Final answer:
The troposphere's top is about 7 to 8 miles above Earth's surface, where temperatures decrease with altitude and where most weather events and human activities occur.
Step-by-step explanation:
The top of the troposphere is an average of about 7 to 8 miles (11-13 km) above Earth's surface. This atmospheric layer is where virtually all human activities take place and where weather phenomena occur.
The temperature in the troposphere decreases as the altitude increases, reaching its coldest point at the boundary with the stratosphere, known as the tropopause. Beyond the troposphere, the stratosphere extends from about 6 miles (10 km) to 31 miles (50 km) in altitude, and this is where most commercial airplanes fly.