Rock and Fossil Record Review

What geologic process is constantly occurring?

an arrangement of rock layers 

evidence of past life preserved by geologic processes

How many half lives have passed if 1/8 of the original isotope remains in the rock sample?

principle stating that the oldest rock layers are on the bottom

remains of the actual organisms - bones, teeth, shells etc.

method of determining whether an event is older or younger

organisms with hard parts such as bones, teeth are preserved more easily in the fossil record

any part of a previous rock layer, like a piece of stone, is older than the layer surrounding 

time needed for half of an unstable isotope sample to undergo radioactive decay

How many half-lives have passed if 1/32 of the original isotope remains in the rock sample?

process of radioactive parent isotopes breaking down into stable daughter isotopes

layers or parts of layers may be missing - often due to erosion

a thin film of carbon residue preserved as a fossil

a dinosaur footprint, nest, burrow, animal track are all examples of body fossils

sedimentary layers extend sideways in all directions until they thin out or reach a barrier

All of the fossils that exist provide us with a record of the history of the Earth.

evidence of the activities of past organisms

atoms of an element having a  different number of neutrons

fossils of organisms that only lived a short geologic time-span

The scientific study of past life, often times using fossils

method of measuring the actual age in years of an event or object

most fossils are formed when organisms are buried quickly by sediment

an event such as an intrusion or fault that is younger than the layers it passes through

What is letter "I"?

What is evidence that a fault has occurred?

An isotope has a half life of 50 million years. How old is it if 4 half lives have passed?

organisms with soft parts are preserved more easily in the fossil record