If Earth Never Had Life, Continents Would Be Smaller

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.

Comments

Eh?

[wonkey_monkey]

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.

The point is that life is bad, dummy

[popo]

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?!