Volcanoes can be constructive if they happen in the ocean, as they can form islands and therefore be new places for plants and animals to grow and thrive.
Volcanoes can be destructive if they kill a large amount of animals by forming on land.
A volcano can destroy trees and buildings, but at the same time it can form islands and piles of rock. A river slowly washes away pieces of a rock, but at the same time it deposits the rock somewhere else and creates a new formation. Hope this helps !
