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What is Cryptotephra?

Tephra (Shards and pyroclastic material) are deposited “geologically’ instantaneously over large areas.  A tephra layer or horizon provides a time Line—an isochron—that can be used to precisely date the enclosing sediment.


Tephra is formed by the fragmentation of magma in the volcanic vent by bursting bubbles. The bubbles are related to volatile exsolution as magma rises to lower pressures in the vent.


SEM image of pumice showing bubbles and bubble walls.  Broken bubble walls form shards.

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Shards from a tephra unit in the northern McCullough Range just south of Las Vegas.

While coarser tephra is deposited about the volcano, shards are injected into the atmosphere and carried by atmospheric winds over great distances.

There are two main types of tephra deposits.  Those that form visible beds and tephra (mainly shards) that are not visible in the stratigraphic section--Tephra not visible in the sedimentary or volcanic section that requires specialized processing to identify is cryptotephra!

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What is CLAGR?

CLAGR is the Cryptotephra Laboratory for Archaeological and Geological Research located in the Lilly Fong Geoscience Building at UNLV. The lab specializes in the processing and analysis of extremely low abundance cryptotephra from sediments to provide precise dates for archaeological and geological events. The laboratory was established in 2013 to support an international effort to understand the evolution of early modern humans in southern Africa. CLAGR is funded by a grant from the National Science Foundation Archaeometry Program.

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