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Why Are Alpine Lakes So Blue?

Sometimes, when you see a photo of somebody’s national park trip, it’s too easy to tell how they’ve edited the colors. The greens are too vibrant, the rocks look like they came out of a movie and not a park, and they somehow have the exact right amount of sun on their face. Lakes, too, often look incredibly bright and turquoise blue, instead of the muddy green/brown that most of use are familiar with. They look something like this:

But, what many people don’t know is that lakes like that one (Lake Louise in Canada, known as “Instagram Lake”) need no filter. That striking and seemingly impossible blue color is completely natural! So, what makes these lakes (usually at high altitudes) so darn blue?

What Makes Mountain Lakes So Blue?

The blue color of these lakes occurs naturally due to the weather cycle, of all things. More on that below. Blue alpine lakes require a certain set of conditions that aren’t common outside large mountain ranges but are quite frequent within them.

High Altitudes, Big Mountains

blue lake in a forest

First, mountains. A lake isn’t going to be this color blue (unless you’re in Bora Bora) without being in or below a mountain range. Whether it’s a small pond near the peak or a massive lake at the mountain’s feet, the lake and mountain have got to be good buddes.

The reason for the striking color of the world’s bluest lakes has more to do with where they’re located and how they’re formed. There may be a more scientific term, but I’m just going to use “alpine lakes” as a blanket term to describe them. Lakes that look like this are generally at high altitudes or at the base of tall mountains.

Peyto Lake, the bluest lake in Canada and one of the prettiest places on Earth, sits at about 6,000 feet above sea level. Peyto Lake and Lake Louise are both situated in the Canadian Rockies, a massive mountain range that towers over the rest of the continent. It also happens to be where nearly all the bluest lakes in North America are located. The Rockies are made of sandstone and limestone, rocks that erode over time- though it still takes millions of years.

Alpine lake with blue water
Peyto Lake, the bluest lake in Canada, located in Banff National Park.

Glaciers Are a Big Factor

The Rockies are also covered in glaciers. Without the glaciers, the lakes wouldn’t exist; snow and glacial melt are what these lakes are made of. The water that melts from the glaciers and seasonal snows heads downhill, gathering in some places and flowing all the way to rivers in others. That glacial melt is directly responsible for the creation of the blue green color that makes alpine lakes so stunning.

It’s All About Glacial Flour

Glacial Flour (sometimes called rock flour) is created by the immense pressure that massive glaciers put on the mountains they rest upon. The weight, combined with the extremely slow movement of the glaciers, grinds the rock into a dust that’s finer than sand. When snow and ice melt and head downhill toward glacial lakes, glacial flour is carried with it.

The rock flour settles into these alpine lakes, even as meltwater flows further down the mountains and winds up in rivers. When the sun hits these lakes, it’s like somebody flips a switch- deep blue waters suddenly turn radiant turquoise, a spectacular blue green display that feels almost impossible to believe. The glacial flour that is suspended in the water reflects the sunlight with a sparkling brilliance that dazzles the eyes and captures the imagination.

Glacial peak in the mountains
Glaciers like this grind down the rock, sending rock flour into glacial lakes below.

Which National Park Has the “Bluest” Lake?

The answer to this question depends greatly on the season, the weather, and personal bias, but many people agree that Grinnell Lake in Montana’s Glacier National Park is the bluest lake in the US. Its blue green color and remarkable mountains make it an absolute must-see when you’re in Wyoming.

Grinnell Lake in Montana

Wrapping Up

Alpine lakes, even without the mystery of their color, are a sight to see. Whenever you’re near one, you can’t help but wonder at how the tiny particles of glacial flour reflect the light of the sun. What’s your favorite alpine lake? Let us know in the comments below!

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