The volcanic landform that is formed when the more resistant pipe remains after most of the cone has been eroded is called a volcanic neck or lava neck.

Here's why:

* Volcanic Pipe: The conduit through which magma travels from deep within the Earth to the surface during a volcanic eruption.

* Volcanic Cone: The cone-shaped structure built up by layers of lava and ash during eruptions.

* Erosion: Over time, the softer, less resistant materials that make up the volcanic cone are eroded by wind, water, and ice.

* Resistant Pipe: The volcanic pipe, often composed of harder, more resistant rock like solidified magma, remains standing after the cone is eroded away.

The resulting landform is a pillar or tower of rock, often quite striking, that stands as a testament to the former presence of a volcano.