Rock flour

Rock flour, or glacial flour, consists of fine-grained, silt-sized particles of rock, generated by mechanical grinding of bedrock by glacial erosion or by artificial grinding to a similar size. Because the material is very small, it becomes suspended in meltwater making the water appear cloudy, which is sometimes known as glacial milk.[1][2]

When the sediments enter a river, they turn the river's colour grey, light brown, iridescent blue-green, or milky white. If the river flows into a glacial lake, the lake may appear turquoise in colour as a result. When flows of the flour are extensive, a distinct layer of a different colour flows into the lake and begins to dissipate and settle as the flow extends from the increase in water flow from the glacier during snow melts and heavy rain periods. Examples of this phenomenon may be seen at Lake Pukaki and Lake Tekapo in New Zealand, Lake Louise, Moraine Lake, Emerald Lake, and Peyto Lake in Canada, Gjende lake in Norway, and several lakes (among others, Nordenskjöld and Pehoé) in Chile's Torres del Paine National Park.

Rock flour from glacial melt enters headwaters at Lake Louise
Rock flour from glacial melt enters Lake Louise, Canada


Muru memurubu
Muru river pours rock flour into Gjende lake, Norway
Östra Blanktjärn Lake in Vålådalen Nature Reserve, Sweden

Typically, natural rock flour is formed during glacial migration, where the glacier grinds against the sides and bottom of the rock beneath it, but also is produced by freeze-and-thaw action, where the act of water freezing and expanding in cracks helps break up rock formations. Multiple cycles create a greater amount.

Although clay-sized, the flour particles are not clay minerals but typically ground up quartz and feldspar. Rock flour is carried out from the system via meltwater streams, where the particles travel in suspension. Rock flour particles may travel great distances either suspended in water or carried by the wind, in the latter case forming deposits called loess.

Agricultural use

Some agronomists believe that rock flour has a powerful effect in restoring trace minerals to soil. An early experimenter was the German miller, Julius Hensel, author of Bread from Stones, who reported successful results with steinmehl (stonemeal) in the 1890s. His ideas were not taken up due to technical limitations and, according to proponents of his method, because of opposition from the champions of conventional fertilisers.

John D. Hamaker argued that widespread remineralization of soils with rock dust will be necessary to reverse soil depletion by current agriculture and forestry practice.

While this originally was an alternative concept, increasing mainstream research has been devoted to soil amendment and other benefits of rock flour application: for instance, a pilot project on the use of glacial rock, granite and basaltic fines by the U.S. Department of Agriculture exists at the Henry A. Wallace Beltsville Agricultural Research Center. The SEER Centre in Scotland is a leading source of information on the use of rock dusts and mineral fines. The Soil Remineralization Forum was established with sponsorship from the Scottish Environment Protection Agency and has commissioned a portfolio of research into the benefits of using mineral fines. The Forum provides an interface among research, environmentalists, and industry.

See also


  1. ^ "Glossary of Terms: G: Glacial Milk"
  2. ^ Gornitz, Vivien (editor) (2007) "Glacial Geomorphology" pp. 361-374 Encyclopedia of paleoclimatology and ancient environments Springer Netherland, Berlin, page 365, ISBN 978-1-4020-4551-6

External links


Besseggen, or Besseggi, is a mountain ridge in Vågå kommune in Oppland county, Norway. Besseggen lies east in Jotunheimen, between the lakes Gjende and Bessvatnet.

The walk over Besseggen is one of the most popular mountain hikes in Norway. About 30,000 people walk this trip each year. The route over Besseggen starts at Gjendesheim, up to the trails highest point, Veslfjellet (1,743 m), down Besseggen, further over the relatively flat area Bandet (at the foot of Besshø), and ends at Memurubu, where one may take the regularly scheduled ferry route back to Gjendesheim. Many choose to do the hike in the other direction by starting at Memurubu after first taking the ferry there from Gjendesheim. The trip is estimated to take about 5–7 hours to walk without rest stops.

From Besseggen there is a great view over Gjende and Bessvatnet. One of the unique aspects of the view is that Gjende lies almost 400 m lower than Bessvatnet, and while Bessvatnet has a blue color typical of other lakes, Gjende has a distinct green color. The green color is the result from glacier runoff containing clay (rock flour). Looking down towards Memurubu one can see the nearby river Muru coloring the water with a light colored runoff.


