Glacial flour
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Rock flour, or glacial flour, consists of fine-grained,
silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension with water. Silt usually has a floury feel when ...
-sized particles of rock, generated by mechanical grinding of bedrock by
glacial erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...
or by artificial grinding to a similar size. Because the material is very small, it becomes suspended in
meltwater Meltwater is water released by the melting of snow or ice, including glacial ice, tabular icebergs and ice shelves over oceans. Meltwater is often found in the ablation zone of glaciers, where the rate of snow cover is reducing. Meltwater can be ...
making the water appear cloudy, which is sometimes known as glacial milk. 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 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. Formation Near the end of the last glacial period, roughly 10,0 ...
, the lake may appear
turquoise Turquoise is an opaque, blue-to-green mineral that is a hydrated phosphate of copper and aluminium, with the chemical formula . It is rare and valuable in finer grades and has been prized as a gemstone and ornamental stone for thousands of yea ...
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 Lake Pukaki is the largest of three roughly parallel alpine lakes running north–south along the northern edge of the Mackenzie Basin on New Zealand's South Island. The others are Lakes Tekapo and Ohau. All three lakes were formed when the te ...
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, and many lakes in the
Cascade Range The Cascade Range or Cascades is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, ...
of
Washington State Washington (), officially the State of Washington, is a state in the Pacific Northwest region of the Western United States. Named for George Washington—the first U.S. president—the state was formed from the western part of the Washington ...
(including Diablo Lake, Gorge Lake, and
Blanca Lake Blanca Lake is located in the Henry M. Jackson Wilderness Area in the Cascade Mountains of the U.S. state of Washington. Blanca Lake sits in a basin surrounded by the peaks of Monte Cristo, Kyes, and Columbia. The lake is fed by the Columbi ...
).


Formation

Typically, natural rock flour is formed during glacial migration, where the
glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its Ablation#Glaciology, ablation over many years, often Century, centuries. It acquires dis ...
grinds against the sides and bottom of the
rock Rock most often refers to: * Rock (geology), a naturally occurring solid aggregate of minerals or mineraloids * Rock music, a genre of popular music Rock or Rocks may also refer to: Places United Kingdom * Rock, Caerphilly, a location in Wales ...
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 Clay minerals are hydrous aluminium phyllosilicates (e.g. kaolin, Al2 Si2 O5( OH)4), sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations found on or near some planetary surfaces. Clay mineral ...
but typically ground up
quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...
and
feldspar Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) feldsp ...
. Rock flour is carried out from the system via
meltwater Meltwater is water released by the melting of snow or ice, including glacial ice, tabular icebergs and ice shelves over oceans. Meltwater is often found in the ablation zone of glaciers, where the rate of snow cover is reducing. Meltwater can be ...
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 Loess (, ; from german: Löss ) is a clastic, predominantly silt-sized sediment that is formed by the accumulation of wind-blown dust. Ten percent of Earth's land area is covered by loess or similar deposits. Loess is a periglacial or aeolian ...
.


Agricultural use

Rock flour, artificial or natural, is a source of
plant micronutrients Plant nutrition is the study of the chemical elements and compounds necessary for plant growth and reproduction, plant metabolism and their external supply. In its absence the plant is unable to complete a normal life cycle, or that the element i ...
(
minerals In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...
trace elements) widely used in organic farming practices. Synonyms in this case include rock dust, rock powders, rock minerals, and mineral fines. The
igneous rock Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main The three types of rocks, rock types, the others being Sedimentary rock, sedimentary and metamorphic rock, metamorphic. Igneous rock ...
s
basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...
and
granite Granite () is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies undergro ...
often contain the highest mineral content, whereas
limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
, considered inferior in this consideration, is often deficient in the majority of essential macro-compounds, trace elements, and
micronutrient Micronutrients are nutrient, essential dietary elements required by organisms in varying quantities throughout life to orchestrate a range of physiological functions to maintain health. Micronutrient requirements differ between organisms; for exam ...
s.


