Scientists can examine certain chemicals in some rocks, called isotopes, to learn how long ago the rocks formed and how old the fossils in, or associated with, those rocks are.
(some rocks; called; isotopes) (the fossils; associated; with) (those rocks; are; ) Context(those rocks are,List([160, 175))):(Scientists; can examine; certain chemicals; L:in some rocks; to learn how long ago the rocks formed and how old the fossils in, or associated with) Context(Scientists can examine those rocks are,List([0, 175))):(Scientists; can examine certain chemicals to learn; how long ago the rocks formed and how old the fossils in, or associated with) Context(Scientists can examine to learn those rocks are,List([0, 175))):(the rocks; formed; T:how long ago)
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certain chemicals L:in some rocks to learn how long ago the rocks formed and how old the fossils in, or associated with
how long ago the rocks formed and how old the fossils in, or associated with
T:how long ago