What best explains how tephra deposit forms

Tephra is formed by Volcanic Eruptions.

Explanation:

During a Volcanic eruption along with Magma sometimes rock fragments are also ejected into atmosphere which are called Tephra. Tephra is deposited around the Volcano depending on its size. Bigger fragments travel less while smaller fragments can be deposited a little far to the volcano. Variation in Tephra material results in variety of Structures.