Answer:
B. TEPHRA
Explaination:
Tephra is the general term used by volcanologists for fragments of volcanic rock and lava of any size expelled from a volcano.
The term tephra defines all pieces of all fragments of rock ejected into the air by an erupting volcano. Most tephra falls back onto the slopes of the volcano, enlarging it. ... Shaded areas indicate where tephra layers remain from associated very large eruptions.
