organic texture . A sedimentary texture resulting from the activity of organisms, e.g., bioturbation.
GeoWord of the Day
The GeoWord of the Day is a free service of the American Geosciences Institute. All of the terms and definitions are from the Glossary of Geology, 5th Edition Revised.
glaucophane-schist facies . The facies (set of metamorphic mineral assemblages) in which mafic rocks are represented by combinations of sodic amphibole (e.g., glaucophane, crossite), lawsonite, sodic pyroxene, aragonite, epidote, and garnet. The mineral pair jadeite + quartz is also diagnostic. Exact definitions of the facies and its subdivisions vary (Turner, 1968). It represents lower temperatures and higher pressures than the greenschist facies. It is characteristic of metamorphism in subduction zones, with their unusually low geothermal gradients. Syn: blueschist facies.
orthometric elevation . The distance of a point above the geoid expressed in linear units measured along the plumb line at the point. Orthometric corrections are applied to measurements of precise leveling because level surfaces at different elevations are not parallel. Cf: height [geodesy].
rotation twin . A crystal twin whose symmetry is formed by apparent axial rotation of 180°. Cf: reflection twin.
phytal (phy'-tal). Said of those parts of a body of water that are shallow enough for the growth of rooted green plants. Cf: aphytal.
till billow . An undulating or swelling accumulation of glacial drift irregularly disposed with regard to the direction of movement of the ice (Chamberlin, 1894b, p.523).
thermistor chain (therm'-is-tor). A series of temperature-measuring instruments spaced along a cable or line and used to measure the vertical gradient of seawater temperature.
wet loose avalanche . A loose snow avalanche which involves wet snow.
swash zone . The sloping part of the beach that is alternately covered and uncovered by the uprush of waves and where longshore movement of water occurs in a zigzag (upslope-downslope) manner.
magnitude [volc] . The total volume of erupted material (Walker, 1980). Syn: eruption magnitude.
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