Page 45 - The Restless Earth Fossils

44 Fossils

These shells are rich with calcium and were constructed by single-
celled marine animals called foraminifera. The shells have pores
through which the animals could extend their pseudopodia (or
“false feet”) in order to catch food. Deposits of foraminifera like
these are the key component of limestone.

could fossils—or anything else—help provide concrete numbers
with which to mark points in deep time, even if those numbers
might be unimaginably large? Such numbers could provide an
absolute time scale.

Just hoW old are you, Mother earth?
Various people had observed that as you travel deeper into mines,
the temperature goes up. Many people thought that perhaps the
Earth burned like a glowing cinder, gradually cooling off after a
fiery birth. It seemed reasonable to physicists in the nineteenth

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