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#1 |
Critical Thinker
Join Date: Mar 2004
Posts: 377
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How can plants grow through asphalt?
Last autumn I had my front yard paved with asphalt. Prior to this I sprayed the area with diesel to kill plant seeds, as I was adviced to do.
However, now I have two lange bulges in the paving, and I'm pretty sure that a dandelion will soon emerge from each of these spots. The question is how on earth this is possible? It of course means that the diesel did not kill the seeds, but how can a flower actually break through the asphalt paving? How does it know in which direction to grow? After all, there's not much light passing through the paving? And where does the force to break the paving come from? I realize that this is a slow process, but nevertheless it requires considerable force to actually break the paving. Anyone have any answers to this? And what can I do about it now? -Øyvind |
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#2 |
Guest
Join Date: Apr 2004
Posts: 8,504
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Re: How can plants grow through asphalt?
Quote:
IOW, how is that NOT probable? I'm not even going to ask why you paved your yard. I'm sure you had good reason. I've even contemplated to so meself. |
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#3 |
Terrestrial Intelligence
Join Date: Aug 2001
Location: Terra Firma
Posts: 6,451
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Sometimes nature can play magic tricks on you. A plant grows through asphalt and you think it must have broken through. You are probably thinking about it the wrong way around.
I think it is more likely that the asphalt breaks first, and this causes an opening in which a seed can fall. If the ground under the asphalt gives it enough nutrients, it will sprout and the plant will go through the crack, making it appear as if it broke through. Accidental Magic! There isn't much light passing through the paving, but then again there's not a lot of light passing through the soil either. And still seeds manage to grow in the right direction, even if they are a few decimeters underground. How they do it? Gravity. |
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Perhaps nothing is entirely true; and not even that! Multatuli |
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#4 |
Graduate Poster
Join Date: Aug 2003
Posts: 1,299
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Get yourself a propane torch and a stamping tool (piece of 2x4 or a log will do).
Heat the bulge up until the asphalt is soft. Stamp it down flat. Wonders of nature crushed by humanity's need to pave. |
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#5 |
Merchant of Doom
Join Date: Sep 2002
Location: Not in Hell, but I can see it from here on a clear day...
Posts: 14,883
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Pave the whales!!!
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History does not always repeat itself. Sometimes it just yells "Can't you remember anything I told you?" and lets fly with a club. - John w. Campbell |
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#6 |
Critical Thinker
Join Date: Mar 2004
Posts: 377
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Re: Re: How can plants grow through asphalt?
Quote:
Yes, dandelions are common here, but the point was *how* they are able to break up the asphalt. |
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#7 |
Terrestrial Intelligence
Join Date: Aug 2001
Location: Terra Firma
Posts: 6,451
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They don't break the asphalt. You probably live in geologically active area where the ground moves and breaks the asphalt because that doesn't move with the ground. Then when the asphalt is broken, there is place for the dandelions to grow.
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Perhaps nothing is entirely true; and not even that! Multatuli |
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#8 |
Critical Thinker
Join Date: Mar 2004
Posts: 377
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Quote:
Here's an image of one of the spots, from two different angles: ![]() That doesn't rule out your theory of the seed falling into a crack, but it shows that the sprout quite violently breaks the asphalt. |
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#9 |
Critical Thinker
Join Date: Mar 2004
Posts: 377
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Quote:
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#10 |
Critical Thinker
Join Date: Mar 2004
Posts: 377
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Quote:
Good one, Huntsman! ![]() |
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#11 |
Merchant of Doom
Join Date: Sep 2002
Location: Not in Hell, but I can see it from here on a clear day...