Background

Soil remineralization (in the sense of re-incorporating minerals, different from
remineralisation In biogeochemistry, remineralisation (or remineralization) refers to the breakdown or transformation of organic matter (those molecules derived from a biological source) into its simplest inorganic forms. These transformations form a crucial link ...
in biogeochemistry) creates fertile
soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...
s by returning minerals to the soil which have been lost by erosion, leaching, and or over-farming. It functions the same way that the Earth does: during an Ice Age, glaciers crush rock onto the Earth's soil mantle, and winds blow the dust in the form of
loess Loess (, ; from german: Löss ) is a clastic, predominantly silt-sized sediment that is formed by the accumulation of wind-blown dust. Ten percent of Earth's land area is covered by loess or similar deposits. Loess is a periglacial or aeolian ...
all over the globe. Volcanoes erupt, spewing forth minerals from deep within the Earth, and rushing rivers form mineral-rich alluvial deposits. Rock dust is added to soil to improve
fertility Fertility is the capability to produce offspring through reproduction following the onset of sexual maturity. The fertility rate is the average number of children born by a female during her lifetime and is quantified demographically. Fertili ...
and has been tested since 1993 at the Sustainable Ecological Earth Regeneration Centre (SEER Centre) in Straloch, near Pitlochry, in
Perth and Kinross Perth and Kinross ( sco, Pairth an Kinross; gd, Peairt agus Ceann Rois) is one of the 32 council areas of Scotland and a Lieutenancy Area. It borders onto the Aberdeenshire, Angus, Argyll and Bute, Clackmannanshire, Dundee, Fife, Highland and S ...
,
Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the ...
. Further testing has been undertaken by James Cook University, Townsville, Far North
Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...
.


History

Thomas J. Goreau Thomas J. Goreau (Tom Goreau, * 1950 in Jamaica) is a biogeochemist and marine biologist. He is the son of two other renowned marine biologists, Thomas F. Goreau and Nora I. Goreau. After studying in Jamaican primary and secondary schools, he re ...
who wrote the book ''Geotherapy'' believe that mafic/ultra-mafic rock flour has a powerful effect in restoring trace minerals to soils, which increases the health and vigour of the Microorganism, Plantae, Animalia pathway and also sequesters carbon. 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 John D. Hamaker (1914–1994), was an American mechanical engineer, ecologist, agronomist and science writer in the fields of soil regeneration, rock dusting, mineral cycles, climate cycles and glaciology. Biography Background Hamaker was born ...
argued that widespread remineralization of soils with
rock dust Rock most often refers to: * Rock (geology), a naturally occurring solid aggregate of minerals or mineraloids * Rock music, a genre of popular music Rock or Rocks may also refer to: Places United Kingdom * Rock, Caerphilly, a location in Wales ...
will be necessary to reverse soil depletion by current agriculture and forestry practice. While this originally was an
alternative Alternative or alternate may refer to: Arts, entertainment and media * Alternative (''Kamen Rider''), a character in the Japanese TV series ''Kamen Rider Ryuki'' * ''The Alternative'' (film), a 1978 Australian television film * ''The Alternative ...
concept, increasing mainstream research has been devoted to
soil amendment A soil conditioner is a product which is added to soil to improve the soil’s physical qualities, usually its fertility (ability to provide nutrition for plants) and sometimes its mechanics. In general usage, the term "soil conditioner" is often ...
and other benefits of rock flour application: for instance, a pilot project on the use of glacial rock,
granite Granite () is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies undergro ...
and
basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...
ic fines by the U.S. Department of Agriculture exists at the
Henry A. Wallace Beltsville Agricultural Research Center The Henry A. Wallace Beltsville Agricultural Research Center (BARC), also known as the National Agricultural Research Center, is a unit of the United States Department of Agriculture's Agricultural Research Service. It is located in unincorporate ...
. 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 An environmentalist is a person who is concerned with and/or advocates for the protection of the environment. An environmentalist can be considered a supporter of the goals of the environmental movement, "a political and ethical movement that se ...
s, and industry.


