Answer:
relating to, consisting of, or denoting fragments of rock erupted by a volcano.
Explanation:
Pyroclastic rocks are clastic rocks composed of rock fragments produced and ejected by explosive volcanic eruptions. The individual rock fragments are known as pyroclasts. Pyroclastic rocks are a type of volcaniclastic deposit, which are deposits made predominantly of volcanic particles.
It is impossible to build a drainage system on the outside of the Sao Francisco river as buildings are built on the outside of the foundation.
The Subarnarekha is developing a small drainage system.
The Amazon basin is the largest drainage basin in the world.
The Urugay drainage system includes the greater part of southeastern Brazil, Paraguay, southeastern Bolivia and northern Argentina
So i would suggest putting the Amazon as it is the most common known and largest. Remember to use geographical terms!
