Alluvium

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Alluvium

Alluvium (from the Latin

Latin

Latin is an Italic language, historically spoken in Latium and Ancient Rome. Through the Military history of the Roman Empire, Latin spread throughout the Mediterranean and a large part of Europe....
, alluvius, from alluere, "to wash against") is soil

Soil

Soil is the naturally occurring, unconsolidated or loose covering on the Earth's surface. Soil is composed of particles of broken rock that have been altered by chemical and environmental processes including weathering and erosion....
or sediment

Sediment

Sediment is any particulate matter that can be sediment transport by fluid dynamics, and which eventually is deposited.Sediments are most often transported by water transported by wind and glaciers....
s deposited by a river or other running water. Alluvium is typically made up of a variety of materials, including fine particles of silt

Silt

Silt is soil or Rock derived granular material of a Particle size between sand and clay. Silt may occur as a soil or as suspended sediment in a surface water body....
and clay

Clay

Clay is a naturally occurring material composed primarily of fine-grained minerals, which show plasticity through a variable range of water content, and which can be hardened when dried and/or fired....
and larger particles of sand

Sand

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.As the term is used by geologists, sand particles range in diameter from 0.0625 to 2 millimeters....
and gravel

Gravel

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Alluvium (from the Latin

Latin

Soil

Sediment

Silt

Silt is soil or Rock derived granular material of a Particle size between sand and clay. Silt may occur as a soil or as suspended sediment in a surface water body....
and clay

Clay

Sand

Gravel

Gravel is rock that is of a specific particle size range. Specifically, it is is any loose rock that is larger than two millimeters in its largest dimension and no more than 64 millimeters ....
.

Flowing water associated with glaciers may also deposit alluvium, but deposits directly from ice are not alluvium (see glacial till).

A river is continually picking up and dropping solid particles of rock and soil from its bed throughout its length. Where the river flow is fast, more particles are picked up than dropped. Where the river flow is slow, more particles are dropped than picked up. Areas where more particles are dropped are called alluvial or flood plains, and the dropped particles are called alluvium.

Even small streams make alluvial deposits, but it is in the flood plains and delta

River delta

A delta is a landform that is created at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river....
s of large rivers that large, geologically-significant alluvial deposits are found.

The amount of matter carried by a large river is enormous. The names of many rivers derive from the color that the transported matter gives the water. For example, the Huang He in China is literally translated "Yellow River", and the Mississippi River

Mississippi River

The Mississippi River is the longest river in the United States, with a length of from its source in Lake Itasca in Minnesota to its mouth in the Gulf of Mexico....
in the United States is also called Big Muddy. It has been estimated that the Mississippi River

Mississippi River

The Mississippi River is the longest river in the United States, with a length of from its source in Lake Itasca in Minnesota to its mouth in the Gulf of Mexico....
annually carries 406 million tons of sediment to the sea, the Huang He 796 million tons, and the Po River

Po River

The Po is a river that flows 652 km eastward across northern Italy, from Monviso to the Adriatic Sea near Venice. It has a drainage area of 71,000 km? and is the longest river in Italy....
in Italy 67 million tons.

Alluvium often contains valuable ores such as gold

Gold

Gold is a chemical element with the symbol Au and atomic number 79. It is a highly sought-after precious metal, having been used as money, as a store of value, in jewelry, in sculpture, and for ornamentation since the beginning of recorded history....
and platinum

Platinum

Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is in Group 10 of the periodic table of elements....
and a wide variety of gemstone

Gemstone

A gemstone or gem, also called a precious or semi-precious stone, is a piece of attractive mineral, which — when cut and polished — is used to make jewellery or other adornments....
s. Such concentrations of valuable ore

Ore

An ore is a type of Rock that contains minerals such as gemstones and metals that can be extracted through mining and refined for use. Samples of ore in the form of exceptionally beautiful crystals, exotic layering visible when sectioned or polished or metallic presentations such as large nuggets or crystalline formations of metals suc...
s is termed a placer deposit

Placer deposit

In geology, a placer deposit or placer is an accumulation of valuable minerals formed by deposition of dense mineral phases in a trap site....
.

Throughout history, many shallow lakes have been filled in with alluvium to leave fertile

Fertile

Fertile is the ability organisms, including people or animals, to produce healthy offspring.Fertile may also refer to:*Fertile material, nuclides which generally themselves do not undergo induced fission, but from which fissile material can be generated...
plains (alluvial soils are often very fertile). The alluvial mud annually deposited by the Nile

Nile

The Nile is a major north-flowing river in Africa, generally regarded as the List of rivers by length in the world.The Nile has two major tributary, the White Nile and Blue Nile, the latter being the source of most of the Nile's water and silt, but the former being the longer of the two....
has enabled the Egyptians

Ancient Egypt

Ancient Egypt was an Ancient history civilization in eastern North Africa, concentrated along the lower reaches of the Nile in what is now the modern nation of Egypt....
to grow crops since at least the 4th millennium BC without artificial fertilization.

Since the construction of the Aswan Dam

Aswan Dam

Aswan is a city on the first Cataracts of the Nile of the Nile in Egypt.Two dams straddle the river at this point: the newer Aswan High Dam , and the older Aswan Dam or Aswan Low Dam....
on The Nile in Egypt

Egypt

Egypt is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Western Asia. Covering an area of about , Egypt borders the Mediterranean Sea to the north, the Gaza Strip and Israel to the northeast, the Red Sea to the east, Sudan to the south and Libya to the west....
, 95% of the alluvium deposits at the mouth of the Nubia-Nasser Lake are gone, thus depriving the Nile delta

Nile Delta

The Nile Delta is the River delta formed in Northern Egypt where the Nile River spreads out and drains into the Mediterranean Sea. It is one of the world's largest river deltas?from Alexandria in the west to Port Said in the east, it covers some 240 km of Mediterranean coastline?and is a rich agricultural region....
of its fertility. Since 1964, 3.8 billion cubic meters of sediments have deposited in this man-made lake. Proposals have been made to dredge this alluvium and pump it in slurry pipeline

Slurry pipeline

A slurry pipeline is used in mining to transport mineral concentrate from a mineral processing plant near a mine....
s to shore where it can be used to fertilize the desert.

Footnotes

Notations

"Dennis Garrett", http://www.alaskafreegold.com Blue Ribbon Mine, Alaska

Alluvium

Footnotes

Notations

See also