Tephrochronology dating range


“They’re based on ‘it’s that old because I say so,’ a popular approach by some of my older colleagues,” says Shea, laughing, “though I find I like it myself as I get more gray hair.”

In 2004 the Ediacaran Period of the latest Precambrian was defined in similar fashion, and was the first such newly designated period in 130 years; but earlier periods are simply defined by age.

The main lagoon measures about 7 square miles (20 km 2 ) and until 1932 was covered in thick glacial ice. Then the glacier started to retreat, and nowadays more than 300 feet (100 m) of ice breaks away each year to reshape the lagoon and fill it with spectacular icebergs.


Tephrochronology dating range

Tephrochronology dating range