1. The ratio between the area of an inscribed circle to the area of a circumscribed circle fitted to the outline of the crest of a crater (see CRATER (2)). For fresh lunar craters, the average circularity index reaches a maximum value of about 0.85–0.90 for craters about 10 km in diameter.
2. See DRAINAGE BASIN SHAPE INDEX.
"circularity index." A Dictionary of Earth Sciences. . Encyclopedia.com. (January 16, 2019). https://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/circularity-index
"circularity index." A Dictionary of Earth Sciences. . Retrieved January 16, 2019 from Encyclopedia.com: https://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/circularity-index