I was thinking of making a world that is filled to the brim with mountains. I'm not saying that the world is just mountains, but the area or terrain is so difficult that it's hard for land vehicles to explore. I don't what else to say since this idea is new to me and I'm having a hard time molding it.
Countries with land areas mainly consisting of mountains like Nepal, Greece, and some other European countries have relatively small and stable and even declining populations. So I get that if the vast majority of the Earth's land surface was made of mountains the global population would be much smaller due to limits in agriculture. It is much harder to make crops grow in an irregular terrain than it is on the plains. Transportation would be also harder because it is harder to build roads and rails in mountains.
I'd start by thinking about how those mountains would form. As far as I know, plate tectonics (in the long term) and volcanic activity (in the not-quite-that-long term) are mainly responsible for mountains to build up.
To get more mountains than we have on earth, I'd say your planets crust would need to be rather thin (compared to earth), so that tectonic pressure would more readily fold the plates instead of pushing one plate on top of the other. A thinner crust would also increase volcanic activity, further increasing the chance of mountains building up. Add enough water and you've got continents of mountainous islands and island chains (where tectonic plates are pushed together) paired with oceans full of underwater volcanoes (where tectonic plates move away from each other). I'd assume that you'll get a whole lot of tsunamis on that planet.
(I'm the wrong person to answer anything about hard science on this topic, though.)
Lots of thoughts in no particular order
If you're thinking of a super Earth, your mountains will be relatively small. A bigger planet will have more gravity that will cause taller peaks to be unstable and collapse (landslides). Smaller planets have relatively larger mountains. For example, Olympus Mons on Mars is 15 miles tall and the Mountain ring on Iapetus is as tall as 10 or 12 miles. By comparison, Mauna Loa on Earth is only 6 miles tall. If you look at the list of tallest mountains in the solar system, the bigger ones tend to be on the smallest planets. Of course erosion also plays a part. Other bodies with bigger mountains tend to not have an atmosphere to cause erosion.
I don't have a link or a good source to cite, but it seems to me that most mountain forming processes would be enhanced by a thinner crust and/or increased volcanic activity. Maybe you can have a young planet that hasn't cooled enough to have a thick crust. Then put it through a period of heavy meteoric bombardment that shattered the crust. This would result in higher amounts of vulcanism so you get "extra" mountains and lots of impassable terrain from normal subduction/delamination, impact craters and volcanos. I'm not sure what that does to the atmosphere though. Is it a cool climate because of nuclear winter? Is it a hot humid climate because of vulcanism? How do the seas fair with all the extra volcanic activity? I don't think you'd get run away global warming since these aren't greenhouse gas clouds? Need someone smarter than me to answer those questions.
imtaar has a good point about the balancing of the planet. Earth has a wobble and it was made worse by all the dams built in the northern hemisphere. Crazy to think that humans managed to affect the rotation of a planet! But depending the methods you use to get your mountains, you may have to account for some crazy axial procession. Imagine what our planet would be like if the poles of the planet drifted by several feet or even miles per year. GPS would need monthly or daily updates to account for the ground not being where it was yesterday. Astronomical charts from just a few decades ago would be nearly useless. Tropical years could be days shorter than the astronomical year which would mess with planting days.
How would it affect the geography, environment, and gravity of the planet?
Geography: There would be loads of mountains. Mountains are part of geography. Source.
Environment: See above. More mountains.
Gravity: Depends only on the total size of the planet. Mountains don't make much of a difference. Source.
When the tyre of a car is balanced, certain weights are attached at certain places on the rim so that there are no vibrations when the tire is spinning at high speed.
Over millions of years, the mountains and other geography is set in such a way that earth rotates in a balanced way. If you suddenly place large mountains randomly, this could unbalance the rotation of earth.
In your world, you cannot place mountains in an artificial way. Let them be formed through natural processes.
- Mountain roots act like pegs embedded in the ground and they work as stabilizers for the earth.
- Mountains take part in isostasy, a concept of the gravitational equilibrium that explains the balance of topographical undulations on the Earth’s surface.
- Mountains help our climate stay relatively stable in between catastrophes.
As told here:
The book "Earth" by Professor Emeritus Frank Press , is a basic reference book in many universities . The book says that mountains have underlying roots. These roots are deeply embedded in the ground, thus, mountains have a shape like a "peg".
Dr. Press explains that Mountains play an important role in stabilizing the crust of the earth. They interfere with the shaking of the earth. The modern theory of plate tectonics also states that mountains work as stabilizers for the earth.
As told here:
Isostasy, ideal theoretical balance of all large portions of Earth’s lithosphere as though they were floating on the denser underlying layer, the asthenosphere, a section of the upper mantle composed of weak, plastic rock that is about 110 km (70 miles) below the surface.
This means that an excess of mass seen as material above sea level, as in a mountain system, is due to a deficit of mass, or low-density roots, below sea level.
As told here:
Isostasy (Greek, isos: equal, stasis: standstill) in earth science is used as a concept of the gravitational equilibrium that explains the balance of topographical undulations on the Earth’s surface. The need to achieve natural balance or isostasy takes place on Earth wherever a large amount of weight is present. This weight might be due to a large mountain, ice from an ice age or even from human structures such as the weight from large man made lakes
The mountains can reduce the power of quakes but also send them to certain places, making them more powerful than expected.
As told here:
Mountain thermostats: scientists discover surprising climate stabilizer that may be key to the longevity of life on Earth.