A geological event in which magma does not form lava is called intrusion.

Here's why:

* Lava is molten rock that has erupted onto the Earth's surface.

* Magma is molten rock that is still beneath the Earth's surface.

Intrusion occurs when magma pushes its way into existing rock layers but doesn't reach the surface. This can create various geological formations, including:

* Batholiths: Large, irregularly shaped intrusions of igneous rock that cool slowly deep underground.

* Sills: Sheet-like intrusions that are parallel to the surrounding rock layers.

* Dikes: Sheet-like intrusions that cut across existing rock layers.

* Laccoliths: Dome-shaped intrusions that push the overlying rock layers upward.

So, while magma is involved in intrusion, it never reaches the surface to become lava.