Volcanic plug

A volcanic plug is a volcanic landform created when lava hardens within a vent on an active volcano. A plug can cause an extreme build-up of pressure if magma is trapped behind it, and this can sometimes lead to a devastating eruption.

Often, erosion leads to the disappearance of the surrounding rock, while the erosion-resistant plug remains. An example of a landform created in this way is Chimney Rock, in Nebraska.