Earth's History Crossword

amount of time required for half of an original sample of radioactive material to decay or undergo radioactive transformation.
Any method of measuring the age of an event or object in years.
A break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time.
Any method of determining whether an event or object is older or younger than other events or objects.
process in which a radioactive isotope tends to break down into a stable isotope of the same element or another element.
fossil that is used to establish the age of a rock layer because the fossil is distinct, abundant, and widespread and the species that formed the fossil existed for only a short span of geologic time.
remains or traces (whole or part) of past plant and animal life that has been preserved in sedimentary rock.
very long period of time the Earth has existed.
stable element into which a radioactive element breaks down.
states that in layers of sedimentary rocks, younger rocks normally lie on top of older rocks if the layers have not been disturbed.
idea that geologic processes that occurred in the past can be explained by current geologic processes.
fossilized mark that formed in sedimentary rock by the movement of an animal on or within soft sediment.
atom of a substance that has the same number of protons but a different number of neutrons as another atom of the same substance.
method of determining the absolute age of an object by comparing the relative percentages of a radioactive parent isotope and a stable daughter isotope.
historical sequence of life indicated by fossils found in layers of Earth's crust.
process by which a unstable nucleus gives off nuclear radiation.
ordered arrangement of rock layers that is based on the relative ages of the rocks and in which the oldest rocks are at the bottom.
permanent disappearance of a species.
layers of sedimentary rocks.
igneous rock formed when magma forces its way into sedimentary rock and hardens below or on the Earth's surface.