Plural form; instances or types of geognosis, the knowledge or scientific study of the composition and structure of the Earth.
From Greek 'geo-' (earth) and 'gnosis' (knowledge). The plural maintains the Greek form rather than Anglicizing to '-es'.
Geognosis is essentially 'Earth knowledge'—it's the systematic study of what Earth is made of and how it's arranged, which was incredibly important before we had seismology and modern geology.
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