Final answer:
The Phoenix metropolitan area has experienced rapid growth due to factors like climate, economy, and land availability, resulting in a population surpassing 4 million people and subsequent urban challenges.
Step-by-step explanation:
The rapid population growth in the Phoenix metropolitan area has been significant, making it one of the largest metropolitan areas in the United States. With an increase to over 4 million inhabitants, understanding the factors contributing to this expansion can provide insights into urban development, economic factors, and the challenges faced due to such growth.
The area's attractive climate, robust economy, and availability of land have been key drivers behind the expansion. Additionally, the influx of new residents has brought challenges such as increased demand for infrastructure, housing, and services, as well as environmental concerns.