Besshø (official form on maps: Besshøe), is a mountain in Vågå, Oppland, Norway, and is part of the Jotunheimen mountain range. It lies right above Bessvatnet, along the Besseggen hiking trail. On the mountain's north-eastern side a small cirque glacier, and is surrounded by a large ice-cored moraine, a relatively rare feature in Norway.

From Besseggen there is a nice view over Gjende and Bessvatnet. Gjende is about 400 m lower than Bessvatnet. While Bessvatnet has a blue colour common to lakes, Gjende has a green colour due to glacier runoff depositing clay into the lake (rock flour).

Cracker Lake

Cracker Lake is located in Glacier National Park, in the U. S. state of Montana. Located at the head of a canyon, the waters of Cracker Lake are an opaque turquoise from rock flour (silt) originating from Siyeh Glacier. To the south of Cracker Lake lies Mount Siyeh which rises more than 4,000 feet (1,200 m) above the lake. Cracker Peak to the southeast and Allen Mountain to the north are other prominent peaks nearby. Cracker Lake is a 6.1-mile (9.8 km) hike from the Many Glacier Hotel.

Delta Lake (Teton County, Wyoming)

Delta Lake is located in Grand Teton National Park, in the U.S. state of Wyoming. Delta Lake is situated in Glacier Gulch and is fed rock flour (glacial silt) from the Teton Glacier, which turns the water turquoise in appearance.

Emerald Lake (British Columbia)

Emerald Lake is located in Yoho National Park, British Columbia, Canada. It is the largest of Yoho's 61 lakes and ponds, as well as one of the park's premier tourist attractions. Emerald Lake Lodge, a high-end lodge perched on the edge of the lake, provides local accommodation. A 5.2 km (3.2 mi) hiking trail circuits the lake, the first half of which is accessible to wheelchairs and strollers. During the summer months, canoe rentals are available; in the winter, the lake is a popular cross country skiing destination.

The lake is enclosed by mountains of the President Range, as well as Mount Burgess and Wapta Mountain. This basin traps storms, causing frequent rain in summer and heavy snowfalls in winter. This influx of moisture works with the lake's low elevation to produce a unique selection of flora. Trees found here are more typical of B.C.'s wet interior forests, such as western red cedar, western yew, western hemlock and western white pine. The alluvial fan on the northeast shore produces wildflowers in abundance during late June and early July.Due to its high altitude, the lake is frozen from November until June. The vivid turquoise color of the water, caused by powdered limestone, is most spectacular in July as the snow melts from the surrounding mountains.

The first non-indigenous person to set sight on Emerald Lake was Canadian guide Tom Wilson, who stumbled upon it by accident in 1882. A string of his horses had gotten away, and it was while tracking them that he first entered the valley. The lake had an impression on even the most seasoned of explorers: "For a few moments I sat [on] my horse and enjoyed the rare, peaceful beauty of the scene." It was Wilson who gave the lake its name because of its remarkable colour, caused by fine particles of glacial sediment, also referred to as rock flour, suspended in the water. However, this was not the first time Wilson had dubbed a lake 'Emerald'. Earlier that same year he had discovered another lake which he had given the same moniker, and the name even appeared briefly on the official map. This first lake however, was shortly renamed Lake Louise.


Gjende (or Gjendin) is a lake in the Jotunheimen mountains in Norway's Jotunheimen National Park. The proglacial lake shows typical characteristics of glacial formation, being long and narrow, with steep walls—18 km in length and only 1.5 km in width at the broadest point. Gjende has a characteristic light-green color resulting from the large quantity of rock flour which is discharged into the Gjende by the Muru river. The river Sjoa provides the outlet from Gjende at Gjendesheim, and flows eastward into the Gudbrandsdalslågen river.

Gjende lies in the middle of Jotunheimen National Park and both to the north and south of the lake lie peaks greater than 2,000 m. There are numerous staffed tourist cabins maintained by the Norwegian Mountain Touring Association (DNT); in the west end lies Gjendebu, on the north side lies Memurubu and on the east end lies Gjendesheim. In the summer boats provide transport between these locations.

Glacial lake

A glacial lake is a body of water with origins from glacier activity. They are formed when a glacier erodes the land, and then melts, filling the depression created by the glacier.

