Rich volcanic soil makes the Po and Tiber river valleys ideally suited for agriculture. Historian Mike Anderson notes that volcanic ash made the soil near Rome some of the best in all of Europe. Rome attracted new settlers during its rise to power due to its agricultural potential, according to Collins Hill High School teacher Julie Smith. The Roman population grew quickly, thanks to surplus production of grains, olives, and other crops. The extra population later helped Rome's military expansion by providing a large supply of troops. The surplus also helped Rome to establish trade ties with other Mediterranean powers, enhancing the city's economic might. what is some cuases a d effects on this passage?​