A ledge
The continental shelf layer is called the shelf break. It is the steepest part of the continental shelf where the seafloor drops off sharply towards the deeper ocean floor.
A narrow passage through land is called a gorge.
A narrow valley with 4 letters is called a "rift."
A narrow furrow is typically referred to as a groove. It can also be called a trench or a rut, depending on the context in which it is used.
A narrow field of study within a larger field is often called a sub-discipline.
A ledge.
A ledge
The edge is called the shelf break. The actual declining shelf is called the called the continental slope.
A long, narrow and curled bone shelf which protrudes into the breathing passage of the nose is called a turbinate, or better known in anatomy as a nasal concha.
shelf
This is because it is a narrow boat
A long narrow cut is called a slit.
The continental shelf layer is called the shelf break. It is the steepest part of the continental shelf where the seafloor drops off sharply towards the deeper ocean floor.
A wooded ravine is called a gully.
Some small narrow boats are called canoes, others are called kayaks.
Some small narrow boats are called canoes, others are called kayaks.
A long narrow racing boat is called a racing shell.