The igneous feature formed when magma forces its way into layers parallel to the surrounding rock layers is called a sill.

Here's a breakdown:

* Sills are tabular (flat) intrusions of igneous rock that are concordant, meaning they are parallel to the existing rock layers.

* They form when magma is injected into a zone of weakness, such as a bedding plane, within the existing rock.

* Sills can range in size from thin sheets to massive bodies extending for miles.

* They are often distinguished by their horizontal orientation and the fact that they are "sandwiched" between layers of older rock.

Let me know if you'd like to learn more about igneous intrusions!