The polar mountains are volcanic in origin.

This is a structure similar to Olympus Mons on Mars. A Gigantic shield volcano. Lower gravity and/or higher viscosity lava could be responsible for the height. Given the lack of really any features related to plate tectonics, it stands to reason that the planet has another tectonic regime, which allowed the shield volcanic to build up for eons. Maybe Io-like lid tectonics or delamination and upwellings like Venus might have. Both regimes could in theory support a carbon cycle.

Another solution, though it is close to the first would be that we are dealing with a large igneous province. Floodvolcanism like the Siberian or Deccan traps can build up basaltic highlands to several kilometers. The Siberian Traps rise the land in the area of current Siberia by 2 to 3 kilometers.

The polar mountains are volcanic in origin.

This is a structure similar to Olympus Mons on Mars. A Gigantic shield volcano. Lower gravity and/or higher viscosity lava could be responsible for the height. Given the lack of really any features related to plate tectonics, it stands to reason that the planet has another tectonic regime, which allowed the shield volcanic to build up for eons. Maybe Io-like lid tectonics or delamination and upwellings like Venus might have. Both regimes could in theory support a carbon cycle.

Another solution, though it is close to the first would be that we are dealing with a large igneous province. Flood volcanism like the Siberian or Deccan traps can build up basaltic highlands to several kilometers. The Siberian Traps raise the land in the area of current Siberia by 2 to 3 kilometers.

The polar mountains are vulcanic in origin.

This is a structure similar to Olympus Mons on Mars. A Gigantic shield vulcano. Lower gravity and/or higher viscosity lava could be responsible fo the hight. Given the lack of really any features related to plate tectonics, it stands to reason that the planet has another tectonic regime, which allowed the shield vulcanic to build up for eons. Maybe Io-like lid tectonics or delamination and upwellings like Venus might have. Both regimes could in theory support a carbon cycle.

Another solution, though it is close to the first would bd that we are dealing with a large ignious province. Floodvulcanism like the Siberian or Deccan traps can build up basaltic highlands to several kilimeters. The Siberian Traps rise the land in the area of current Siberia by 2 to 3 kilometers.

The polar mountains are volcanic in origin.

This is a structure similar to Olympus Mons on Mars. A Gigantic shield volcano. Lower gravity and/or higher viscosity lava could be responsible for the height. Given the lack of really any features related to plate tectonics, it stands to reason that the planet has another tectonic regime, which allowed the shield volcanic to build up for eons. Maybe Io-like lid tectonics or delamination and upwellings like Venus might have. Both regimes could in theory support a carbon cycle.

Another solution, though it is close to the first would be that we are dealing with a large igneous province. Floodvolcanism like the Siberian or Deccan traps can build up basaltic highlands to several kilometers. The Siberian Traps rise the land in the area of current Siberia by 2 to 3 kilometers.