The river cuts through sandstones, limestones and some dolostones. But the culprit for the beautiful blue is the limestone! Limestone is composed primarily of calcium carbonate (CaCO3) and is white in color. As the river breaks down this rock into tiny crystals, these crystals will get mixed up into the water.

The striking blue-green color of Niagara Falls is a result of the immense power of the water and the unique geological composition of the Great Lakes basin. As the water flows over the falls, it carries with it a high concentration of "rock flour"—extremely fine-grained particles of limestone, shale, and sandstone that have been ground down by the grinding action of the river and glaciers over thousands of years. When sunlight hits the water, these suspended minerals scatter the light, particularly the shorter blue and green wavelengths, creating the vibrant hue known as "Niagara Green." Additionally, the depth of the Niagara River contributes to the intensity of the color; deeper water absorbs more red light, leaving the blue-green spectrum to be reflected back to the eye. The sheer volume of the water—over 6 million cubic feet per minute—also creates millions of tiny air bubbles which enhance the brightness of the water by reflecting even more light, giving the falls their signature crystalline and powerful appearance that has captivated visitors for centuries.