Final answer:
The structural organization of the paragraph is cause and effect as it explains how the availability of iron technology led to empires expanding their territories and creating a new social order.
Step-by-step explanation:
The structural organization of the paragraph from the section 'Iron forges social relationships' is Cause and effect. The paragraph explains how the availability of iron technology helped empires expand their territories and develop larger armies, which in turn created a new social order. Rulers then had to build infrastructure and establish government systems to manage their empires. All these events are connected in a cause and effect relationship.