The difference between tephra and tuff is that ____________.
A) tephra is created in ash falls, whereas tuff is created in pyroclastic flows
B) tephra is unlithified, whereas tuff is lithified
C) tephra is always silicic, whereas tuff is always basaltic
D) all of the above

Question

Quizplus · Accepted Answer

Tephra and tuff are both volcanic materials, but tephra refers to fragments of volcanic material that have been ejected from a volcano and have not yet been lithified (i.e. turned into rock), while tuff refers to lithified deposits of volcanic ash, tephra, and other pyroclastic material. Therefore, tephra is unlithified, while tuff is lithified. Choice A is not entirely accurate, as tuff can also be created by ash falls settling on the ground and becoming lithified over time. Choice C is also incorrect, as neither tephra nor tuff has to be exclusively silicic or basaltic in composition.

The Difference Between Tephra and Tuff Is That ____________