Earth's History Crossword

The central or innermost portion of the Earth.
A large, bowl-shaped cavity in the ground or on the surface of a planet.
The outermost layer of the Earth.
Materials or substances such as minerals, forests, water, and fertile land that occur in nature and can be used for economic gain.
The theory that the solar ans stellar systems were developed from a primeval nebula.
A length or portion of time.
Of, relating to, or denoting the period before written records.
Belonging to the very distant past and no longer in existence.
Any of the pieces of hard, whitish tissue making up the skeleton in humans and other vertebrates.
A combustible black or dark brown rock consisting mainly of carbonized plant matter, found mainly in underground deposits and widely used as fuel.
The gradual movement of the continents across the earth's surface through geological time.
(of a species, family, or other larger group) having no living members.
A natural fuel such as coal or gas, formed in the geological past from the remains of living organisms.
Any of the almost spherical concentric regions of matter that make up the earth and its atmosphere, as the lithosphere and hydrosphere.
The rigid outer part of the earth, consisting of the crust and upper mantle.
A layer of natural material.
A supposition or a system of ideas intended to explain something, especially one based on general principles independent of the thing to be explained.
The action or process of adapting or being adapted.
The variability among living organisms from all sources.
(of organic matter) rot or decompose through the action of bacteria and fungi.
An amount or layer of a substance that gradually develops in a particular place.
A fossil reptile of the Mesozoic era, often reaching an enormous size.
The process by which different kinds of living organisms are thought to have developed and diversified from earlier forms during the history of the earth.
Develop gradually, especially from a simple to a more complex form.
The remains or impression of a prehistoric organism preserved in petrified form or as a mold or cast in rock.
The science that deals with the earth's physical structure and substance, its history, and the processes that act on it.
The process whereby organisms better adapted to their environment tend to survive and produce more offspring.
A process for determining the age of an object by measuring the amount of a given radioactive material it contains.
The order in which sedimentary strata are superposed one above another.
An element, feature, or factor that is liable to vary or change.