Alan Stahler: The make up of wildfires
August 8, 2018
Every atom has, at its core, like a pit in a peach, a nucleus. Surrounding the nucleus is a cloud of electrons. We're all familiar with electrons — pet a cat on a dry winter's day, and electrons jump between your hand and the cat.
There are nearly a hundred different types of atoms in the world, and they all have different personalities — mercury atoms like to screw with our proteins, which makes mercury toxic. Helium atoms like to float, useful in balloons.
The personalities of oxygen atoms include a couple of deadly sins: More than any atom but one, oxygen atoms are greedy for more than their share of electrons. They'll snare electrons from iron, for instance, causing it to rust.
When life first evolved on Earth — when the right combinations of atoms got glued together to create a living system — that life had the luxury of floating around in its own dinner bowl — basking in a bowl of nutritious soup, rich in molecules these early life forms could eat — clumps of atoms from which life could snag the sub-atomic particles that you and I snag from our food, the sub-atomic particles we need to keep ourselves going. Food is rich in electrons.
Swimming around in the soup bowl worked fine for millions of years. But some times, some places, the soup ran thin.
A group of bacteria discovered a way to harness the energy of the sun, to pluck electrons off the sulfur atoms, in hydrogen sulfide, H2S — the smelly gas that spews out of volcanoes — they evolved a way to steal these electrons from the sulfur in hydrogen sulfide, and use those electrons to make electron-rich food. This broke up the H2S molecule, leaving pure sulfur, which was useless to them, so they just threw it away.
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This worked fine, so long as the bacteria were near a volcano. But then, a group of these bacteria figured out how to get electrons from molecules much easier to find … they evolved a way to get electrons from H2O — water. This was phenomenal; these bugs had figured out a way to steal electrons from oxygen.
Stealing electrons from oxygen broke up the water molecule. Pure oxygen, at the time, was useless to these bacteria, so they just threw it away. And so, oxygen began to build up, first in the water, then, when the water became saturated, the oxygen bubbled up, into the atmosphere.
And so, for the first time — two or three billion years ago — there was oxygen in the oceans, oxygen in the air. Roughly half a billion years ago, oxygen had built up enough to enable the evolution of new beasts: Fish, frogs, dinosaurs, mammals, people.
And oxygen in the air made possible another beast that the world had never before seen. Roughly half-a-billion years ago, the world saw the ignition of the first wildfire.
This morning, a few hours before dawn, I watched the crescent moon rising … the red crescent moon. Last Friday morning, several hours before dawn, ash fell from the sky. It looked like nothing, so much as falling snow.
There was something about the ash that made me wonder where it was coming from —not which fire, but was it from a tree, a remnant of someone's house, someone's furniture or someone's clothing?
This story has been about chemical elements: Helium and sulfur and oxygen. But through all of this threads the human element. We hear stories of breakneck driving, people running for their lives, losing everything they own, losing people they love.
The rains will come again, and so will the fire. And so will the questions: How can we as individuals, how can we as a society, be better prepared for the fire next time?
Al Stahler enjoys sharing his love of nature with students of all ages. His science stories can be heard on KVMR-FM (89.5 MHz), and he may be reached at firstname.lastname@example.org