The Quill is a large dominantly andesitic stratovolcano that forms the SE end of St. Eustatius (Statia) Island. It was formed about 32,000-22,000 years ago by rhyolitic eruptions on a shallow-water limestone bank 3 km offshore of a 200,000 year old volcanic center exposed at the NW end of the island. The interaction of rhyolitic magma with seawater produced pyroclastic-surge deposits, rich in limestone fragments, that joined the two islands and cover the entire slopes of the volcano. The surges also swept across the older island and incorporated carbonized plant remains, shell fragments, and remains of fossil hermit crabs. A likely cryptodome tilted up limestones at Sugarloaf on the southern coast. A steep-sided crater, 760 m wide and more than 300 m deep, caps The Quill; a notch on the western crater rim has directed the youngest pyroclastic flows towards the island's capital, Orangestad. The last dated eruption produced pyroclastic flows about 1,600 years ago.