Research

SEER's research claims that the benefits of adding rockdust to soil include increased moisture-holding properties in the soil, improved
cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
exchange capacity and better soil structure and drainage. Rockdust also provides
calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...
,
iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
,
magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
,
phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...
and
potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosphe ...
, plus trace elements and
micronutrient Micronutrients are nutrient, essential dietary elements required by organisms in varying quantities throughout life to orchestrate a range of physiological functions to maintain health. Micronutrient requirements differ between organisms; for exam ...
s. By replacing these
leach Leach may refer to: * Leach (surname) * Leach, Oklahoma, an unincorporated community, United States * Leach, Tennessee, an unincorporated community, United States * Leach Highway, Western Australia * Leach orchid * Leach phenotype, a mutation in ...
ed minerals it is claimed that soil health is increased and that this produces healthier plants.


Composition

Silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic tab ...
is thought to be the major element effecting the strength of cell wall development. However it is the amount of available silica that has a dramatic effect on the plant strength and subsequent health. To highlight this, plants that are grown in very sandy soils, (being high in non available silica), often require a silica based fertiliser to provide available silicon. Silicon comes in silicon multi-oxide molecules (e.g. SiO2, SiO4, SiO6, and SiO8). Each molecule shape is thought to pack in different ways to allow different levels of availability. Often phosphorus is locked in soils due to many years of application of traditional fertilisers. The use of micronutrient-rich fertiliser enables plants to access locked phosphorus. The elements high in available 2+ valence electrons, calcium, iron and magnesium in particular contribute to
paramagnetism Paramagnetism is a form of magnetism whereby some materials are weakly attracted by an externally applied magnetic field, and form internal, induced magnetic fields in the direction of the applied magnetic field. In contrast with this behavior, ...
in soil which aid in
cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
exchange capacity. The
calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...
and
magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
in high quality have the ability to neutralise pH in soils, in effect acting as a liming agent.


Application

Rock dust can be applied to soil by hand application, via
broadcast spreader A broadcast seeder, alternately called a broadcaster, broadcast spreader or centrifugal fertilizer spreader (Europe) or "spinner" (UK), is a farm implement commonly used for spreading seed where no row planting is required (mostly for lawns and me ...
or by
fertigation Fertigation is the injection of fertilizers, used for soil amendments, water amendments and other water-soluble products into an irrigation system. Fertigation is related to chemigation, the injection of chemicals into an irrigation system. The ...
. Where possible the rockdust can be worked into the ground either physically or by using water to wash in. In some soils which display poor levels of nutrients, application rates of 10 tonnes per hectare are required. In
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
, namely the Riverland, Riverina, Langhorne Creek, Barossa and
McLaren Vale McLaren Vale is a wine region in the Australian state of South Australia located in the Adelaide metropolitan area and centred on the town of McLaren Vale about south of the Adelaide city centre. It is internationally renowned for the wine ...
regions, rates are 3–5 tonnes per
hectare The hectare (; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100-metre sides (1 hm2), or 10,000 m2, and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is a ...
. In a garden application, this might equate to 400 grams per square metre.


See also

*
Diatomaceous earth Diatomaceous earth (), diatomite (), or kieselgur/kieselguhr is a naturally occurring, soft, siliceous sedimentary rock that can be crumbled into a fine white to off-white powder. It has a particle size ranging from more than 3  μm to le ...
* Greensand, used as a source of potassium * Organic farming *
Organic fertilizer Organic fertilizers are fertilizers that are naturally produced. Fertilizers are materials that can be added to soil or plants, in order to provide nutrients and sustain growth. Typical organic fertilizers include all animal waste including mea ...
*
Phosphorite Phosphorite, phosphate rock or rock phosphate is a non-detrital sedimentary rock that contains high amounts of phosphate minerals. The phosphate content of phosphorite (or grade of phosphate rock) varies greatly, from 4% to 20% phosphorus pentoxi ...
, also called rock phosphate *
Soil conditioner A soil conditioner is a product which is added to soil to improve the soil’s physical qualities, usually its fertility (ability to provide nutrition for plants) and sometimes its mechanics. In general usage, the term "soil conditioner" is often ...


References


External links


Remineralize the Earth
– "non-profit organization incorporated to disseminate ideas and practice about soil remineralization"

The USGS Glossary of Glacial Terminology {{DEFAULTSORT:Rock Flour Glaciology Soil Agronomy Organic fertilizers Soil improvers