that scientists consider unlikely to erupt again because the volcano no longer has a magma supply. Examples of extinct volcanoes are many volcanoes on the Hawaiian – Emperor seamount chain in the Pacific Ocean (although some volcanoes at the eastern end of the chain are active), Hohentwiel in Germany, Shiprock in New Mexico, US, Capulin in New Mexico, US, Zuidwal volcano in the Netherlands, and many volcanoes in Italy such as Monte Vulture. Edinburgh Castle in Scotland is located atop an extinct volcano, which forms Castle Rock. Whether a volcano is truly extinct is often difficult to determine. Since "supervolcano" calderas can have eruptive lifespans sometimes measured in millions of years, a caldera that has not produced an eruption in tens of thousands of years may be considered dormant instead of extinct. Volcanic-alert level The three common popular classifications of volcanoes can be subjective and some volcanoes thought to have been extinct have erupted again. To help prevent people from falsely believing they are not at risk when living on or near a volcano, countries have adopted new classifications to describe the various levels and stages of volcanic activity. Some alert systems use different numbers or colors to designate the different stages. Other systems use colors and words. Some systems use a combination of both. Decade volcanoes The Decade Volcanoes are 16 volcanoes identified by the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) as being worthy of particular study in light of their history of large, destructive eruptions and proximity to populated areas. They are named Decade Volcanoes because the project was initiated as part of the United Nations-sponsored International Decade for Natural Disaster Reduction (the 1990s). The 16 current Decade Volcanoes are: Avachinsky-Koryaksky (grouped together), Kamchatka, Russia Nevado de Colima, Jalisco and Colima, Mexico Mount Etna, Sicily, Italy Galeras, Nariño, Colombia Mauna Loa, Hawaii, US Mount Merapi, Central Java, Indonesia Mount Nyiragongo, Democratic Republic of the Congo Mount Rainier, Washington, US Sakurajima, Kagoshima Prefecture, Japan Santa Maria/Santiaguito, Guatemala Santorini, Cyclades, Greece Taal Volcano, Luzon, Philippines Teide, Canary Islands, Spain Ulawun, New Britain, Papua New Guinea Mount Unzen, Nagasaki Prefecture, Japan Vesuvius, Naples, Italy The Deep Earth Carbon Degassing Project, an initiative of the Deep Carbon Observatory, monitors nine volcanoes, two of which are Decade volcanoes. The focus of the Deep Earth Carbon Degassing Project is to use Multi-Component Gas Analyzer System instruments to measure CO2/SO2