The process by which animals or plants become suited to their environment.
Basalt
A dark­colored volcanic rock.
Cenozoic era
The fourth era of geologic time. It began about 65 million years ago and extends to the present.
Devils Canyon
Found in Colorado, USA.
Era
One of the intervals of geologic time based on changes in Earth's crust and life forms. The four geologic eras are Cenozoic, Mesozoic, Paleozoic, and Precambrian.
Erosion
The weathering of the Earth's surface by the action of water, wind, earthquakes and so on.
Excavate
Reveal or extract a fossil by digging.
Fissures
A split or crack in the Earth's surface, caused by tectonic activity.
Flood Plains
The flat land next to a river channel which covers with water when a river overflows its banks. As a result, river valley flood plains are built of river­carried sediments.
Fossil
Remains, or traces of, prehistoric animals and plants, usually preserved in rock. Trace fossils include such things as footprints and skin imprints.
Fossilization
Process of preservation by which the pores in bone become filled with minerals from the surrounding sediment, giving the bones a stone-­like appearance and weight.
Gastrolith
A stone which is swallowed to break up food and aid digestion. These stones become smooth and polished.
Geologic time scale
Divides all the time since the Earth began into named units based on geologic changes and sudden life-­form changes.
Geologist
A scientist who studies the Earth, its history, and the processes which shape it.
Gizzard
A special compartment of the stomach which has thick muscular walls. The muscles powerfully squeeze the gizzard's contents in a "chewing" action.
Gizzard stones
Animals with gizzards often eat small stones. The stones are squeezed together in the gizzard, mashing and grinding any food caught between them. In this way, vegetation is "chewed" and digested.
Igneous
Rock formed from molten magma which cools on or below the Earth's surface.
Longitudinal
Running lengthwise.
Matrix
The usually fine-­grained rock in which fossils are embedded.
Mesozoic era
The third era of geologic time which began about 225 million years ago and ended about 65 million years ago. It encompasses the Triassic, Jurassic, and Cretaceous periods.
Metamorphic
Either sedimentary or igneous rock which has been changed by the intense heat or pressure due to tectonic activity.
Paleontologist
A scientist who studies fossils and prehistoric life on Earth.
Paleozoic era
Began about 600 million years ago and ended about 225 million years ago. It is the second era of geologic time.
Peripheral
A type of vision which is caused by eyes which look in two different directions at the same time. Things are seen in only two dimensions. They look flat.
Permineralization
The process by which bones are made more dense by groundwater­deposited minerals.
Precambrian era
The oldest and first period of time, from Earth's formation 4.5 billion years ago to the beginning of life 600 million years ago.
Predator
An animal which naturally preys on other animals for food.
Prey
An animal that is hunted and killed by another for food.
Resonant
Echoing, or an area which reinforces or prolongs sounds by vibrations which occur at the same time.
Rills
A small stream, or a shallow channel formed in the surface of soil or rocks by running water.
Sedimentary
Rock formed when sand, mud or organic material are eroded by wind or water. The resulting sediments settle on Earth's surface, forming a layer. They can then condense into rock.
Stereoscopic
The result of eyes which look in the same direction at the same time. In the part of the vision field which is shared between both eyes, the image is seen in three dimensions, therefore it has depth and solidity.
Tectonic
Large plates of rock fit together to make Earth's crust. These are called tectonic plates. They shift around and grind against each other, causing not only earthquakes, but also Earth's surface to change shape.