Grinnell Lake

Grinnell Lake is located in Glacier National Park, in the U. S. state of Montana. Named after George Bird Grinnell, the lake has an opaque turquoise appearance from the rock flour (silt) which is transported to the lake from Grinnell Glacier. Grinnell Lake is accessible via the Grinnell Glacier Trail and is 3.2 miles (5.1 km) from the Many Glacier Hotel.

Joffre Lakes Provincial Park

Joffre lakes provincial park is a class A provincial park located 35 km east of Pemberton in British Columbia, Canada. It was established in 1988.

Three glacier-fed lakes are located in the park: Lower, Middle and Upper Joffre Lakes. The rock flour in the water reflects blue and green waves, and gives the lakes a turquoise colour. Joffre Lakes is a popular destination for hikers in the summer and mountain climbers in the winter due to its scenic lakes, glaciers and challenging peaks. In recent years the park's popularity has increased dramatically, creating controversy due to the volume of litter in the park and drivers parking dangerously on the adjacent provincial highway.

Lake Connecticut

Glacial Lake Connecticut formed over what is now Long Island Sound and coastal Connecticut at the fore edge of the ice sheet of the Wisconsin glaciation, as the lobe of the Laurentide Ice Sheet began to retreat, some 18 to 20,000 years before present. It was dammed by the terminal moraine that now forms the spine of Long Island and Fishers Island. About 15,000 BP, the moraine dam that impounded Lake Connecticut failed; the outlet, known as The Race for its tidal rip currents, lies between the North Fork of Long Island and Fishers Island. For a time, much of the lake bed was exposed to wind-driven erosion: the cue is found in soundings that reveal regional unconformities in the sediment bed of Long Island Sound.

The fore-edge lake formed by glacial meltwater expanded to be about the same size as present-day Long Island Sound; it may have been connected at times with similar freshwater lakes in Block Island Sound and Buzzards Bay, while sea level was low. The fairly shallow average depth of 78 feet (24 m) of today's Long Island Sound is the result of fine lake-bottom sediments deposited as glacial outwash slowed in Lake Connecticut. Suspended as rock flour, the fine sediments would have rendered Lake Connecticut a turquoise blue-green.

The end of Lake Connecticut was marked by a series of intervals of salt water incursion after about 15,000 BP and subsequent refreshening, as rising sea levels and isostatic rebound of land depressed by the former weight of ice sheets adjusted to one another.

Lake Louise (Alberta)

Lake Louise, named Lake of the Little Fishes by the Stoney Nakota First Nations people, is a glacial lake within Banff National Park in Alberta, Canada. It is located 5 km (3.1 mi) west of the Hamlet of Lake Louise and the Trans-Canada Highway (Highway 1).

Lake Louise is named after the Princess Louise Caroline Alberta (1848–1939), the fourth daughter of Queen Victoria and the wife of the Marquess of Lorne, who was the Governor General of Canada from 1878 to 1883.

The turquoise colour of the water comes from rock flour carried into the lake by melt-water from the glaciers that overlook the lake. The lake has a surface of 0.8 km2 (0.31 sq mi) and is drained through the 3 km long Louise Creek into the Bow River.

Fairmont's Chateau Lake Louise, one of Canada's grand railway hotels, is located on Lake Louise's eastern shore. It is a luxury resort hotel built in the early decades of the 20th century by the Canadian Pacific Railway.

Moraine Lake and Lake Agnes are also accessible from Lake Louise.

Lake Nooney

Lake Nooney is located in Glacier National Park, in the U. S. state of Montana. The lake is east of Mount Custer and .50 miles (0.80 km) west of Lake Wurdeman. The Herbst Glacier is located above the lake to the northwest. Rock flour (silt) from melting glaciers make the lake appear opaque turquoise in color.

Mistaya River

The Mistaya River is a short river in western Alberta, Canada. It flows through the Canadian Rockies, and a section of the Icefields Parkway was built along its course.

Mistaya River originates in Peyto Lake, a glacial lake of typical blue colour (due to rock flour). Mistaya flows north-west, receiving the waters of creeks such as Delta, Silverhorn, Cirque, Noyes, ChephrenTotem, Epaulette, Bison, Kaufmann and Sarback. A series of elongated lakes are formed along the river: Mistaya Lake and Waterfowl Lakes.

Mistaya merges into the North Saskatchewan River at Saskatchewan River Crossing.

From its headwaters of Peyto Creek, Mistaya River has a total length of 38 km.

