tephra that is finer than 2 mm in diameter is called volcanic ash.
tephra that is finer than 2 mm in diameter is called?
volcanic ash
volcanic ash consists of fragments of pulverized rock, minerals and volcanic glass, created during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. the term volcanic ash is also often loosely used to refer to all explosive eruption products (correctly referred to as tephra), including particles larger than 2 mm. volcanic ash is formed during explosive volcanic eruptions when dissolved gases in magma expand and escape violently into the atmosphere. the force of the escaping gas shatters the magma and propels it into the atmosphere where it solidifies into fragments of volcanic rock and glass. ash is also produced when magma comes into contact with water during phreatomagmatic eruptions, causing the water to explosively flash to steam leading to shattering of magma. once in the air, ash is transported by wind up to thousands of kilometers away.
volcanic ash
when large amounts of tephra accumulate in the atmosphere from massive volcanic eruptions (or from a multitude of smaller eruptions occurring simultaneously), they can reflect light and heat from the sun back through the atmosphere, in some cases causing the temperature to drop, resulting in a temporary "volcanic winter". tephra mixed in with precipitation can also be acidic and cause acid rain and snowfall. 





























section::::classification.





























tephra fragments are classified by size:





























bullet::::- ash – particles smaller than 2 mm (0.08 inches) in diameter





























bullet::::- lapilli or volcanic cinders – between 2 and 64 mm (0.08 and 2.5 inches) in diameter
tephra