The top of Mount Rainier is white because it is covered in glacial ice and snow.

Here's why:

* Elevation: Mount Rainier is one of the tallest mountains in the Cascade Range, reaching over 14,400 feet. At such high elevations, the temperature is consistently below freezing, even during the summer months.

* Precipitation: The mountain receives heavy snowfall throughout the year, especially during the winter.

* Limited melting: While some snow melts during the summer, the amount of snowfall generally exceeds the amount of melting, leading to a constant accumulation of snow and ice.

This combination of factors creates a permanent ice cap and glaciers that cover the summit and upper slopes of Mount Rainier, giving it its distinctive white appearance.