Volcanic ash

Volcanic ash consists of fragments of pulverized rock, minerals and volcanic glass, created during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to refer to all explosive eruption products (correctly referred to as tephra), including particles larger than 2mm. Volcanic ash is formed during explosive volcanic eruptions when dissolved gases in magma expand and escape violently into the atmosphere. The force of the escaping gas shatters the magma and propels it into the atmosphere where it solidifies into fragments of volcanic rock and glass. Ash is also produced when magma comes into contact with water during phreatomagmatic eruptions, causing the water to explosively flash to steam leading to shattering of magma. Once in the air, ash is transported by wind up to thousands of kilometers away.

Due to its wide dispersal, ash can have a number of impacts on society, including human and animal health, disruption to aviation, disruption to critical infrastructure (e.g., electric power supply systems, telecommunications, water and waste-water networks, transportation), primary industries (e.g., agriculture), buildings and structures.

Ash

Ash or ashes are the solid remains of fires. Specifically, it refers to all non-aqueous, non-gaseous residues that remains after something is burned. In analytical chemistry, in order to analyse the mineral and metal content of chemical samples, ash is the non-gaseous, non-liquid residue after a complete 100% combustion.

Ashes as the end product of incomplete combustion will be mostly mineral, but usually still contain an amount of combustible organic or other oxidizable residues. The most well-known type of ash is wood ash, as a product of wood combustion in campfires, fireplaces, etc.. The darker the wood ashes, the higher the content of remaining charcoal will be due to incomplete combustion.

Like soap, ash is also a disinfecting agent (alkaline). WHO recommended ash or sand as alternative to soap when soap is not available.

Other specific types

Ash (near Salway)

Coordinates: 50°46′N 2°46′W / 50.76°N 02.76°W / 50.76; -02.76

Ash is a hamlet approximately 0.6 miles (1 km) east of the village of Salway, Dorset, England.

References

Almquist shell

The Almquist shell (also known as A Shell, ash and sh) is a lightweight Unix shell originally written by Kenneth Almquist in the late 1980s. Initially a clone of the System V.4 variant of the Bourne shell, it replaced the original Bourne shell in the BSD versions of Unix released in the early 1990s. Derivative versions of ash are still installed as the default shell (/bin/sh) on FreeBSD, NetBSD, DragonFly BSD, MINIX, and Android, and in some Linux distributions.

Debian and derived Linux distributions such as Ubuntu ship a version of ash, known as dash (Debian Almquist shell), as the default /bin/sh, although Bash is the default login shell for interactive use. The reason for using dash is faster shell script execution, especially during startup of the operating system, compared to previous versions of Debian and Ubuntu that used Bash for this purpose.

Ash is also fairly popular in embedded Linux systems; its code was incorporated into the BusyBox catch-all executable often employed in this area.