Stack (geology)

A stack or seastack is a geological landform consisting of a steep and often vertical column or columns of rock in the sea near a coast, formed by wave erosion. Stacks are formed over time by wind and water, processes of coastal geomorphology. They are formed when part of a headland is eroded by hydraulic action, which is the force of the sea or water crashing against the rock. The force of the water weakens cracks in the headland, causing them to later collapse, forming free-standing stacks and even a small island. Without the constant presence of water, stacks also form when a natural arch collapses under gravity, due to sub-aerial processes like wind erosion. Stacks can provide important nesting locations for seabirds, and many are popular for rock climbing.

Isolated steep-sided, rocky oceanic islets, typically of volcanic origin, are also loosely called "stacks" or "volcanic stacks".

Formation

Stacks typically form in horizontally-bedded sedimentary or volcanic rocks, particularly on limestone cliffs. These rock types' medium hardness means medium resistance to abrasive and attritive erosion. A more resistant layer may form a capstone. (Cliffs with weaker rock—such as clay—tend to slump and erode too quickly to form stacks, while harder rocks such as granite erode in different ways.)

Stack

Stack may refer to:

Mathematics

Computers

People

Stack (unit)

Stack was a US unit of volume for stacked firewood. Symbol for the unit was stk.

Definition

108 cubic foot.

Conversion

1 stack ≡ 54/21 Load (squared)

1 stack≡ 108 cubic foot

1 stack≡ 3.058219431936 m³

References

Chimney

A chimney is a structure which provides ventilation for hot flue gases or smoke from a boiler, stove, furnace or fireplace to the outside atmosphere. Chimneys are typically vertical, or as near as possible to vertical, to ensure that the gases flow smoothly, drawing air into the combustion in what is known as the stack, or chimney, effect. The space inside a chimney is called a flue. Chimneys may be found in buildings, steam locomotives and ships. In the United States, the term smokestack (colloquially, stack) is also used when referring to locomotive chimneys or ship chimneys, and the term funnel can also be used.

The height of a chimney influences its ability to transfer flue gases to the external environment via stack effect. Additionally, the dispersion of pollutants at higher altitudes can reduce their impact on the immediate surroundings. In the case of chemically aggressive output, a sufficiently tall chimney can allow for partial or complete self-neutralization of airborne chemicals before they reach ground level. The dispersion of pollutants over a greater area can reduce their concentrations and facilitate compliance with regulatory limits.

Seah (unit)

The se'ah or seah (Hebrew: סאה‎) is a unit of dry measure of ancient origin used in Halakha (Jewish law), which equals one third of an ephah, or bath. Its size in modern units varies widely according to the criteria used for defining it.

According to Herbert G. May, chief editor of two classic Bible-related reference books, the bath may be archaeologically determined to have been about 5.75 gallons (22 liters) from a study of jar remains marked 'bath' and 'royal bath' from Tell Beit Mirsim. Since the bath unit has been established to be 22 litres, 1 se'ah would equal 7.33 litres or 7.33dm³.

In the context of a mikveh, a se'ah can be about twice as much in order to accommodate even the most stringent rabbinical ruling on immersion. A mikveh must, according to the classical regulations, contain enough water to cover the entire body of an average-sized person; based on a mikveh with the dimensions of 3 cubits deep, 1 cubit wide, and 1 cubit long, the necessary volume of water was estimated as being 40 se'ah of water. The exact volume referred to by a seah is debated, and classical rabbinical literature specifies only that it is enough to fit 144 eggs; most Orthodox Jews use the stringent ruling of the Avrohom Yeshaya Karelitz, according to which one seah is 14.3 litres, and therefore a mikveh must contain approximately 575 litres . This volume of water could be topped up with water from any source, but if there were less than 40 seahs of water in the mikveh, then the addition of 3 or more pints of water from an unnatural source would render the mikveh unfit for use, regardless of whether water from a natural source was then added to make up 40 seahs from a natural source; a mikveh rendered unfit for use in this way would need to be completely drained away and refilled from scratch.

90.9 Sea FM

90.9 Sea FM (callsign 4SEA) is a radio station on the Gold Coast, Queensland, Australia. It is part of the Southern Cross Austereo Today Network, and is also the network hub for the regional Today Stream, broadcasting shows at times from 9am - 12am across the Sea, Star and Hot FM Networks across Australia.

The Sea FM brand name and original logo was created by Gold Coast Broadcasters Pty Ltd for just the one station - 90.9 Sea FM - after the Gold Coast was granted a new commercial FM licence. 90.9 Sea FM began broadcasting in 1989 with programming consulted by Austereo. The original Sea FM on-air line-up was a strong team of experienced Announcers, many having made their name previously in Metropolitan radio including - Craig Bruce (FOX FM) & Sammy Power, Ian 'Lofty' Fulton (4IP), Grahame "Durry" Rodgers (2SM & 2NX), Sue Moses (2MMM & Channel 10), Gregg Easton (2UW & 4BK), Joe Miller (3XY & EON FM), Dean Miller and Simon Franks.

In November 2011, controversy erupted after rumours surfaced that popular long-term breakfast co-host, Moyra Major, was to be replaced by entertainer Charli Robinson, after Robinson had filled in for six weeks while Major was on maternity leave. It was reported that Major had been replaced due to a significant increase in ratings for the breakfast show during Robinson's stint as co-host.

Collins-class submarine replacement project

Identified as the most expensive defence procurement project to date in Australian history, the Collins-class replacement will provide Australia with a submarine capability deep into the twenty-first century. With the Royal Australian Navy's (RAN's) Collins-class submarines scheduled to begin leaving service from 2025 onwards, plans to replace them began in 2007 with the commencement of the defence acquisition project SEA 1000, also referred to as the Future Submarine Programme. Australia's unique operating environment (including significant variations in ocean climate and conditions) and rejection of nuclear propulsion had previously driven it to operate in the Collins-class the world's largest diesel-electric submarines, capable of transiting the long distances from HMAS Stirling to their deployment areas.

In the early phases of the replacement project, four design options were identified: purchase a Military-Off-The-Shelf (MOTS) design, modify a MOTS design for Australian conditions, design an evolution of the Collins-class, or create a new design. Nuclear propulsion has been ruled out due to the lack of an indigenous nuclear industry in Australia and public opposition to nuclear technology.