1.3 A volcano is formed when magma reaches the Earth's surface

A volcano is any place where magma erupts onto the Earth's surface, or has been known to erupt in the past several million years. As well as lava, an erupting volcano also produces ash and volcanic gases.

Source: Earle, S (2015) Physical Geology#Chapter 4 Volcanism

Previous: 1.1 Magma is molten rock within the Earth's crust

See: 1.1a Lava is magma that has emerged onto the Earth's surface for the difference between magma and lava

Deeper: 1.3b classification of volcanoes depends on shape, eruption style and magmatic composition for different types of volcano

Deeper: 1.3a Volcanoes are most often found at plate boundaries and 1.3a1 Volcanoes can form away from plate boundaries over hot spots for locations of volcano formation