Page 92 - The Restless Earth Fossils

Glossary

▲

absolute time scale Time scale that is measurable in years.
agate Rock of mixed colors composed of silicon dioxide
(SiO ).
2
amber Fossilized tree sap (resin).
ammonite An extinct mollusk with a coiled shell.
angiosperms Flowering plants.
angular unconformity Two layers of rock at sharp angles
to one another.
anthropologists Scientists who study human physical and
cultural remains.
aragonite A form of calcium carbonate (CaCO ) used in shell
3
construction.
archaea Simple organisms that lived during the Archean Eon.
archaeologists Scientists who study human tools and other
artifacts.
archaic Extremely old.
archaic humans Group of humans that lived in Africa about
700,000 year ago.
archean eon Period of time from 4 to 2.5 billion years ago.
atomic clocks Radioactive elements whose decay rate can be
used to determine a fossil’s age.
Banded iron formation Group of Precambrian rocks with
high iron content.
Burgess shale Important early Cambrian fossil site in British
Columbia, Canada.

1

RE_Fossils2print.indd 91 3/17/09 9:00:54 AM