The phrase "a tephra" is correct and usable in written English.
It can be used when referring to a type of volcanic material that is ejected during an eruption, typically in geological or scientific contexts.
Example: "The geologist collected a sample of a tephra to analyze its composition and age."
Alternatives: "a volcanic ash" or "a pyroclastic material".
(a) Tephra thickness as a function of square root of area within each isopach, using fallout in the Faroe Islands, satellite data and the established first order behaviour of tephra thicknesses declining exponentially with distance from source3,37,38.
A tephra layer between Palaeosols 4 and 5 is interpreted from its geochemical fingerprint as the product of one of the mid-Holocene eruptions of Mt. Burney, located in the Southern Patagonian Andes.
a Tephra patches or spots.
A tephra thinning trend similar to the 2014 eruption was observed in the phreatic eruption at Ontake in 1979.
Other costs may also result directly or indirectly from a tephra (or any solid disaster waste) clean-up.
The increased content of volcanic glass above the E4 deposits (Fig. 7) suggests a tephra fall after the E4 sedimentation.
The unknown-a tephra at the bottom of Site U1429 is near the MIS 11/10 boundary.
From these data, we inferred that the To-a tephra fell between the E4 and E3 deposits, and we assigned the E4 deposits to the 869 Jogan tsunami.
The unknown-a tephra is found at three sites, and the unknown-b and unknown-c tephras occur only at Sites U1426 and U1427.
The age of the unknown-a tephra layer is 383 ka, above the distinct peaks of TWC indicators of MIS 11c (Fig. 7).
The Towada-a tephra (To-a) (AD915; Machida and Arai 2003) is a useful indicator of the 869 Jogan tsunami deposits in the Sendai and Ishinomaki Plains (Minoura and Nakaya 1991; Sawai et al. 2007; Shishikura et al. 2007).
