A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes Earth and other terrestrial planets, as well as the processes that shape them. Geologists usually study geology, earth science, or geophysics, although backgrounds in physics, chemistry, biology, and other sciences are also useful. Field research is an important component of geology, although many subdisciplines incorporate laboratory and digitalized work. Geologists can be classified in a larger group of scientists, called geoscientists.
The Geologist by Carl Spitzweg, c. 1860
Scotsman James Hutton, father of modern geology
"Geologists at work" from the U.S. Geological and Geographic Survey of the Territories (1874 - 06/30/1879). Photographer: William Henry Jackson
A young geologist learns about flow banding
A terrestrial planet, telluric planet, or rocky planet, is a planet that is composed primarily of silicate, rocks or metals. Within the Solar System, the terrestrial planets accepted by the IAU are the inner planets closest to the Sun: Mercury, Venus, Earth and Mars. Among astronomers who use the geophysical definition of a planet, two or three planetary-mass satellites – Earth's Moon, Io, and sometimes Europa – may also be considered terrestrial planets. The large rocky asteroids Pallas and Vesta are sometimes included as well, albeit rarely. The terms "terrestrial planet" and "telluric planet" are derived from Latin words for Earth, as these planets are, in terms of structure, Earth-like. Terrestrial planets are generally studied by geologists, astronomers, and geophysicists.
The inner planets (sizes to scale). From left to right: Earth, Mars, Venus and Mercury.
Sizes of Kepler planet candidates based on 2,740 candidates orbiting 2,036 stars as of 4 November 2013 (NASA)
Artist's impression of a carbon planet
Geysers erupting on Enceladus