In 1980, Mount St. Helens, a volcano in the state of Washington in the United States, erupted and left only the remnants of a forest and a layer of nutrient-rich ash. What biological event followed the Mount St. Helens eruption?

      The biological event that followed the Mount St. Helens eruption is called biological succession.

Explanation:

       What happens in this process is that, once a biome, or a specific place gets destroyed, all this organic matter that it's left of it will be on the ground, and this can be the basis of another community that can grow exponentially in this place. Once the main events of the eruption pass, what happens is that, plants will start growing up again in some time, and this will happen until the point that this community gets to its climax again in some years.

all these collisions do one thing, and that thing is explained in the last option. when dusst, rocks and ice collide, they harden and form giant layers of rocks or hard ice.

d)   to harden materials to form different parts of earth’s layers

hope it ,

bioteacher101