The preserved remains or traces of living things.
A scientist who studies fossils to learn about organisms that lived long ago.
The type of rock that is made of hardened sediment
A fossil in which minerals replace all or part of an organism.
A fossil formed when an organism buried in sediment dissolves, leaving a hollow area.
A fossil that is a copy of an organism's shape, formed when minerals seep into a mold.
A type of fossil consisting of an extremely thin coating of carbon on rock.
A type of fossil that provides evidence of the activities of ancient organisms
A well-tested concept that explains a wide range of observations.
The process by which all the different kinds of living things have changed over time.
Describes a type of organism that no longer exists anywhere on Earth.
The age of a rock compared to the ages of rock layers.
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 layer above it and younger than the layer below it.
A place where an old, eroded rock surface is in contact with a newer rock layer.
A break or crack in Earth's lithosphere along which the rocks move.
An igneous rock layer formed when magma hardens beneath Earth's surface.
An igneous rock layer formed when lava flows onto Earth's surface and hardens.
Fossils of widely distributed organisms that lived during only one short period of time.
The smallest particle of an element.
A type of matter in which all the atoms are the same.
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.
One of the three long units of geologic time between the Precambrian and the present.
An animal without a backbone.
One of the units of geologic time into which geologists divide eras.
Subdivisions of the periods of the geologic time scale.
An animal with a backbone.
A vertebrate that lives part of its life on land and part of its life in water.
A vertebrate with scaly skin that lays eggs with tough, leathery shells.
When many types of living things become extinct at the same time.
A warm-blooded vertebrate that feeds its young milk.