Final answer:
A volcano is formed when magma reaches the surface and cools, creating new landmass.
Step-by-step explanation:
The geological feature that is formed when magma reaches the surface and cools, creating new landmass, is a volcano. When magma erupts from the Earth's mantle and reaches the surface, it forms a volcanic cone. As the magma cools and solidifies, it forms layers of volcanic rocks like basalt or andesite.
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