Cerro Macá is a relatively small volcano with a volume of only 39 cubic kilometres (9.4 cu mi).[5] It has a summit elevation of approximately 2,300 m above sea level[1][2] and features glaciers[6] that in 2011 covered an area of 27.62 square kilometres (10.66 sq mi).[7] The edifice is partially eroded[8] and a sector collapse is probably the origin of a large steep sided depression in the summit area.[9]Pyroclastic cones with associated lava flows are found on its southwestern flank[10] but also on the other slopes of the volcano, as far down as sea level and in the Bahia Aysen.[9]
1,440 ± 40 calibrated radiocarbon years ago a moderate explosive eruption deposited the MAC1 tephra,[5] which reaches thicknesses of 10–15 centimetres (3.9–5.9 in) 70 kilometres (43 mi) east of Macá.[8] Ash from past eruptions has been tentatively identified close to Cochrane Lake.[11] A more recent eruption occurred from the Bahía Pérez cinder cone on the southwestern flank in 1560 ± 110 years.[3]
In the early 20th century volcanic activity was observed at Ensenada Pérez, close to the southwestern flank of Macá.[10]
^ abThe elevation given here is from SRTM data and independently confirmed by ASTER GDEM. Elevations around 3,000 m given by other authorities should be discounted. The contours around the summit are missing from official Chilean topographic mapping.
^Masiokas, Mariano H.; Rivera, Andrés; Espizua, Lydia E.; Villalba, Ricardo; Delgado, Silvia; Aravena, Juan Carlos (October 2009). "Glacier fluctuations in extratropical South America during the past 1000years". Palaeogeography, Palaeoclimatology, Palaeoecology. 281 (3–4): 242–268. Bibcode:2009PPP...281..242M. doi:10.1016/j.palaeo.2009.08.006. hdl:10533/130935. ISSN0031-0182.
^ abD'Orazio, M; Innocenti, F; Manetti, P; Tamponi, M; Tonarini, S; González-Ferrán, O; Lahsen, A; Omarini, R (August 2003). "The Quaternary calc-alkaline volcanism of the Patagonian Andes close to the Chile triple junction: geochemistry and petrogenesis of volcanic rocks from the Cay and Maca volcanoes (~45°S, Chile)". Journal of South American Earth Sciences. 16 (4): 219–242. Bibcode:2003JSAES..16..219D. doi:10.1016/S0895-9811(03)00063-4. ISSN0895-9811.