Ophiolite
Recalcitrant Procrastinating Ape
Because I have studied dating techniques, geochemistry, vucanology and other relevant disciplines and have confidence, based upon the evidence, that these have a high degree of reliability.But how do you (or they) know that the timescale (the 40,000 years) that they say Mt. St. Helens is; is accurate? They don't know that; because they have no way of testing how "old" magma is.
I am pleased you said "something like carbon 14 dating", since you seemingly understand that C14 dating would be inappropriate in dating volcanic rocks. (Though we could use it for dating any sedimentary layers, with organic matter, that were deposited between lava flows.)They make assumption using something like carbon 14 dating after it's erupted and cooled; but how much does the process of molting rock change the elemental composition of that rock? They can't answer that.
We can answer and have answered the effect of melting upon rocks. The work began seriously over a century ago with research by Bowen at the National Physical Laboratory and has continued, expanded, diversified and grown ever more sophisticated every since. Consequently we know
- The order in which minerals precipitate out of a wide variety of magma types
- The way in which elements are partitioned between the minerals
- The change in the composition of the melt as those minerals crystalise
- The change of chemical stability of each element with changes of melt composition and temperature
- The effect of removal of crystals by sinking, or rising in the melt because of density contrasts
- The extent and nature of post solidification changes upon minerals that are no longer stable
- The extent and nature of zoning in crystals that have grown across a changing range of melt composition and temperature.
If you feel inclined to address these points I'll respond and then move onto the other erroneous views in your post. I hope you will use this as an opportunity to learn, not to pontificate areas you are clearly not well educated in.
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