Answer:
Tephra is formed by Volcanic Eruptions.
Step-by-step 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.