Easy Trail
A trail of less than four miles round trip and with less than a 2,000 foot elevation gain. Round trip hiking time is generally 45 minutes to 3 hours, but inexperienced hikers may take longer.

Ecology
The study of the relationships of living things or groups of living things to their environment.

Ecological Niche
That special place in a community occupied by a living thing. Where it lives, where it gathers food, where it seeks shelter.

Ecosystem
An ecological unit consisting of interrelationships between animals, plants, and their environment.

Ecotone
A transition zone between two ecological communities, where species overlap.

Ectotherm
Cold-blooded; body temperature responds directly to the temperature of the surrounding environment.

Emergent
An aquatic plant with its lower part submerged and its upper part extending above water.

Endemic
Restricted to a geographic region.

Endotherm
Warm-blooded; internal regulation.

Ensolite
A soft rubber material that makes wonderfully light yet, for the most part, comfortable sleeping mats for use under sleeping bags while backpacking or camping.

Entopic
When discussing rock art, this type represents images presumably seen during a shaman's trance. Usually abstract in design.

Eolian
Deposited by wind.

EPA
Environmental Protection Agency.

Ephemeral Stream
A stream that flows occasionally in direct response to precipitation or snow melt.

Erastra
Grinding stone used in grain mills and mining operations, often turned by horses or mules.

Ergot
A fungus infecting the fruiting bodies of numerous grasses. Ergot preparations have been used medicinally for several hundred years, but many human and animal deaths have been recorded from eating ergot infected grain.

Erosion
The group of related processes by which rock is broken down physically and chemically and the products removed from any part of the Earth's surface. It includes the processes of weathering, solution, corrosion, and transportation.

Escarpment
The steep face frequently presented by the abrupt termination of stratified rocks. See also Scarp.

ESIA
Eastern Sierra Interpretive Association

Evaporite Minerals
Those minerals which are deposited as a result of the evaporation of water.

Evergreen
Plants that bear green leaves year-round; not deciduous.

Exoskeleton
A supporting structure on the outside of the body, enclosing all living cells.

Exposed Trail
This refers to a route where there is little danger of falling, but, if you do fall, there is a risk of serious injury. Crossing ledges or ridge crests with a precipitous drop below causes a feeling of being exposed to danger.

External Frame Pack
The name "external" comes from the rigid metal or molded plastic frame attached to the outside of the pack bag. Advantages traditionally include superior ventilation and a more natural upright walking stance.

Extrusive Rock
Rock formed from lava or other volcanic material ejected onto the surface of the earth.