Figure 2.07. Geotherm with peridotite melting conditions. The variation of temperature with depth in the upper mantle is shown, with depth increasing downward. The contours between the solidus and liquidus are percent melt from experiments by Takahashi and others (1993). When you mouseover this image, the P-T path followed by convecting mantle beneath rifts is shown by a dashed line. On this path, convecting mantle crosses the peridotite liquidus boundary at a depth of about 40 km and begins to melt.