If Earth Never Had Life, Continents Would Be Smaller 64
sciencehabit writes It may seem counterintuitive, but life on Earth, even with all the messy erosion it creates, keeps continents growing. Presenting here this week at the annual meeting of the European Geosciences Union, researchers say it's the erosion itself that makes the difference in continental size. Plant life, for example, can root its way through rock, breaking rocks into sediment. The sediments, like milk-dunked cookies, carry liquid water in their pores, which allows more water to be recycled back into Earth's mantle. If not enough water is present in the mantle about 100 to 200 km deep to keep things flowing, continental production decreases. The authors built a planetary evolution model to show how these processes relate and found that if continental weathering and erosion rates decreased, at first the continents would remain large. But over time, if life never evolved on Earth, not enough water would make its way to the mantle to help produce more continental crust, and whatever continents there were would then shrink. Now, continents cover 40% of the planet. Without life, that coverage would shrink to 30%. In a more extreme case, if life never existed, the continents might only cover 10% of Earth.
Erosion? (Score:2, Insightful)
Then what about all the plants preventing erosion?
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Insightful? What idiots marked this insightful? Plants may prevent erosion short-term, even on an archeological time scale, but on a geologic time scale they accelerate erosion because they break up rocks so efficiently. Make big ones into small ones, and even if the roots hold it in place for 10,000 years that smaller rock is going to start heading for the ocean.
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If a plant broke up the rock below it, then how will that rock get free? The plant's roots broke the rock apart, and the plant's decaying body, (after it dies), will decompose over top of the rock. How, on a 'geologic time scale', would tons of dead plant matter, which then turns to dirt and eventually to rock/coal/etc, which in turn goes even further to geographically lock that small rock where it started, not prevent erosion? The irony forming between your sig and your actual post is delicious. Erosion is
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Go up to the mountains some time, I take it you never have before. Look at any tree tearing a boulder out of the hillside. That tree will die, its pieces will wash down the mountain, and once the roots have decayed the rock will follow. That's why the Adirondacks are little bumps today rather than the towering peaks that they once were. The deep jungle, bogs and swamps are pretty much the only place where your "plant's decaying body, (after it dies), will decompose over top of the rock" scenario would h
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Way to ignore the one relevant question in this entire discussion. Come back when you have a relevant answer. Thank you for the astronomy information by the way. It still doesn't absolve your complete lack of ability to see why your argument is irrelevant but thank you all the same.
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OK, here is the 'relevant answer', condensed. Plants slow erosion in the short (hundreds/thousands of years) term, but accelerate it in the long (millions of years) term.
Eventually the vast majority of organic material that isn't recycled back into the ecosystem will end up in the benthic depths, deposited on the abyssal plains (and apparently processed exceedingly slowly by a recently discovered class of archea). That's why coal deposits (mostly the remains of swamplands that never eroded downs
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Your thought process still puzzles me. Erosion is an amazingly powerful force. It may be slow, but once the Appalachians were taller than the Himalayas, and there used to be a tall range of mountains in the middle of Africa where today there is only veld. Soft matter such as rotting roots erodes much faster than rocks, just ask any farmer. At the time scale of continent building the dinosaurs were around the day before yesterday.
Barren Class M Planets? (Score:4, Interesting)
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Not possible since life created our oxygen rich atmosphere.
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What does that have to do with the parent post? An oxygen-rich atmosphere is hardly necessary for oceans.
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And the point is? (Score:2, Insightful)
.
If the sun were ten times hotter, there wouldn't be life on Earth.
If humans needed to breathe in methane instead of oxygen, there wouldn't be humans on Earth.
See, I can play the game as well....
Re:And the point is? (Score:4, Insightful)
The point is that life is bad, dummy (Score:5, Funny)
Obviously: Since without Life our oceans would be larger, it doesn't take a genius to see that life is negatively impacting the size of our oceans.
As a conservationist I am deeply concerned about this.
Also, by the same token -- it disturbs me that all this out-of-control biology has clearly had an effect on the chemical composition of our atmosphere. Why is no one more freaked out by this? Historic records clearly show that our atmosphere has become tainted with oxygen as a result of all this "life".
Are you okay with chemical changes to the atmosphere, and smaller oceans? Well? Are you?!
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And if life never started on Earth, there would be none of this arguing over the value of systemd.
Now we go full circle, once again.
Re:And the point is? (Score:4, Insightful)
Shutting the mouths of all those "Leave Earth alone!!!" nutcases arguing that it is humanity's duty to reduce it's numbers until it is not a burden to the planet?
That, and being actual... you know... science.
Instead of... you know... a straw man troll in the same vein as "Why is this news for nerds?"
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Hey! Humans! Leave that Earth alone!
Sorry, couldn't resist :)
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All in all you're just a-nother layer of sediment...
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FTFS:
but life on Earth, even with all the messy erosion it creates, keeps continents growing
So, by their model, life, unchecked, will keep continents growing until the continents cover the whole Earth! And their will be no more oceans anymore! That would be a major blow to the surfing and beach vacation industries.
In order to fix this, we should start destroying a bit of life to keep the continents in balance, according to their model.
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Imagine a planet without trolls. Would all civilizations evolve trolls?
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I mean, really now. What's the point of this article?
