Rock flour, or glacial flour, consists of fine-grained, silt-sized

Silt

Silt is granular material of a size somewhere between sand and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil or as suspended sediment in a surface water body...

 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 river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 water making the water appear cloudy, which is sometimes known as glacial milk.

When the sediments enter a river, it turns the river's color gray, light brown, iridescent blue-green, or milky white. If the river flows into a glacial lake

Glacial lake

A glacial lake is a lake with origins in a melted glacier. Near the end of the last glacial period, roughly 10,000 years ago, glaciers began to retreat. A retreating glacier often left behind large deposits of ice in hollows between drumlins or hills. As the ice age ended, these melted to create...

, the lake

Lake

A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

 may appear turquoise

Turquoise (color)

Turquoise or is a slightly blueish tone of light green. The color is based on the gem turquoise. The term comes from the French for Turkish.At right is displayed the X11 color named turquoise....

 in color

Color

Color or colour is the visual perceptual property corresponding in humans to the categories called red, green, blue and others. Color derives from the spectrum of light interacting in the eye with the spectral sensitivities of the light receptors...

 as a result. When flows of the flour are extensive, a distinct layer of a different color 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 Louise

Lake Louise (Alberta)

Lake Louise is a lake in Alberta, Canada. The glacial lake is located in Banff National Park, from the hamlet of Lake Louise and the Trans-Canada Highway....

 and Peyto Lake

Peyto Lake

Peyto Lake is a glacier-fed lake located in Banff National Park in the Canadian Rockies. The lake itself is easily accessed from the Icefields Parkway...

 in Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 and Gjende

Gjende

Gjende 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—in length 18 km and in breadth 1.5 km at the broadest point with steep walls...

 lake in Norway

Norway

Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

.

Formation

Typically, natural rock flour is formed during glacial migration

Glacial motion

Glacial motion is the motion of glaciers, which can be likened to rivers of ice. It has played an important role in sculpting many landscapes. Most lakes in the world occupy basins scoured out by glaciers...

, where the glacier

Glacier

A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...

 grinds against the sides and bottom of the rock

Rock (geology)

In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...

 beneath it, but also is produced by freeze-and-thaw action, where the act of water freezing

Freezing

Freezing or solidification is a phase change in which a liquid turns into a solid when its temperature is lowered below its freezing point. The reverse process is melting....

 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

Clay minerals

Clay minerals are hydrous aluminium phyllosilicates, sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations. Clays have structures similar to the micas and therefore form flat hexagonal sheets. Clay minerals are common weathering products and low...

, but typically, ground up quartz

Quartz

Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...

 and feldspar

Feldspar

Feldspars are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's crust....

. Rock flour is carried out from the system via meltwater

Meltwater

Meltwater is the water released by the melting of snow or ice, including glacial ice and ice shelfs over oceans. Meltwater is often found in the ablation zone of glaciers, where the rate of snow cover is reducing...

 streams, where the particles travel in suspension

Suspension (chemistry)

In chemistry, a suspension is a heterogeneous fluid containing solid particles that are sufficiently large for sedimentation. Usually they must be larger than 1 micrometer. The internal phase is dispersed throughout the external phase through mechanical agitation, with the use of certain...

. Rock flour particles may travel great distances either suspended in water or carried by the wind

Wind

Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...

, in the latter case, forming deposits called loess

Loess

Loess is an aeolian sediment formed by the accumulation of wind-blown silt, typically in the 20–50 micrometre size range, twenty percent or less clay and the balance equal parts sand and silt that are loosely cemented by calcium carbonate...

.

Agricultural use

Some agronomists

Agricultural science

Agricultural science is a broad multidisciplinary field that encompasses the parts of exact, natural, economic and social sciences that are used in the practice and understanding of agriculture. -Agriculture and agricultural science:The two terms are often confused...

 believe that rock flour has a powerful effect in restoring trace minerals to soil

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

. An early experimenter was the German

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 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

John D. Hamaker

John D. Hamaker , was an American mechanical engineer, ecologist, agronomist and science writer in the fields of soil remineralization, rock dusting, mineral cycles, climate cycles and glaciology.-Biography:Background...

 argues 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

Alternative culture

Alternative culture is a type of culture that exists outside or on the fringes of mainstream or popular culture, usually under the domain of one or more subcultures...

 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

Granite

Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...

 and basalt

Basalt

Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...

ic fines by the U.S. Department of Agriculture exists at the Henry A. Wallace Beltsville Agricultural Research Center

Henry A. Wallace Beltsville Agricultural Research Center

The Henry A. Wallace Beltsville Agricultural Research Center, or BARC, is a unit of the United States Department of Agriculture's Agricultural Research Service. It is located at in Beltsville, Maryland, and is named for Henry A. Wallace, former United States vice president and secretary of...

. 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, environmentalist

Environmentalist

An environmentalist broadly supports the goals of the environmental movement, "a political and ethical movement that seeks to improve and protect the quality of the natural environment through changes to environmentally harmful human activities"...

s, and industry.

External links

• Remineralize the Earth - "non-profit organization incorporated to disseminate ideas and practice about soil remineralization".
• Earth Regeneration Society Official Site
• On a Fad Diet of Rock Dust, How the Garden Does Grow Henry Homeyer, June 24, 2004, New York Times.
• Soil remineralization: a future market for aggregate industry fines, Robert J. Able, June 1995, Pit & Quarry.
• Julius Hensel
• Julius Hensel by John Mann
• http://www.activecompost.com/Co-utilization%20of%20Rockdust,%20Mineral%20Fines%20and%20Compost.pdf Downloadable document on co-utilisation of mineral fines and composts
• Global Warming Triggers Ice Age Remineralization Connection in Living Nutrition magazine.
• http://pubs.usgs.gov/of/2004/1216/index2.html The USGS Glossary of Glacial Terminology