Clay, Coal and Sand do not come in sufficient quantity to sustain most any map beyond preliminary T4 forays.
We get to noodle around for a little while, then everything goes dry, except that dang mountain of iron over there.
Usually well before we get a chance to complete a largescale terraforming project.
The Trading Post has been generous to a few players, but the majority do not enjoy the same privilege, so it is not a viable alternative.
Adding a zero to the end of each value for Clay, Coal and Sand, so that a 1,000 node becomes 10,000 and so on, will go a long way to ensuring that the communities we build will be workable and accessible well into the future.