E
eccentric
Noncircular; elliptical (applied to an orbit).

eccentricity
A value that defines the shape of an ellipse or planetary orbit; the ratio of the distance between the foci and the major axis.

eclipse
The cutting off of light from one celestial body by another.

ecliptic
The plane of Earth's orbit about the Sun

effusive eruption
A relative quiet volcanic eruption which puts out basaltic lava that moves at about the speed one walks. The lava is fluid in nature. The eruptions at the Kilauea volcano on the island of Hawaii are effusive

Einstein, Albert 1879-1955
German-American physicist. Einstein developed the Special and General Theories of Relativity, which along with Quantum Mechanics, forms the foundation of modern physics.

ejecta
Material such as glass and fragmented rock thrown out of an impact crater during its formation.

ellipse
An oval. Johannes Kepler first discovered that the orbits of the planets are ellipses, not circles; he based his discovery on the careful observations of Tycho Brahe.

en echelon fissures
Fissures that are parallel in trend to each other, but offset to either the left or right.

eolian
Related to wind deposits and associated effects.

eruption
The ejection of volcanic materials (lavas, pyroclasts and volcanic gases) onto the surface, either from a central vent, a fissure or a group of fissures.

explosive eruption
A dramatic volcanic eruption which throws debris high into the air for hundreds of miles. The lava is low in silicate and can be very dangerous for people near by. An example is Mount St. Helens in 1980.