Who knows, but the point of speculating is to think through different, possible scenarios - the very foundation of prediction, I'd say. Since we don't know all the parameters that are going to shape tomorrow, we have to think through what might happen - what if the car breaks down, what if that cheque is delayed etc - so we can be prepared for things and make contingency plans. In my opinion this is the very thing that makes intelligence an evolutionary advantage: the ability to plan ahead and make reasonab
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I mean, really now. What's the point of this article?
. If the sun were ten times hotter, there wouldn't be life on Earth.
If humans needed to breathe in methane instead of oxygen, there wouldn't be humans on Earth.
See, I can play the game as well....
This is a prime example of an individual who doesn't get the meaning and purpose of science and the pursuit of knowledge.
Eh? (Score:5, Insightful)
It may seem counterintuitive, but life on Earth, even with all the messy erosion it creates, keeps continents growing.
It had never occurred to me to consider that life might cause erosion. That's usually what wind, rain, and gravity are famous for, isn't it? Plant life is pretty famous, surely, for countering erosion by stopping soil getting washed away (a lack of which leading to occasionally disastrous consequences in flash floods, for example).
The sediments, like milk-dunked cookies, carry liquid water in their pores
Milk-dunked cookies don't carry liquid water in their pores. They carry milk. So the sediments are more like water-dunked cookies, moreso because they both taste yucky.
But over time, if life never evolved on Earth, not enough water would make its way to the mantle to help produce more continental crust, and whatever continents there were would then shrink.
Now, continents cover 40% of the planet. Without life, that coverage would shrink to 30%. In a more extreme case, if life never existed, the continents might only cover 10% of Earth.
That's very confusingly written. The first sentence say "if life never evolved on Earth...continents there would then shrink." But then how did those continents get so big in the first place? Surely shrinking continents is only the case when life did evolve, but then theoretically all dies off.
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But then how did those continents get so big in the first place? Surely shrinking continents is only the case when life did evolve, but then theoretically all dies off
Probably the continents would have been bigger in the ancient Earth, because there wouldn't have been so much water yet. Without life, and with increasing amounts of water, the continents would get smaller.
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Well it is far better not to dunk your cookies but to let them crumble between the hammers and anvils of your teeth. That's what most of the adults do, anyway.
Some species of trees, like Douglas fir, are called "primary soil builders" because their roots break up exposed bedrock. John Denver sang a ditty about the flower that shattered the stone. Yes, Virginia, some life forms actively increase erosion.
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It had never occurred to me to consider that life might cause erosion.
No, I think that is something nobody really appreciated in the past; it is only in the last ~10 years that I have started reading an increasing number of articles about this, but it seems that life has been a very major factor in shaping the environment of our planet. There has been a number of great 'events' throughout Earths history - not just "the great oxygenation" if that is the name, but several others, one being (from memory) when
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Awe, cute, you're trying to show us how smart you are ... but you did just the opposite.
Let me help you:
It had never occurred to me to consider that life might cause erosion. That's usually what wind, rain, and gravity are famous for, isn't it? Plant life is pretty famous, surely, for countering erosion by stopping soil getting washed away (a lack of which leading to occasionally disastrous consequences in flash floods, for example).
I went to school in central Florida, widely accepted as a pretty shitty school system in relation to America, which in turn is considered to have a pretty shitty school system in relation to the rest of the civilized world ... yet, you some how managed to attend a school system that didn't bother to teach basic Earth Science in elementary school where everyone learned exactly this. Roots help break rocks
The Search for Life (Score:3)
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Seems like this could have drastic effects on how we search for life. Not only are we looking for planets in the Goldilocks zone, but we now know that if we see too much water it could be a sign that there an absence of life.
I don't think we'd have any clue how much water there "should be" since that depends on the stellar material that created the planet, asteroid impacts and so many other factors we wouldn't know. So practically no, I don't expect this to affect how we search for planets with life and we don't have nearly enough information to consider probabilities. For all we know ocean worlds might be the norm, no life as we know it survives without water so the most obvious place to find life might be in water. Land seems
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Except that global warming would completely swamp this signal.
The easiest way on Earth to get bigger continents is to have an Ice Age. That's been done a few times.
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it has no effect on it, tbh.
this is just about the earth. furthermore, how much water there was to begin with and how the continents were to begin with depends.
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Except unless we saw a before/after picture that were billions of years apart, we'd have no idea what the 'baseline' amount of water was for a planet, and therefore would not have any idea how the amount of water at any point in time might relate to their being life or not.
Piffle (Score:1)
If a planet has liquid water on it it's just a matter of when life exist not if.
Personally I think a lot of cellular level life is out there blowing around like dandelions, they drop in and adapt.
An what about volcanoes and plate tectonic? (Score:2)
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But then you would expect a similar amount of land to disappear again.
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The amount of water subducted into the mantle makes a big difference in what is "brought up from below". Water-containing rock melts at a much lower temperature than unaltered rock, is lighter, is less viscous, and would "float" above the heavier original mantle material. The volcanoes above the subduction zones are much more active because of the rock's water content than they would be otherwise. The less-viscous mantle material means that the smaller plates above it, like India, move around more easily
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I should have replied to yours. I didn't see it until I posted mine. (I used a different control-f search word to avoid duplication.)
We are All Standing on a Big Pile (Score:1)
I guessing there must but a segment of the Geosciences academia are all playing a joke on us to simply prove we are all standing on piles of all of life's shit.
The joke is even better because someone in academia is going to get their Doctorate and full tenure and never have to work a day in their life again.