St. Mary’s Islands, also known as Coconut Island and Thonsepar, are a group of four small islands in the Arabian Sea off the coast of Malpe in the Indian state of Karnataka. They are distinguished by the geological production of columnar rhyolitic lava. Scientific research indicate that the basalt of the St. Mary’s Islands was generated by sub-aerial subvolcanic activity because Madagascar was attached to India at the time. Madagascar rifted approximately 88 million years ago. Columnar rhyolite Lava is one of four geological monuments in Karnataka state, as well as one of the 34 National Geological Monuments of India designated by the Geological Survey of India in 2016 for its protection, maintenance, promotion, and enhancement of geotourism.