Why do pine trees make a thumping noise?
March 9, 2012 6:23 PM
Help me figure out why I hear and feel a thumping noise when I sit next to pine trees.
A little background: I was in San José, Costa Rica, last summer and ended up reading in a park that had a few pine trees scattered around (I don't know the species, however). I sat on the ground with my back resting against a pine trunk.
It wasn't long before I started hearing a bizarre thumping noise. From what I could feel from the ground, it should have been somebody jumping/stomping or people hurling bowling balls onto the soil from the nearby house's roof. I looked around--nobody. I looked (okay, creeped) at the adjacent house and nothing was going on. I looked up the tree and no critters were scampering around or woodpeckers going to town. This continued to happen, so I just accepted it as part of the experience abroad and thought nothing of it.
Fast forward to this month. I go to school at a college in southern Arkansas, and nearby there's a very primitive park (read: cleared footpaths) on a bluff overlooking a river. Along the bluff's edge are pine trees exclusively, with deciduous trees on the bluff's side. Last Friday, I was doing some reading and rested my back against a pine's trunk and--you guessed it--the same dull, thumping noise happened again.
The sound and sensation is similar to somebody whacking a carpeted floor with their hand: a very muffled bump that you can feel if you're sitting on the floor. But, like in Costa Rica, nobody (and nothing) was to be found. I felt the thumping noise in the ground and in the trunk, so I was wondering if the pine tree itself was responsible for this noise--sap moving around?--or if a parasite was tunneling around inside or below.
Anyone have any clue what's going on here? I'm sure there's a scientific explanation for it, but it's things like this that would have made the ancients believe in tree spirits & such. I'm not losing sleep over this mystery pine thumping, but it sure is weird.
A little background: I was in San José, Costa Rica, last summer and ended up reading in a park that had a few pine trees scattered around (I don't know the species, however). I sat on the ground with my back resting against a pine trunk.
It wasn't long before I started hearing a bizarre thumping noise. From what I could feel from the ground, it should have been somebody jumping/stomping or people hurling bowling balls onto the soil from the nearby house's roof. I looked around--nobody. I looked (okay, creeped) at the adjacent house and nothing was going on. I looked up the tree and no critters were scampering around or woodpeckers going to town. This continued to happen, so I just accepted it as part of the experience abroad and thought nothing of it.
Fast forward to this month. I go to school at a college in southern Arkansas, and nearby there's a very primitive park (read: cleared footpaths) on a bluff overlooking a river. Along the bluff's edge are pine trees exclusively, with deciduous trees on the bluff's side. Last Friday, I was doing some reading and rested my back against a pine's trunk and--you guessed it--the same dull, thumping noise happened again.
The sound and sensation is similar to somebody whacking a carpeted floor with their hand: a very muffled bump that you can feel if you're sitting on the floor. But, like in Costa Rica, nobody (and nothing) was to be found. I felt the thumping noise in the ground and in the trunk, so I was wondering if the pine tree itself was responsible for this noise--sap moving around?--or if a parasite was tunneling around inside or below.
Anyone have any clue what's going on here? I'm sure there's a scientific explanation for it, but it's things like this that would have made the ancients believe in tree spirits & such. I'm not losing sleep over this mystery pine thumping, but it sure is weird.
I have experienced hearing insects that have infested a tree eating under/in the bark, but I can't imagine that it could be perceived as a "thumping" sound. Somehow I doubt that it is not related to the tree, or to insects.
posted by HuronBob at 7:05 PM on March 9, 2012
posted by HuronBob at 7:05 PM on March 9, 2012
A rodent, underground.
posted by the Real Dan at 7:18 PM on March 9, 2012
posted by the Real Dan at 7:18 PM on March 9, 2012
Some squirrels cut pine cones from branches, in order to pick them up on the ground and eat them or store them for later. That could be it -- pine cones hitting the ground from a multi-story drop.
posted by Cool Papa Bell at 7:44 PM on March 9, 2012
posted by Cool Papa Bell at 7:44 PM on March 9, 2012
Rube R. Nekker, via Cortes, addressed the question I had for you-- wind conditions:
Trees? There is a large pine tree at my house that thumps under the right wind conditions ...
posted by Rube R. Nekker
Pine trees are stabilized by a stiff taproot and by a mass of lateral roots that act like guy wires.
The lateral roots are really tangled looking and full of elbows.
This is very tentative, but I think the thump occurs when wind pulls the lateral roots tight and irregularity in one root, such as an elbow, 'plucks' another root under tension like a finger plucking a big underground wooden guitar string.
posted by jamjam at 8:13 PM on March 9, 2012
Trees? There is a large pine tree at my house that thumps under the right wind conditions ...
posted by Rube R. Nekker
Pine trees are stabilized by a stiff taproot and by a mass of lateral roots that act like guy wires.
The lateral roots are really tangled looking and full of elbows.
This is very tentative, but I think the thump occurs when wind pulls the lateral roots tight and irregularity in one root, such as an elbow, 'plucks' another root under tension like a finger plucking a big underground wooden guitar string.
posted by jamjam at 8:13 PM on March 9, 2012
jamjam: I forgot to mention that it was incredibly windy on the afternoon I went up to the Arkansas bluff. Your explanation makes sense of what I was experiencing: thumping in the ground (the lateral roots) and the tree trunk (link with the taproot).
I don't remember the specific weather conditions for the day I was in the Costa Rican park, but it stormed almost every day I was there, so I'm sure it was at least a little windy.
posted by huxham at 9:06 PM on March 9, 2012
I don't remember the specific weather conditions for the day I was in the Costa Rican park, but it stormed almost every day I was there, so I'm sure it was at least a little windy.
posted by huxham at 9:06 PM on March 9, 2012
whoa whoa whoa peoples ... it thumps against a roof, not a tree freestanding in the clearing!
ask me i am likely to tell you infrasound makes your eyeballs warble or the ents are saying hallo ...
but i like jamjams answer!
posted by Rube R. Nekker at 1:52 PM on March 10, 2012
ask me i am likely to tell you infrasound makes your eyeballs warble or the ents are saying hallo ...
but i like jamjams answer!
posted by Rube R. Nekker at 1:52 PM on March 10, 2012
This thread is closed to new comments.
posted by Sassyfras at 6:41 PM on March 9, 2012