How it works
Individual ice is mostly transparent. In a snowbank, countless air-ice boundaries reflect and refract light repeatedly before it returns to the viewer.
What people often miss
Deep snow or compressed ice can look blue because light travels farther and red wavelengths are absorbed more strongly. Dirt and algae can add other colors.
Why this question comes up
The color comes from the structure of accumulated crystals rather than a white pigment.
Key points
- Snow looks white because its many ice crystals scatter visible wavelengths in many directions, combining the colors into white light.
- Individual ice is mostly transparent. In a snowbank, countless air-ice boundaries reflect and refract light repeatedly before it returns to the viewer.
- Deep snow or compressed ice can look blue because light travels farther and red wavelengths are absorbed more strongly. Dirt and algae can add other colors.
Bottom line
Snow looks white because its many ice crystals scatter visible wavelengths in many directions, combining the colors into white light.
Source and verification
This Answer was checked against National Snow and Ice Data Center. Follow the source for the full official explanation and any later updates.