Knowing that we have test plant with geothermal and the depth required is 6,4km even with laser drilling the effectiveness might not be so great.
It might end up cheaper to ship in ammonia synthesized from solar in the tropics. Most likely it will be a combination of several: normally, delivery by transmission line because cheapest, but with geothermal held ready for strategic backup, and stockpiled ammonia for load peaks.
Shipping will get cheaper as fuel does, but is already astonishingly cheap.
I’m not aware of any significant and serious efforts to replace ships with a green fuel, and they comprise a huge percentage of our emissions.
The west-African coastal Sahara, coastal Peru/Bolivia, Baja California, Arabia/Sudan/Eritrea, Yemen/Oman/Pakistan, Socotra, and north-western Australia all look like good places to site solar-driven ammonia synthesis. I don't doubt that less geographically-favored sites will dominate instead.