Assessment Questions 13.8

1. What environmental factor is suggested to have contributed to the collapse of Uruk, the world's first city, around 5,000 years ago?

A sharp increase in dust blowing off the land and onto the sea in the Gulf of Oman suggests a relentless drought in Mesopotamia around 5,000 years ago, severely impairing Uruk's agriculturally based economic system.

2. How did the Moche civilization respond to the drying up of their primary irrigation channels around 600 C.E.?

Instead of collapsing, the Moche civilization responded to the drying up of their irrigation channels by rapidly shifting to sites farther inland and adjacent to rivers with more dependable water sources for irrigation.

3. In relation to current sea level changes, how much has the mean global sea level risen since the late 1800s, and what is the consensus on future sea level changes by the year 2100?

Since the late 1800s, the mean global sea level has risen by about 20 cm (8 in). The consensus is that it will continue to rise an additional 30 to 120 cm (between 12 and 48 in) by the year 2100.