<p>The Amaranto tephra is a pyroclastic sequence comprising three pumice-fallout layers in the central-eastern portion of the Michoacán-Guanajuato Volcanic Field, México. Its deposits are widely distributed in the northern part of Morelia city and are stratigraphically intercalated with other Miocene-Pleistocene volcanic units, making it an excellent regional stratigraphic marker. The three tephra layers exhibit a symmetrical gradation structure, mainly composed of pumice fragments, lithics, and loose crystals. Componentry analysis reveals the presence of gray and white pumice populations with a mineral paragenesis of plagioclase, amphibole, and Fe-Ti oxides, with vesicularity values between 71 and 79 vol.%, and densities between 0.6 and 0.8&#xa0;g/cm³. Both lithology and stratigraphic position suggest that the three layers have a common source coinciding with the Cañada-Coeperio graben in the eastern Zacapu basin. Likewise, the 1.47&#xa0;Ma ⁴⁰Ar/³⁹Ar radiometric age, stratigraphy, lithological components, and petrography support the occurrence of the three phases within a single eruption. Isopach and isopleth maps indicate that the eruption had a southeastern dispersion, covering an area of 824–831&#xa0;km², resulting in a total tephra volume of 17.6&#xa0;km³ (dense rock equivalent, 7&#xa0;km³). The eruptive phases had column heights of 21–26&#xa0;km, indicating Plinian eruptions, and were influenced by wind speeds &gt; 30&#xa0;m/s. An emission rate of the order of 6.27 × 10^7 to 1.47 × 10^8&#xa0;kg/s and a total duration of 48.7&#xa0;h were calculated. The Amaranto tephra represents an atypical eruption in the monogenetic Michoacán-Guanajuato Volcanic Field, and although highly explosive, large-volume eruptions are not frequent in the Morelia region, they pose a significant hazard for the population living in neighboring areas. A future plinian eruption in this densely populated region would severely affect more than 1 million inhabitants.</p>