The origin of the name is from the Cree language - "mistaya" meens a grizzly bear.

Moraine Lake

Moraine Lake is a glacially fed lake in Banff National Park, 14 kilometres (8.7 mi) outside the Village of Lake Louise, Alberta, Canada. It is situated in the Valley of the Ten Peaks, at an elevation of approximately 6,183 feet (1,885 m). The lake has a surface area of 50 hectares (120 acres).

The lake, being glacially fed, does not reach its crest until mid to late June. When it is full, it reflects a distinctive shade of azure blue. The unique colour is due to the refraction of light off the rock flour deposited in the lake on a continual basis by surrounding glaciers.


Muru is a river in Jotunheimen in southern Norway. It originates at the glacier Austre Memurubrean and runs through Memurudalen then finally empties into the lake Gjende right next to Memurubu. The river is approximately 10 kilometres (6 mi) long and is the primary source for the lake Gjende.

One of the unique aspects of Gjende is that the water has a distinct green color. The green color is the result from glacier runoff containing clay (rock flour). Looking down towards Memurubu one can see the river Muru coloring the water with a light colored runoff.

The river is used for kayaking. However there is no nearby road access and kayakers must carry their kayaks up the river.

Memurubu is a popular starting point for hikers wishing to travel across Besseggen.

Petersen Glacier

Petersen Glacier is in Grand Teton National Park, Wyoming, United States. The glacier is in a cirque to the west and above north Cascade Canyon at an altitude of approximately 10,000 feet (3,000 m). The glacier is named after Frank Petersen, one of the first mountaineers to climb Grand Teton in 1898. Runoff from the glacier is heavy in rock flour (glacial silt) which turns the waters of Mica Lake turquoise in appearance. The glacier is no longer visible in satellite imagery, indicating it may have disappeared. All of the existing glaciers in Grand Teton National Park were created during the Little Ice Age (1350-1850) and have been in a general state of retreat since the mid-19th century.

Peyto Lake

Peyto Lake ( PEE-toh) is a glacier-fed lake in Banff National Park in the Canadian Rockies. The lake itself is easily accessible from the Icefields Parkway. It was named for Bill Peyto, an early trail guide and trapper in the Banff area.The lake is formed in a valley of the Waputik Range, between Caldron Peak, Peyto Peak and Mount Jimmy Simpson, at an elevation of 1,860 m (6,100 ft).During the summer, significant amounts of glacial rock flour flow into the lake from a nearby glacier, and these suspended rock particles are what give the lake a unique bright, turquoise colour. Because of its bright colour, photos of the lake often appear in illustrated books, and the area around the lake is a popular sightseeing spot for tourists. The lake is best seen from Bow Summit, the highest point on the Icefields Parkway.

The lake is fed by Peyto Creek, which drains water from Caldron Lake and Peyto Glacier (part of the Wapta Icefield). Peyto Lake is the origin of the Mistaya River, which heads northwest from the lake's outflow.


Rock dust, also known as rock powders, rock minerals, rock flour, soil remineralization, and mineral fines, consists of finely crushed rock, processed by natural or mechanical means, containing minerals and trace elements widely used in organic farming practices.

The igneous rocks basalt and granite often contain the highest mineral content, whereas limestone, considered inferior in this consideration, is often deficient in the majority of essential macro-compounds, trace elements, and micronutrients.

Rock dust is not a fertilizer, for it lacks the qualifying levels of nitrogen, potassium, and phosphorus.

Rockdust is also the limestone-based product sprayed on walls inside underground coal mines to keep coal dust levels down. This is to prevent coal dust explosions and also to prevent the incidence of black lung disease.

Thunder Creek (Washington)

Thunder Creek is a stream located entirely within North Cascades National Park and the Ross Lake National Recreation Area in the US state of Washington. Thunder Creek runs in a northerly direction most of its route starting from just north of Park Creek Pass in the south district of North Cascades National Park and ending at Diablo Lake in Ross Lake National Recreation Area. Prior to the construction of the Diablo Dam, Thunder Creek emptied into the Skagit River. A popular hiking trail parallels Thunder Creek its entire length. Thunder Creek is well known for having a turquoise appearance from the suspended silt and rock flour caused by runoff from dozens of glaciers, including the largest glacier in the park, Boston Glacier, which feeds Skagit Creek, a tributary stream.



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