What would change if our Earth lacked mountains? (Geology)

Question

I just asked myself what is the role of the mountains on Earth? Well there's a well known role for the climate and weather.

But is there a kind of physical or geological role? What would happen if our Earth had no mountains on it? Would we have more earthquakes? I suppose erosion will be much heavier than it is now.

I would like to get some kind of scientific answer if possible from a geological point of view!

EDIT: I posted the Question later also in earth science SE after reading the comment of user6760

Answer 1

No Plate Tectonics

To have a world with no mountains occur naturally, there must be no plate tectonics. To have no plate tectonics, there must either be no moon, or the moon must be tidally locked to prevent its gravitic influence causing heat-producing deformation of the world.

A consequence of this is that there would be no earthquakes and erosion would eventually level land and sea-floor alike until it was eventually all an equal depth beneath the water (aside from small solar tides). There would be no geomagnetic field (that being caused by the same processes as plate tectonics), which would allow higher radiation levels at the surface.

The Mountains were taken away!

If earth's mountains were magically instantly removed, there would be immediate repercussions. All that stone has mass, and the crust beneath which had been pressed into the mantle would rebound, causing worldwide earthquakes. Volcanoes would erupt as their plugs of stone were removed or weakened.

All this is not considering the effects on the global weather patterns.

In the long term, mountains would reappear as plate tectonics continued to deform the landscape.

Answer 2

In addition to the answer by Monty, I think it's important to mention that mountain formation has a side-effect of "excavating" minerals from deep down within the earth and bringing them to the surface. When plates collide to form mountains, the bottom layers of Earth's crust rise to the top with the mountains. This allows us to then find various metals and minerals within the mountain ranges. Plate tectonics is effectively a blender for the Earth's crust.

Without mountains, mining would have been very different. We would have to dig down several miles before finding any minerals/metals, and to make things worse we'd have no tools for such a job since we've been manufacturing them out of... metals. Any materials we would have available to us on the surface would be too soft to dig the harder materials down below.

Answer 3

If you want to see what happens without tectonic mountains, you might do well to look at Australia, much of which has been geologically stable for a very long time. Outcomes of that include the majority of the country being very flat and quite samey ( you can drive hundreds of miles without more than the mildest inclines ) and in places like the Blue Mountains the mountain range is actually created as the result of a canyon system from an ancient river. If you wanted to avoid this type of terrain you would either need to have no eroding agents ( which makes a challenging environment to design ) or to have very hard rocks that don't erode, which is a challenging environment to populate as that is where most soil comes from.

One good bet for this type of environment might be a very old planet, tectonically dead and then eroded down about as far as it can be. Of course, the natural consequence of this on an earth-like planet would be that it would be covered by a fairly uniform depth of water, so I guess any life you have there would probably be aquatic. That said there are some arguments that tectonics were a necessity for life as we know it, so evolution without that factor might travel along a very different path.

Answer 4

Weathering of rocks is how CO₂ is removed over time. So without erosion the carbon cycle fails and the Earth ends up like Venus.

Answer 5

Two things that are really important:

1. erosion of mountains soaks up a lot of Carbon from the atmosphere, so much so that even the plants would choke on excess CO2 if they didn't.

2. mineral cycles, without continuous turnover certain elements, Phosphorus for one, get washed to the sea and that's where they stay, no mountains would mean that life as we know it would go under for lack of Phosphorus, Sulfur and possibly even Iron.

As a note erosion of mountain-less terrain is relatively slow due to the lack of Orographic Rainfall.