Posts: 14,883
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mroek,
Actually, the spots you see as "breaking through" are more likely the effects of thermal stress. With asphalt this can happen within a few years of it being laid...asphalt is not exactly the best paving material (but it is cheap). However, what happens is the asphalt expands in the summer or when the heat is higher, and contracts when it gets cooler. When it contracts, it creates minute cracks through the surface. On close inspection, one can generally see these hairline cracks running throughout any asphalt that's been there for a few years or longer. Anyway, once these weak spots are there, the next step is expansion. Summer comes along, temperatures rise, and the asphalt begins to expand. The expansion causes it to deform. Since it can't deform downwards (the Earth is in the way) it bulges up, producing bulges much like the ones in your picture. You'll also see long rows or raised asphalt that are qualitatively identical. From here, it follows along with what Earthborn is saying. Once any sort of hole develops that gan give a seed access to the ground underneath (or enough nutrients from dirt collected in the crack), a plant will begin to grow. Once the plant starts growing, it can very well speed up deformation in the asphalt. However, this is because the plants will find and us any minute cracks that develop, rather than the plants being able to break through the material. |
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History does not always repeat itself. Sometimes it just yells "Can't you remember anything I told you?" and lets fly with a club. - John w. Campbell |
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#12 |
Did you spill my pint?
Join Date: Dec 2002
Location: Scotland
Posts: 2,052
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I've seen this often with various plants. Here's an explanation from the New Scientist. It refers to mushrooms.
Quote:
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Knees bent, arms stretched, Ra! Ra! Ra! |
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#13 |
Critical Thinker
Join Date: Apr 2004
Posts: 448
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Darn it, mummymonkey! I actually had the answer to this question, and you beat me to it! I was taught this in high school (a veeerrry! long time ago) as part of an advanced sciences course. We were discussing the power of hydraulics at the time, and the question was posed by the instructor.
Here's another good question I remember. How does water get to the leaves at the top of a redwood tree? The column of water from the root to the leaf represents a substantial amount of weight. I can't remember exactly how much, but I'll run the math and post it if I get the time. |
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#14 |
Graduate Poster
Join Date: Feb 2004
Posts: 1,855
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It's a combination of osmosis (driven by evaporation and the production of sugars in the photosynthetic leaves) and capillary action.
Dangle the end of a paper towel strip in water, and water will soak upwards, against the flow of gravity. The attractive force between the water molecules and the gaps in the towel are (on a small scale) much more powerful than the pull of the Earth's mass. |
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#15 |
Graduate Poster
Join Date: Sep 2002
Posts: 1,527
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Dandelions have a long taproot and will overwinter. About the only thig diesel sprayed on the surface will do is pollute the groundwater. To kill dandelion, you need to use an herbicide that contains salt of dicamba.
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#16 |
Critical Thinker
Join Date: Apr 2004
Posts: 448
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Quote:
The current theory is called the cohesion theory because it depends on the cohesion of water molecules to each other through hydrogen bonding between the molecules. In a very small diameter tube, the string of water molecules has a tensile strength equal to steel wire. As the leaves transpire water out of their surfaces, they pull the "water wire" up the tubes (called xylem). These tubes are roughly 40 um in diameter. As far as I know, it does not have anything to do with osmosis, or the attractive force between water and the xylem elements (capillary action). But hey, I've been wrong before. |
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#17 |
a flimsy character...perfidious and despised
Join Date: Nov 2002
Location: Out back preparing the bunker for the next Civil War
Posts: 49,380
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I don't see anything green coming up through those bulges. More likely just volcanic activity. I would move as soon as possible.
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Counting the days to Civil War II. |
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#18 |
Philosopher
Join Date: Aug 2003
Posts: 6,215
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mroek---The photo looks very much like the bride of Hulk, laying on her back. A possible new movie release to join the brides of Frankenstein and Chuckie
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I lost my mind many years ago and it hasn't affected me a bit...a bit..a bit..a bit. |
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#19 |
Man in Black
Join Date: Jul 2001
Posts: 3,664
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Did you use a good asphalt sealant when the work was done? Judging by the photos the asphalt wasn't sealed.
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#20 |
Critical Thinker
Join Date: Mar 2004
Posts: 377
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Quote:
I've never heard of asphalt sealing, but I'd guess it's some chemical sprayed onto the asphalt to seal the pores? |
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#21 |
Critical Thinker
Join Date: Mar 2004
Posts: 377
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Quote:
There are no volcanos in Norway, so maybe I'm about to get my 15 minutes soon...? ![]() |
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