Name: What Causes the Bright Turquoise Color of Glacial Lakes? GEO GIRL
Uploaded: 2026-01-07T21:01:20.000Z
Duration: 3 min 46 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

The water in this lake is so turquoise, it almost looks fake, but it is in fact real.

Typically, lakes are greenish brown or even dark blue.

But this lake, Garibaldi Lake in British Columbia, is certainly not a typical lake color.

So what is causing this bright turquoise color?

Well, it's not that there's some strange mineral dying the lake,

it's actually a combination of geology and physics that causes this color.

The the secret lies in the glaciers you see feeding into the lake.

When glaciers grind down mountains, they don't just carve valleys,

they also pulverize rock into very fine powder called glacial flour.

These tiny particles are smaller than sand or silt, often just microns across.

And streams carry this glacial flower into Garibaldi Lake

as meltwater flows down from the glaciers up in the taller mountains surrounding the lake.

But here's the key: Those particles don't settle quickly.

Instead, they stay suspended in the water column, scattering light in a very specific way.

When sunlight hits the lake, the suspended glacial flour scatters the shorter wavelengths of visible light, the blues and the greens, back toward our eyes,

while the longer wavelengths like reds and yellows, are absorbed.

That's why instead of muddy mucky water, we see this incredible turquoise glow.

And fun fact, this is the same effect that causes the color of many lakes across glaciated mountain,

like those in the Canadian Rockies, Alaska and even some in Iceland.

But importantly, not all glacial lakes are bright turquoise like this.

And it turns out, it's because the type or composition of the rock that gets grinded into the flour matters.

Silica-rich felsic rocks like granite and granitic gneiss produce light colored fine quartz and feldspar-rich flour,

which reflects light very effectively, resulting in bright turquoise to milky blue lakes.

Whereas those with lower silica content, like intermediate to mafic volcanic andesite and basalt,

tend to make darker iron and magnesium-rich flour, which absorbs more light,

making lakes that look greener, grayish or duller blue, depending on concentration.

And lastly, carbonate rocks like limestone or dolostone yield whitish flour.

Sometimes producing chalky aqua or jade green tones.

So because the glaciers feeding Garibaldi Lake grind up both felsic rocks like granite from the coast plutonic complex that I talked about a couple videos ago, and

intermediate to mafic volcanic rocks like basalts and andesites from Mount Price, Black Tusk and other lava flows,

this results in a very quartz and feldspar-rich glacial flower with some more silica-poor volcanic materials,

which are light enough to strongly scatter blue and green light, but

also fine enough to stay suspended for long periods of time.

And this leads to Garibaldi's vivid but not opaque turquoise color.

As climate warms and Garibaldi's glaciers retreat,

they'll produce less meltwater and less glacial flour.

And over the centuries, as the glaciers vanish, Garibaldi Lake's iconic turquoise may fade into a more ordinary blue.

So come see this beautiful lake before its gorgeous blue color fades away.

But keep in mind the hike up to Garibaldi Lake is 18km and straight uphill, so be prepared.

And be sure to check out the others I made recently about the geology of this area.

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What Causes the Bright Turquoise Color of Glacial Lakes? GEO GIRL

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