isochron

/ (ˈaɪsəʊˌkrɒn) /

noun

a line on an isotope ratio diagram denoting a suite of rock or mineral samples all formed at the same time. The slope of the line is related to the age of the rock or mineral suite
a line or curve on a geological map or cross section (esp of oceanic crust) connecting points of identical age

QUIZZES

TAKE THIS QUIZ TO SEE WHAT YOU KNOW ABOUT HIGH SCHOOL PUNCTUATION!

Commas mark divisions in sentences. Periods end declarative sentences. Apostrophes show possession. Easy, right? Well, punctuation can get pretty tricky—fast. Think you got what it takes to be a punctuation expert? Take our quiz to prove it!
Question 1 of 10
Which of the options below is the best punctuation for the sentence? It__s your turn to pick the movie __ but your sister gets to pick the board game we _ re going to play.
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012