Lake Colors in New Zealand

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Text, Earth Watch, Exploring the Blue Planet by Satellite
 
Lake Colors on the South Island of New Zealand. Earth Observatory, earthobservatory.nasa.gov, Operational Land Imager, Landsat 8 Satellite.
 
This natural-color satellite image of New Zealand's South island shows several large lakes with strikingly different colors.
 
May 20, 2019. Lake Hawea and Lake Wanaka. Two appear dark blue. The color is related to the vegetation that lines the valleys and rivers that feed these lakes.
 
Vegetation produces organic matter and other substances that darken the water.
 
Lake Pukaki, Lake Takapo, Lake Ohau, Lake Benmore. The light, turquoise-colored lakes are fed by Rivers flowing from large, active glaciers grinding through rocky valleys.
 
As the glaciers flow downstream, they pulverize rocks along the valley floors and walls.
 
The process produces a fine-grained powder of silt and clay known as glacial flour that is carried to the lakes in the meltwater streams.
 
Because the particles are so fine, they are slow to sink to the bottom, remaining suspended in the water column instead.
 
When sunlight hits the water, the glacial flour absorbs the shortest wavelengths: purples and indigos.
 
The water absorbs the longer wavelengths: reds, oranges, and yellows.
 
The remaining blues and greens are scattered back to the satellite.
 
Satellite images like this allow researchers to compare late colors across broad areas to better understand relationships between the lake's color, its composition, and its environment.
 
To learn more, go to: earthobservatory.nasa.gov