Diablo Lake formed when the Seattle Light Department completed Diablo Dam in the Skagit River Gorge in 1928. The Diablo Dam supplies up to 159,000 kilowatts of power. Even though Diablo Lake is a new lake, geologically speaking, it is a fine example of a glacial lake.
As glaciers in the surrounding high country slowly wear down the mountains, the grinding of rock against rock produces a fine silt that meltwater streams carry into the lake below. This rock flour is what gives the lakes their unusual colors. Diablo Lake receives the flow of many glaciers, including North Cascades National Park's largest, Boston Glacier high on the flanks of 8,845-foot Mount Forbidden. The rock flour consists of clay-sized particles of rock created by glacial erosion or by artificial grinding to a very small size. The particles are so small that they remain suspended in the water. The minerals that form this glacial flour are typically ground up quartz and feldspar.
Ross Lake and Lake Diablo are both glacial lakes that are good examples of this phenomenon. In the summer, they both have very surreal, distinct colors. Ross Lake is more of a blue and Lake Diablo a turquoise color. This is because the sunlight scatters through the floating particles of glacial rock flour. Green-blue wavelengths of light reflect, while other colors are absorbed. Visible light - that which is detectable by the human eye - consists of wavelengths ranging from approximately 780 nanometers to 390 nanometers .
Specific wavelengths within the spectrum correspond to a specific color based upon how humans typically perceive light of that wavelength. The long wavelength end of the spectrum corresponds to light which is perceived by humans to be red and the short wavelength end of the spectrum corresponds to light which is perceived to be violet. Other colors within the spectrum include orange, yellow, green and blue. The graphic below depicts the approximate range of wavelengths which correspond with the various perceived colors within the spectrum.
The colors perceived of objects are the results of interactions between the various frequencies of visible light waves and the atoms of the materials which objects are made of. The color you see is actually the color reflected by the glacial flour. The frequencies of light which become transmitted or reflected to our eyes will contribute to the color which we perceive.
Water entering Thunder Arm of Diablo Lake is just hours away from its glacial source. The deep, cold water cannot support an abundance of plant and animal life. Fish and other aquatic organisms are typically found near the outflow of side streams, where food and nutrients are washed into the lake and sun rays penetrate shallow depths.
If you are interested in more info on the natural wonders of the you can follow this link to the official National Park Site area North Cascades Institute's environmental learning center on the lake offers many day and overnight outdoors programs. You can learn more at: ncascades.org or call 360-856-5700, ext. 209.
To claim this cache you must email me the answers to these questions about the lake through my geocaching.com.
1. What gives Diablo Lake such a striking color? (Don't think too hard, I just want to make sure you are paying attention.)
2. If you had to guess by looking at the lake and the chart, what would be the wavelength of the light that is the majority of light being reflected back from Diablo Lake?
3. Post a picture of yourself with your GPSr unit near the coordinates with a view of Diablo Lake (to prevent arm-chair caching!)