Why do fjord-gulfs have long narrow shapes?

Fjord-gulfs, or fjords, possess their characteristic long, narrow shapes because they are formed by the glacial erosion of mountain valleys.12

During the Pleistocene Epoch, massive glaciers descended from coastal mountains, carving deep, U-shaped valleys into the landscape. Because a glacier has high viscosity and a large cross-section, it tends to straighten and smooth its path, resulting in a valley that is significantly deeper and wider than those formed by rivers. These glaciers were so heavy and powerful that they eroded the valley floors far below sea level.134

When the glaciers eventually melted and sea levels rose, these deep, steep-walled troughs were inundated by the ocean, creating the long, narrow inlets known as fjords. Their elongated form is a direct reflection of the original glacial path through the mountainous terrain.132