diamonds, and water.
The major gases in magma are water vapor (H2O), sulfur dioxide (SO2), and carbon dioxide (CO2). They usually make up only a tiny percentage of the magma by weight (often around 1% or less). However, because gases have such a huge potential to expand, even these tiny percentages have very large effects on the explosivity of an eruption.


How much CO2 was released?

I don't have an exact number. At Mount St Helens the maximum measured emission rate was 2.2X10^7 kg per day. The total amount of gas released during non-eruptive periods from the beginning of July to the end of October was 9.1X10^8 kg . I do not have an estimate for the volume of CO2 released during the Plinian eruptions. As a long-term average, volcanism produces about 5X10^11 kg of CO2 per year; that production, along with oceanic and terrestrial biomass cycling maintained a carbon dioxide reservoir in the atmosphere of about 2.2X10^15 kg. Current fossil fuel and land use practices now introduce about a (net) 17.6X10^12 kg of CO2 into the atmosphere and has resulted in a progressively increasing atmospheric reservoir of 2.69X10^15 kg of CO2. Hence, volcanism produces about 3% of the total CO2 with the other 97% coming from man-made sources. For more detail, see Morse and Mackenzie, 1990, Geochemistry of Sedimentary Carbonates.

Am I forgiven for my previous ignorance?

Edited coz the last question somehow ended up in the middle of the post.

11th Apr 2002, 08:45
Exactly. And that's the problem.

Volcanic activity is part of a cycle: sure, CO2 is released but at the same time atmospheric CO2 is buffered into carbonate rocks.

These carbonate-bearing rocks are drawn back under the Earth's surface at subduction zones and reprocessed. So the total amount erupted is balanced by the amount re-absorbed.

Similarly, animals breathe out CO2 but then this gets turned into trees which die and get fossilised as peat and coal so the CO2 again gets locked up under the Earth's surface. And the dead animals turn into oil.

What we're doing is digging up millions of years worth of locked-up carbon and burning it back into the atmosphere over the last 100 years and the next 200 years or so before it's all used up.

650 Million years into 300 years just doesn't go :(