The interval of geologic time between approximately 56 and 34 million years ago.

The location on the surface of the earth directly above the earthquake.

A unit of geologic time usually lasting hundreds of millions of years. Eras are divided into smaller units of geologic time called periods.

The wearing away, breaking down, or dissolving of rock and other material by wind or water. The eroded material is often carried off and deposited in other areas. Types of erosion include solution, corrosion, and abrasion. Most limestone and gypsum caves are formed mainly by solution. Shelter caves and many sandstone caves are formed by abrasion.

A steep slope or cliff.

The seaward end or widened funnel-shaped tidal mouth of a river valley where freshwater comes into contact with seawater and where tidal effects are present.

Process of liquid water becoming water vapor, including vaporization from water surfaces, land surfaces, and snow fields, but not from leaf surfaces. Compare with transpiration.

A sedimentary rock made up mostly of minerals deposited when a saline solution (such as seawater) evaporates. Gypsum, salt, and anhydrite are evaporites left behind when ancient Kansas seas dried up.

(a) The change of a group of related organisms toward adaptation to the environmental conditions to which they have been exposed with the passage of time. (b) The theory that life on Earth has developed gradually, from one or a few simple organisms to more complex organisms.