How often does the shape of Earth’s orbit change in the eccentricity cycle?

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Quaternary paleogeography — Quaternary Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the Quaternary Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.

The shape of Earth’s orbit, known as eccentricity, varies from nearly circular to elliptical. This change occurs with periodicities of 100,000 and 413,000 years.1

These variations are part of the Milankovitch cycles, which describe how predictable changes in Earth's orbital geometry influence the amount of solar radiation received by the planet. While eccentricity is one of the three primary orbital parameters—alongside axial tilt and precession—its specific 100,000-year cycle is a key focus in studies of geochronology and paleoclimate research regarding glacial-interglacial patterns.1234