In the western and southern parts of the Izu Peninsula, widespread deposits from ancient submarine volcanic eruptions are found. After a long era of submarine volcanism, the whole of Izu uplifted and emerged onto land, and subsequent erosion sculpted the landscape we see today, allowing us to view beautiful internal structures that would originally have remained buried underground. Among the submarine volcanic deposits, volcanic ash and pumice that settled on the seafloor preserved features such as bedding and, over long periods, lithified into rock. These stones became valued as a soft, easily worked, and heat-resistant building material known as Izu stone, and until around the early Showa period they were quarried and shipped from various parts of Izu. Muroiwa Cave was a quarry that operated from the Edo period until 1954 (Showa 29), and it remains one of the few places where visitors can see the site largely as it was in those days.