Final answer:
A volcanic neck is the remains of the hardened, igneous conduit through which magma once flowed to the surface of a volcano. It becomes visible after the surrounding, softer volcanic materials have been eroded away, offering a glimpse into the structure of the volcano's plumbing system.
Step-by-step explanation:
A volcanic neck is the remains of a volcano's conduit system. When surrounding softer materials like ash and tuff from the volcano's edifice are eroded away, the harder igneous core often remains standing. This hardened core represents the pathway that magma used to flow through to reach the surface during the active period of the volcano.
Volcanoes occur at mid-ocean ridges, subduction zones, and collision zones between continental plates, as well as above mantle hot spots. The volcanic neck is a geologic structure that gives us insight into the deep underground features of these volcanic regions, which are otherwise difficult to study.
One of the most famous regions for studying volcanic activity is the western margin of South America, particularly in the Central Andes Mountains, which showcases a history of subduction-related volcanism. Additionally, hot spots such as the one beneath Hawaii create volcanic islands and indicate plumes of heat rising from deep within the Earth's mantle independent of plate boundaries.