If you are looking at the distribution area even closer, it is found that these regions, which have no continuous geological surface, coincident with the former known trade centers of the 9th - 14 Century.
Kung ikaw ay naghahanap sa lugar ng pamamahagi kahit na mas malapit, ito ay natagpuan na ang mga rehiyong ito, na may hindi tuloy-tuloy na geological ibabaw, nagkakatulad sa dating kilalang sentro ng kalakalan ng 9th-14th na siglo.