Fossils Vocab

Across
3.	A long cylinder of ice obtained from drilling through ice caps or ice sheets
6.	The scientific study of an origin, history and structure of earth and the process that shape earth
7.	The trace or remains of an organism that lived long ago, most commonly preserved in sedimentary rock
9.	The time required for half of a sample of a radioactive isotope to break down by radioactive decay to form a daughter isotope
10.	The weather conditions in an area for a long period of time
12.	Any method of determining whether an event or object is older or younger than other events or objects.
13.	A principle that states younger rocks lie above older rocks if the layers have not been disturbed
14.	A fossilised structure, such as a footprint or a coprolite, that formed in sedimentary rock by animal activity on or within soft sediment
15.	An ordered arrangement of rock layers that is based on the relative ages of rocks in which the oldest rocks are at the bottom

Down
1.	A break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time
2.	A principle that geological processes that occurred in the past can be explained by current geological processes
4.	The standard method used to divide Earth's long natural history into manageable parts
5.	Any method of measuring the age of an event or object in years.
8.	The process in which a radioactive isotope tends to break down isotope tends to break down into a stable isotope of the same element or another element
11.	A method of determining the absolute age of an object by comparing the relative percentages of a radioactive isotope