So, volcanic ash...
Volcanic ash is expanded rock...expanded by heat. It is full of holes, even micro scopic holes.
Volcanic rock, the stuff that flows, molten (melted) down the sides of volcanic mountains, then cools and hardens, is very light to carry, simply because it is porous. Volcanic rock breaks quite easily.
A volcanic erruption may be a 'leak', or it may be an explosion, depending on how hard and solid is the rock above the advancing magma from below.
Mount St. Helens exploded.
We were up there after things had cooled, and in the path of the blast whole mountainsides of trees lay flat, all in one direction, completely bare of needles, branches, and bark. Masses of trees on nearby mountains, in the path of the force, lay like satin, naked in the sun, scoured in seconds by molten tiny particles in a fierce wind blast.
Some rock particles were so small and so driven that they became airborne and were picked up by passing weather and carried countless miles away.
Our home, hundreds of miles away, was dusted by volcanic ash. Wipe our car or our dashboard and we were doing a 'cut' polish.
Orchardists for hundreds of miles were certain they would lose their crops from the coating. Instead, crops were better for years.
Why? Because...
...Molten rocks from a wide area had mixed their minerals, the building blocks of life.
Even then, glassmakers, shoveling up ash from various areas, found that the ash from one area would blow into baubles of a different color than the ash from another area. (Check me on this.)
...Every speck of ash was sharp (glass!), and full of holes (expanded).
What the holes mean is that water gets in and stays there longer...and that the total exposed surface of the piece of rock is larger than if it were a solid.
Volcanic ash holds water, and there is a far greater surface for micro organisms to work on, breaking down the rock, sand, into minerals available for plant nutrients.
The sharpness of each tiny piece means that it would penetrate hard soil, for one thing, and even the surfaces of existing rock, in every tiny crevice.
Add rainwater, and the soil micro organisms go right to work.
There have been volcanos so huge that the clouds of volcanic ash were so big that they blotted out the sun...some around the world, for a year. There was one such volcano in the 1800's, I heard. Crops failed...and people died.
Then, when soil micro organisms carry the mineral nutrients to plant roots...
...Plants are very selective in which minerals they take up...and how much of each they take up!
Food plants are the smartest of all...they balance their mineral content (and the things they make out of minerals and water and sunlight and shade), exactly right for some living creature's well-being. Because, if a living creature loves the plant and its contents, the creature will make darn sure to scatter the plant's seeds to get more of that kind of plant.
It's automatic, things that eat certain plants act as 'legs' for rooted organisms, to perpetuate the species.
If, however, plants can't find all the right minerals they need, in the amounts they need (or the micro organisms to fetch them), plants will manufacture other things out of what they DO find.
When this happens, the plant is stressed...vulnerable and open to anything that will break it down into soil once more. Plagues start this way...just as we may be plagued by the forces that break us down into soil, once more.
Minerals, balanced for us by plants, build us strong and beautiful, immune to most plagues...maybe even all.
There it is, folks. The little word we all depend on...'immunity'.
We break the chain of life at our own peril.
I say we haven't broken it enough, yet...because we still exist in this era of conditions suitable for human life...but we have certainly strained the plants that support us...likely by straining and eradicating the micro organisms that support plants.
F.