Sombrero Uplift Above the Altiplano-Puna Magma Body: Evidence of a Ballooning Mid-Crustal Diapir

Rise and Subside Earth's surface tends to deform as magmatic fluids rise toward the surface from below, usually manifesting itself in uplift of continental crust. Fialko and Pearse (p. 250; see the Perspective by Brooks), however, show that subsidence, or widespread sinking, accompanies uplift when magma rises. Satellite measurements reveal that the massive Altipano-Puna magma body in the central Andes balloons upward, causing subsidence around the region of uplift, resembling a sombrero. Melting of surrounding rocks as the magma rises likely withdraws material and causes the subsidence. Subsidence accompanies uplift below a massive rising magma body in the central Andes mountains. The Altiplano-Puna ultralow-velocity zone in the central Andes, South America, is the largest active magma body in Earth’s continental crust. Space geodetic observations reported an uplift in the Altiplano-Puna proper at a rate of ~10 mm/year; however, the nature of the inferred inflation source has been uncertain. We present data showing that the uplift has persisted at a nearly constant rate over the past two decades, and is surrounded by a broad zone of subsidence. We show that the ongoing uplift and peripheral subsidence may result from a large mid-crustal diapir fed by partial melt from the Altiplano-Puna Magma Body.