<p>If the crust were the thickest layer or Earth, several things would happen:</p>

<ol>
<li>It wouldn't be a "crust" any more, by definition. Because this is what a "crust" is: a thin layer on the exterior of something. However, if we assume that the mechanical properties of the crust (being cold and brittle etc) would extend deeper in the Earth, the following applies.</li>
<li>No mantle convection, or at least mantle convection weak enough to probably not affect the surface. Therefore, no volcanoes, no mountain building, no subduction, no recycling of volatile elements, no sub-seafloor hydrothermal vents.</li>
<li>If it's cold enough, the core probably solidified and there is no magnetic field.</li>
</ol>

<p>A good example would be Mars. A planet hypothesised to have tectonic activity in the past, but not any more. The crust of Mars isn't the thickest layer (again - think of definitions), but it is thicker in absolute and relative terms when compared to Earth. I will leave the implications of "Marsifying" Earth on organisms for you to figure out.</p>

CC BY-SA 4.0
2018-07-30T23:32:41.457Z
2018-07-30T23:32:41.457Z
Gimelist
<p>The original question that was put on hold "If the crust were the thickest layer of Earth, what effect would its thickness have on organisms?"  was actually one of those 'counterfactual question' found on my science book, and it was really just a 'reflect upon' question. And it's actually a hard one for me to answer since it's 'what if?'s. So by revising, it would still confuse some poeple, but I guess it's already specific on its own. But I still find it hard.</p>

<p>Follow up question:</p>

<p>And what if it ever was thicker than the mantle or the rest of Earth's layers, can the planet still sustain <em>biological life</em>?</p>

CC BY-SA 4.0
2018-07-30T11:07:08.127Z
I'm glad you want to participate, but this kind of counterfactual question isn't a good fit for this forum; it's difficult enough to understand how the actual Earth works.  If you're willing to be clearer about the definition of "layer", and give the specific thicknesses you're interested in, the folks over at [Worldbuilding SE](https://Worldbuilding.stackexchange.com) might be willing to give it a try.
Spencer
CC BY-SA 4.0
2018-07-30T12:22:27.657Z
Yeah the [Worldbuilding.se] crowd can definitely have a go at this for you, I'd suggest you make it clear in the question whether you mean to divide the other layers of to have the crust be overthickened and the other layers remain as they are but thinner.
Ash
CC BY-SA 4.0
2018-07-30T23:26:28.240Z
Why is this is being closed? This is a perfectly legitimate earth science question.
Gimelist
CC BY-SA 4.0
2018-07-31T13:13:45.313Z
Reworded. Sorry for that :D
beyond stupidity
<geology><crust><geobiology>
Does crustal thickness have anything to do with how life existed and sustained on Earth?
beyond stupidity
# Does crustal thickness have anything to do with how life existed and sustained on Earth?

(Asked by: username_0 on 2018-07-30)

The original question that was put on hold "If the crust were the thickest layer of Earth, what effect would its thickness have on organisms?" was actually one of those 'counterfactual question' found on my science book, and it was really just a 'reflect upon' question. And it's actually a hard one for me to answer since it's 'what if?'s. So by revising, it would still confuse some poeple, but I guess it's already specific on its own. But I still find it hard.

Follow up question:

And what if it ever was thicker than the mantle or the rest of Earth's layers, can the planet still sustain *biological life*?

**Tags:** geology, crust, geobiology

> **Comments:**
> **username_1**: I'm glad you want to participate, but this kind of counterfactual question isn't a good fit for this forum; it's difficult enough to understand how the actual Earth works.  If you're willing to be clearer about the definition of "layer", and give the specific thicknesses you're interested in, the folks over at [Worldbuilding SE](https://Worldbuilding.stackexchange.com) might be willing to give it a try.  
> **username_2**: Yeah the [Worldbuilding.se] crowd can definitely have a go at this for you, I'd suggest you make it clear in the question whether you mean to divide the other layers of to have the crust be overthickened and the other layers remain as they are but thinner.  
> **username_3**: Why is this is being closed? This is a perfectly legitimate earth science question.  
> **username_0**: Reworded. Sorry for that :D  

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## 1 answers

### Answer by username_3 on 2018-07-30. Score: 1 | Accepted answer

If the crust were the thickest layer or Earth, several things would happen:

1. It wouldn't be a "crust" any more, by definition. Because this is what a "crust" is: a thin layer on the exterior of something. However, if we assume that the mechanical properties of the crust (being cold and brittle etc) would extend deeper in the Earth, the following applies.
2. No mantle convection, or at least mantle convection weak enough to probably not affect the surface. Therefore, no volcanoes, no mountain building, no subduction, no recycling of volatile elements, no sub-seafloor hydrothermal vents.
3. If it's cold enough, the core probably solidified and there is no magnetic field.

A good example would be Mars. A planet hypothesised to have tectonic activity in the past, but not any more. The crust of Mars isn't the thickest layer (again - think of definitions), but it is thicker in absolute and relative terms when compared to Earth. I will leave the implications of "Marsifying" Earth on organisms for you to figure out.


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