Can trees explode from extreme heat or cold or is it an Internet myth that can’t possibly be true?
Internet stories abound that trees have exploded from time to time due to extreme conditions – whether very hot or very cold weather – but can they actually explode from severe temperatures?
While calling it an explosion might be considered accurate in some circles, there is an explanation as to why trees can seemingly explode due to outside factors.
The use of the word explode to describe a tree severely splitting from extreme heat or cold is slightly misleading as trees don’t experience an explosion per se but can be destroyed due to several reasons depending on the severity of temperature and tree species. The destruction and aftermath may mimic an explosion.
Let’s take a closer look at what happens when trees face extreme heat or cold and what species of trees are often affected, and why.
Do trees explode from extreme heat?
When people refer to something exploding, it’s often used in a colloquial sense and not describing an actual explosion. A firefighter’s view of an explosion may be very different from a layman’s.
While you can find many anecdotes of trees exploding during fires, fire professionals generally say they have never come across such incidents personally in their work life.
There have been reports from Australia of eucalyptus trees exploding during bush fires presumably from the very flammable sap inside the tree being heated to a very high temperature. In California and Portugal which is Europe’s biggest grower of eucalyptus, expansive fires have been blamed on the sap in the trees.
The trees don’t explode per se but the sap from a eucalyptus is highly flammable and when heated can catch fire, cause tree bark to fly off and cause new fires up to 100 yards away.
So the results of the sap heating from the fire and the aftermath can resemble an explosion with sap and bark flying off the trees as they burn.
Do trees explode from extreme cold?
One Internet rumor is that some sap-bearing trees such as maples can explode from an accumulation of sap under very high pressure inside trees.
The root pressure inside a maple tree that drives fluids such as sap up the tree is far too low to produce an explosion so this not true and in fact is largely based it seems on several April Fool’s jokes in the early 2000s that were turned into videos that suggested that exploding maple trees were a “thing.” This is not actually the case.
While trees won’t explode from cold per se, frost crack is a phenomenon that can damage trees in very cold conditions.
Frost crack refers to the phenomenon where repeated freezing and warmer temperatures on alternating days in winter can cause large vertical cracks on the outer bark of a tree and on the trunk itself. The combination of repeated cold freezing temperatures followed by thawing causes the cracks to occur.
Trees can survive frost cracks but they can be unsightly and might appear to be from a explosion or eruption of sorts if you didn’t witness it happening.
So again, a tree won’t explode from the sap nor will it explode in the true sense of the word due to extreme cold.
Part of the confusion with trees “exploding” is the colloquial use of the word and perhaps an exaggeration of the impact of extreme heat or cold temperatures.
Having said that, trees and wood in general is very flammable and can be dangerous for a number of reasons that we’ll discuss below.
Wood dust is highly flammable
There have been several high profile sawmill explosions in the United States and Canada that investigators ruled was a result of wood dust that had accumulated and in some cases due to the dust collection system responsible for containing it.
Research
has shown that in order for wood dust to become an explosion hazard, five factors must exist:
- Powder-like wood dust must have accumulated even in a small amount.
- The wood dust must have been dispersed in the air in a sufficient amount in order to be ignited.
- The wood dust must be confined in a closed space such as a room, machine or even a wood dust collection system that collects and contains wood dust in a sawmill.
- Oxygen must be present in the space.
- An ignition such as spark, open flame, or static electricity must be present to ignite the dust and cause the explosion and subsequent fire.
Effectively, wood dust can become an explosion hazard when it exists in the air in a contained space and when a spark or fire source is introduced to ignite the dust which is highly flammable.
Dry wood is highly flammable
The drier the wood the better it burns. This is well known to anyone who has ever built a fire. One of the biggest problems throughout North America facing trees are bark beetles and other pests who kill massive numbers of trees and leave behind very dry, flammable wood in their wake.
When beetles feed on live trees and use trees as nests for their larvae, they slowly kill the trees off by starving their ability to consume water and thus survive. Researchers in both Canada and the US have noted that in many fires, up to 70% – 80% of trees consumed were ones stricken by beetles and other pests. The drier the wood, the easier it burns.
Many of the large wildfires we hear about are due to a variety of factors including dry wood, hot conditions, a wind which helps to spread the fire and of course an ignition source which could be human (campfire, discarded cigarette) or nature (lightning strike) created.
Beetles and other pests who kill trees contribute to the problem by not only destroying the trees in the first place but by turning them into dry kindling which is ideal for stoking a fire that might be started by humans or nature.
Other reasons why wood can cause an explosion
There have been several high profile sawmill explosions in British Columbia, Canada which is the single largest lumber producing province in Canada. In early 2012, two mill explosions resulted in two deaths in each accident along with significant damage to the mills. In both instances, the cause was an accumulation of wood dust in a collection system that was unfit for the size of the mill.
Sawdust is highly flammable and even a spark or high heat can ignite sawdust that is airborne.
Normally, sawmills may use sawdust in winter as fuel for their own furnace system and also to power the kiln that dries their lumber.
In the summer or when they otherwise have excessive wood dust, they may sell excess to others to be used to make wood pellets, animal bedding and for other commercial uses.
But a dust collection system must be used to actually collect the wood dust in the first place. And as mentioned above, sawdust is highly flammable and can easily catch fire if exposed to a spark or other fire source or even very high heat.
Sawmills – especially larger, busy ones – can produce a significant amount of wood dust which not only accumulates on the ground but can also enter the air if the dust collection system is outdated, improperly maintained or too small for the sawmill’s needs.
Sawmills are expensive to build and maintain and given that many have closed over the past few years, remaining ones often struggle to survive. Old machinery is used and maintenance may be spotty.
In this case, the explosion is due to something else but the wood dust being highly flammable can easily catch fire and make the situation much worse.
Summary
Whether trees explode is a largely a matter of how you define the word explode or exactly what entails an explosion. In general terms, trees do not explode in the true sense of the word.
Trees can be severely damaged from extreme heat and extreme cold and a combination of the two. While severe heat can cause sap-filled trees such as eucalyptus or maple trees to “explode” when the sap is heated, it’s the flammable sap and not the wood itself that is the problem.
When severe cold sets in, frost crack can damage trees by causing large vertical cracks on the outside of the trees that may mimic an explosion or severe expansion of the wood, of sorts. But not an explosion per se.
And in case you still wonder if trees can explode, take a look at this video but be sure to watch right to the very end.