A sill is formed.
if it squeezes into a fault, its a dike, if it squeezes between horizontal layers, its a sill
sill
A sill is a slab of volcanic rock formed when magma squeezes between layers of rock. It is typically horizontal and parallel to the surrounding rock layers. Sills are distinguishable from dikes, which cut across the rock layers.
A Sill is formed
The magma that squeezes into vertical cracks between rocks and then hardens is called a dike. Dikes are tabular bodies of igneous rock that cut across the existing rock layers.
If vertical, a dyke; if horizontal, a sill.
sill
It forms a sill.
The slab that forms when magma forces itself across rock layers is called a dike.
Yes, a dike forms when magma intrudes into existing rock layers and solidifies. As the magma cools and solidifies underground, it creates a vertical or near-vertical sheet-like body of igneous rock that cuts across the existing rock layers.
If the magma forces itself along a plane that is parallel to the bedding or foliation planes of the rock strata then (in other words it squeezes between two existing layers) it is a sill. If however it cuts across the bedding or foliation planes it is a dyke. For more information, please see the related links.
The magma forms sills and magma chambers.