Fig. 4. Sills may develop into magma chambers. This sometimes happens when a single, thick sill receives magma frequently enough so as to stay liquid and expand into a chamber. Sometimes, however, a cluster of sills, such as the one seen here (Tenerife, Canary Islands), may merge into a magma chamber. The sills seen here, however, clearly did not develop into a magma chamber (cf. Gudmundsson, 1990, 2011, cited).