In contrast to an old ash-flow deposit,an old ash-fall tuff does NOT include which of the following?

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Ash-fall tuffs are formed from ash that falls from the sky and accumulates on the ground. They are typically thin and evenly bedded, and they may contain layers that become coarser-grained toward the base. Ash-fall tuffs can coat hills and valleys, and they may be welded to black obsidian. However, they do not typically show differences in thickness based on valleys and hills.

In Contrast to an Old Ash-Flow Deposit,an Old Ash-Fall Tuff