A volcanic arc lies in the Carpathians. In its southern segment, also known as the Călimani (Kelemen) - Gurghiu (Görgényi) - Harghita (Hargita) chain, volcanism has migrated between 9 and 0.22 million years ago southward, forming a c. long volcanic chain. Magma output progressively decreased during time, with early volcanoes being large stratovolcanoes sometimes featuring caldera-forming eruptions, while more recent activity includes monogenetic volcanoes although more precise dating and volume estimation efforts at Ciomadul have found an increase of eruption rates over time.