1. Fossil Sedimentary Rock Mold Cast Petrified Fossil
A trace of an ancient organism that has been preserved in rock
Sedimentary Rock
A type of rock that forms when particles form other rocks or the remains of plants and animals are pressed and cemented together
Mold
A fossil formed when an organism buried in sediment dissolves leaving a hollow area
Cast
A fossil that is a copy of the organism’s shape formed when minerals seep into the mold
Petrified Fossil
A fossil in which minerals replace all or part of the organism

2. A well tested concept that explains a wide range of observations
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
Paleontologist
A scientist who studies fossils to learn about organisms that lived long ago
Scientific Theory
A well tested concept that explains a wide range of observations
Evolution
The process by which all the different kinds of living things have changed over time

3. Extinct Relative Age Absolute Age Law of Superposition Extrusion
Describes a type of organism that no longer exists on the Earth
Relative Age
The age of a rock compared to the ages of rock layers
Absolute Age
The age of a rock given as a number of years since that rock formed
Law of Superposition
The geologic principle that states that in horizontal layers of sedimentary rock each layer is older than the one above it and younger than the one below
Extrusion
An Igneous rock layer formed when lava flows onto the Earth’s surface and hardens

4. Intrusion Fault Unconformity Index Fossil Atom
An igneous layer formed when magma hardens beneath the Earth’s surface
Fault
A break or crack in Earth’s lithosphere along which rocks can move
Unconformity
A place where an old eroded rock surface is in contact with a newer rock layer
Index Fossil
Fossils of widely dispersed organisms that lived during only one short period
Atom
The smallest particle of an element

5. Element Radioactive Decay Half Life Geologic Time Scale Era
A substance in which all the atoms are the same and cannot be broken down into other substances
Radioactive Decay
The breakdown of a radioactive element releasing particles and energy
Half Life
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 the Earth’s history
Era
One of the three long units of geologic time between the Precambrian and Present

6. Period Comet Continental Drift Invertebrate Vertebrate
One of the units of geologic time into which geologists divide eras
Comet
A loose collection of ice, dust and small rocky particles typically with a long narrow orbit of the Sun
Continental Drift
The hypothesis that the continents slowly move across Earth’s surface
Invertebrate
An animal without a backbone
Vertebrate
An animal with a backbone

7. Amphibian Reptile Mass Extinction Mammal
A vertebrate that lives part of its life on land and part of its life in water
Reptile
A vertebrate with scaly skin that lays eggs with tough leathery shells
Mass Extinction
When many types of living things become extinct at the same time
Mammal
A warm blooded vertebrate that feeds its young milk