On a bed of moss on a large rock on a high knoll, below the summit of a steep, forested ridge, lies – prostrate and exposed – a slab of wood.
At first glance, it resembles a fence post, hewn roughly from the trunk of an old Black Cypress-pine. When buried upright, the thick slab would support a strong wire fence. But who would hew a post in such a remote place, and sacrifice their handiwork on a tall, granite boulder?
I pondered some ghostly wood chopper as I rested from my steep climb. Far below, a cow bellowed beside a rusty hayshed. A pair of eagles soared above, hunting for rabbits in the distant paddocks. Along the ridge, gaunt tree trunks tilted erratically; tall, dead cypress-pines, killed by drought.
As I relaxed, chewing into a juicy apple, I spied a shattered ruin of a cypress-pine to my left, its trunk twisted and broken limbs strewn widely. I knelt on the grass surrounded by the decaying shards of this grand old tree. One piece of which, resembling an old fence post, lay on top of a tall, moss-covered boulder.
My whimsical fence post was hewn, not by axe, sinew and sweat, but by 10,000 amperes of electrical current. The tree was killed and the slab was born in a lightning storm.
What about me?
Like many a weary hiker, I grinned triumphantly when I reached the knoll. I had made it, all the way to the top. But that blasted tree replaced my triumph with a hollow humility.
Imagine standing, huddling, cowering, on the ridge on that stormy night; soaked by the rain that extinguished the flames that blackened the shattered cypress-pine. I can conquer the forest on a good day; but it can spit me out, like an apple pip, on a bad one.
Yet, as Adam and Eve discovered, one bite of a juicy apple is all it takes to convert humility to a wild curiosity. So I bit again. What if I had stood on that rock on that stormy night, and the bolt of lightning chose not the old cypress-pine, but me?
Would I have exploded? Would my neck have twisted, my head have spun, and my limbs have been cast aside? If lightning can split firewood from a tall tree, would I have splattered the rocks like jello?
We have all heard stories of rare, luckless souls struck “out of the blue” by a bolt of lightning. Some die, some survive – many with terrible afflictions – and a few recover to be hit again and again according to urban legend.
Dallying in the sun, it dawned on me that I had never heard of a person being blown to bits when hit by lightning. Why not I wondered? Do our jiggly wet bodies absorb the shock? Do we wobble frightfully, exude a puff of smoke and – a millisecond later – lie resting in peace? All in one piece?
The day was too bright for morbid, dark thoughts, so I pulled on my backpack and strode up the ridge, down the gully, and along the dirt track to the car. At home, I vowed, I would ask the font of all knowledge, Google, to tell me everything it knew about lightning, trees and exploding people.
What Google knew
Google of course had much to say on the topic. As always, I learned that my search terms were chosen poorly. The best question isn’t “why do trees explode when humans do not?” but rather “why do trees explode when most things do not?”
Most objects don’t blow up when hit by lightning. Skyscrapers, cars, airplanes and cows all keep their act together. Buildings and vehicles typically remain in one piece unless a gas line or fuel tank is ruptured. Lightning rods protect church spires and office blocks.
Like water, lightning flows along a route of least resistance. When it hits a vehicle or plane, the metal exterior – a mobile Faraday cage – carries the current, leaving the occupants unharmed inside. It is far safer to sit in a car than to lie on the grass in a thunderstorm.
On those rare events when lightning directly strikes some ill-fated individual, much of the current is transmitted around the body, not through it, as the super-charged air creates a narrow band of conductive gas. The remainder of the charge enters the body and surges through the vascular system, where it often causes heart failure.
The dead heart
Unlike a human or a chocolate bar, the center of a healthy tree trunk isn’t soft and gooey. The heart of a healthy tree is dry and lifeless. Heartwood is dead wood.
A tree’s moist living cells are arranged in a narrow band just inside the bark, in the vascular system. This ring of cells contains the xylem – the long, tubular cells that pull water upwards, from the roots to the leaves – and the phloem, which carries carbohydrates (created by photosynthesis in the leaves) down to the roots.
The vascular system is where the watery sap flows. And, as everybody knows, electricity loves to travel through water.
If a tree trunk is wet by rain, the electrical charge may flow outside the trunk, rather than within. The lucky tree may remain undamaged. Commonly, the current surges through the vascular system. On entry, it super-heats the moisture in the cells, creating a boiling pillar of steam. The expanding steam – trapped between heartwood and bark – has nowhere to go, but out. Quickly. Explosively.
This is why trees explode. A tree trunk is an organic pipe bomb, ignited by the mother of all lighters and powered by boiling steam.
Spewing mud and guts
A lightning bolt may shoot down a narrow strip of cells and leave the bulk of the tree unharmed. The exploding cells tear off a thin strip of bark, leaving a surgical scar from the ground to the sky. Other bolts follow a wider course. Not all trees have a hard, dry heart. Old trees decompose, and the core of the trunk forms a dank hollow: “mud guts”, the timber cutters call them.
When lightning strikes a tree with a broken heart, it surges through the rotting core. The expanding column of steam blasts apart the outer trunk, tossing slabs of wood to the ground. Such a fate befell the old cypress-pine that I sat beside. The shattered stem spewed mud, guts and chunks of wood across the moss and rocks. A fast, loud end to a long, quiet life.
Let’s talk about you
Undoubtedly, you will now be comforted to have learned that – should you happen to stand on a stony knoll in a distant forest on a dark, wet night; and should you be smitten by 10,000 amperes of electricity – your body will not be blown to bits. If a search party finds you before the eagles do, your body may be repatriated; bruised, burnt, crinkled and veined. But you will die in one piece.
Unless of course, by a stroke of bad luck, the lightning slams into a mud-hearted pipe bomb beside you. In which case, shards of exploding wood, thicker than fence posts, shall pierce your torso and fling you up – like a lover in a Nick Cave ballad – atop a cold and wet, moss-covered boulder.
Where one sunny day a happy group of hikers – whistling “they call me the wild rose” – will clamber up the rocks, and recoil in shock, as they behold an exposed, prostrate figure beneath a decayed wooden stake; and they shall scream to their friends below, “oh my god, check this out, this is …”
Postscript (don’t worry, be happy)
According to Wikipedia, the world record for being hit by lightning belongs to the late Roy Sullivan, who was struck seven times between 1942 and 1977, while working as a ranger in Shenandoah National Park. And the lightning didn’t kill him. He died years later – at the ripe old age of 71 – after shooting himself in the stomach in a fit of “unrequited love”. Good luck or bad? You tell me. Either way, I hope I’m that passionate – and you are too – should we make it to 71.