Final answer:
The Juan de Fuca Plate and the North American Plate form a convergent boundary where deep earthquakes typically occur, related to the subduction process forming the Cascade Range.
Step-by-step explanation:
The boundary between the Juan de Fuca Plate (JF) and the North American Plate (NA) along the west coast of North America is a convergent boundary. This type of boundary is formed when two tectonic plates move towards each other, with one sliding beneath the other into the Earth's mantle. This process is known as subduction, which results in deep earthquakes within the subduction zone. In the case of the Juan de Fuca Plate, it is slowly subducting under the North American Plate, leading to the formation of the Cascade Range, including volcanic mountains such as Mt. St. Helens. Due to the subduction process, most earthquakes along this boundary are deep, typically occurring at depths of 30 to 70 kilometers below Earth's surface. However, they can sometimes reach even greater depths.