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The preserved remains or traces of living things


A fossil that is solid copy of an organism's shape, formed when minerals seep into a mold

Petrified Fossil

A fossil in which minerals replace all or part of an organism

Carbon Film

A type of fossil consisting of an extremely thin coating of carbon on rock

Trace Fossil

A type of fossil that provides evidence of the activities of ancient organisms


A scientist who studies fossils to learn about organisms that lived long ago


Describes a type of organism that no longer exists anywhere on Earth

Relative Age

The age of a rock compared to the ages of rock layers

Absolute Age

The age of a rock given as the number of years since the rock formed

Law of Superposition

The geologic principle that states that in horizontal layers of sedimentary rock, each layer is older than the layers above it and younger than the layer below it


An igneous rock layer formed when lava flows onto Earth's surface and hardens


An igneous rock layer formed when magma hardens beneath Earth's surface


A break or crack in Earth's lithosphere along which the rocks move


A place where an older, eroded rock surface is in contact with a newer rock layer

Index Fossil

Fossils of widely distributed organisms that lived during only one short period


The smallest particle of an element

Radioactive Decay

The breakdown of a radioactive element, releasing particles and energy


The time it takes for half of the atoms of a radioactive element to decay

Geologic Time Scale

A record of the geologic events and life forms in Earth's history

How long ago did Earth form?

4.6 billion years ago

What is the first division of Earth's history called?

Precambrian Era

What force caused a ball of dust, rock, and ice to be pulled together to form Earth?


List the 3 eras of Earth's history in order from oldest to youngest

Paleozoic Era Mesozoic Era Cenozoic Era

What percentage of a radioactive element remains after 2 half-lives?


12.5% of a radioactive element remains. How many half-lives have passed?


Carbon-14 has a half-life of 5730 years. How many years will it be until 50% of the Carbon-14 remains?

5730 years

When carbon-14 undergoes radioactive decay, it turns into....


When potassium-40 undergoes radioactive dating, it turns into...


If you find a fossil that is 4 billion years old, you should use what kind of radioactive dating?

potassium-argon dating

Rock A is older than Rock B but younger than Rock C. Is this an example of absolute age or relative age?

Relative Age

You find a rock that is 4380 years old. Is this an example of absolute age or relative age?

Absolute Age

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