What is Adsense?

AdSense is an ad serving application run by Google Inc. Website owners can enroll in this program to enable text, image, and video advertisements on their websites. These advertisements are administered by Google and generate revenue on either a per-click or per-impression basis. Google beta tested a cost-per-action service, but discontinued it in October 2008 in favor of a DoubleClick offering (also owned by Google). In Q1 2010, Google earned US$2.04 billion ($8.16 billion annualized), or 30% of total revenue, through AdSense.

Google uses its Internet search technology to serve advertisements based on website content, the user's geographical location, and other factors. Those wanting to advertise with Google's targeted advertisement system may enroll through AdWords. AdSense has become a popular method of placing advertising on a website because the advertisements are less intrusive than most banners, and the content of the advertisements is often relevant to the website.

Many websites use AdSense to monetize their content; it is the most popular advertising network. AdSense has been particularly important for delivering advertising revenue to small websites that do not have the resources for developing advertising sales programs and sales people. To fill a website with advertisements that are relevant to the topics discussed, webmasters implement a brief script on the websites' pages. Websites that are content-rich have been very successful with this advertising program, as noted in a number of publisher case studies on the AdSense website.

Some webmasters invest significant effort into maximizing their own AdSense income. They do this in three ways:

1. They use a wide range of traffic-generating techniques, including but not limited to online advertising.
2. They build valuable content on their websites that attracts AdSense advertisements, which pay out the most when they are clicked.
3. They use text content on their websites that encourages visitors to click on advertisements. Note that Google prohibits webmasters from using phrases like "Click on my AdSense ads" to increase click rates. The phrases accepted are "Sponsored Links" and "Advertisements".

The source of all AdSense income is the AdWords program, which in turn has a complex pricing model based on a Vickrey second price auction. AdSense commands an advertiser to submit a sealed bid (i.e., a bid not observable by competitors). Additionally, for any given click received, advertisers only pay one bid increment above the second-highest bid. Google currently shares 68% of revenues generated by AdSense with content network partners. 

I'll post tips and tricks using adsense soon...

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Justin Bieber: Never Say Never

JUSTIN BIEBER: NEVER SAY NEVER (2011)

Quality: DVDRip

Release Date: 11 February 2011

Info: imdb.com/title/tt1702443/

Trailer: imdb.com/video/imdb/vi1280219417/

Starring: Justin Bieber, Boys II Men and Miley Cyrus

Uploader by rezaldi, vermouth

SINOPSIS

Follows Justin Bieber with some footage of performances from his 2010 concert tour.

DOWNLOAD

Part 1 | Part 2 [mkv-400MB]|bu

Pass: indofiles.org

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Single Link [avi-700MB]|bu

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Single Link [avi-700MB]|jc
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Military Notebook

Intel security and state security is something that should be kept in strict confidentiality of the criminals. Espionage and sabotage is a threat to a country. There's a new sophistication, may I also just found out about a special notebook for the Military, i do not know is where the country's military-owned notebook, which is certainly the most advanced notebook owned by the military that his country forward.

Special Features & Technology Sophistication
* Customization or expansion space for greater flexibility * Certified to MIL-STD 810F & IP54 * Certificate of MIL-STD 461E for EMI * Rain, dust, vibration, and shock resistant design * Built - 20 on heating to operating temperature C * 1 GB Built-in Mini PCI LAN card * Sealed ports and connector covers * Wireless capabilities* Standard DVI Output DVI Output Standards * Military connectors* Magnesium casing (Military Green)

CPU: Intel Core 2 Duo processor with 4MB L2 cache Memory: 1GB, up to 4GB of 667MHz DDR2 DRAM Storage: Removable 2.5 "SATA Shock-mounted 160GB HDD Standard (upgradeable) DVD-ROM standard interchangeable exchanged with other components Display: LCD 15.1 "XGA (1024 x 768) Anti-Reflective Sunlight Readable TFT LCD 15.1" SXGA (optional) Video Controller: Integrated 32-bit 3D/2D gfx core with 224MB shared RAM Integrated 32-bit 3D/2D GFX core with 224MB shared RAM Audio: Audio: Built-in AC97 16-bit stereo sound card and speakers Standard Keyboard 87-key standard, non-backlit Operating System: Windows Vista ® Business (2GB memory upgrade is recommended for the Vista ® XP downgrade. The options available) Casing: Magnesium Magnesium (Military Green)

 

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Raining Blobs Mystery

In 1994, a strange phenomenon is happening in Oakville, Washington, USA. Areas with a population of about 665 people are surprised by a strange phenomenon that occurred in their areas. Rain fell in heavy, but not the usual rain, but rain mysterious substance in the form gels. The strangeness does not end there, after the mysterious rain subsided, some residents began to experience flu symptoms. What is the mysterious rain cause?
These events occurred exactly on the date of August 7, 1994 in the morning. Residents did not realize that on that day will happen rain. Then, not long after, the rain was falling, but rain is not rain water but a mysterious substance in the form of gels. 

  

Mysterious rain that did not last long. After subsided, residents saw lumps gels were scattered where - where. Because the event was unprecedented in Oakville, so many people who tried to hold the substance in the form of gels. A local policeman said, "The substance is very soft, like holding a lump of jelly in your hands. We know that many strange phenomena in this world, but it's true - really something unusual."

 

 

By late afternoon, most people begin to experience strange symptoms on their bodies. They experienced dizziness - dizziness, nausea, difficulty breathing, and even some residents who until unconscious. Dozens or perhaps hundreds of residents rushed to local hospitals, and that makes surprise is a symptom suffered by every - every resident is different. There are only experiencing flu symptoms, there is suffering from serious vertigo with complications in the eyes, there is also suffering from inner ear infections. Since many who suspect that a mysterious plague epidemic was caused by rain odd, then one resident named Sunny brought the strange substance to the hospital for examination.

After investigation by the hospital, a lab technician to announce the results of lab tests. According to him the substance of human white blood cells megansung, hmm .. similar to the red rain in Kerala, but with different cases. We are not sure whether this is the cause of the epidemic in this region, but we have sent samples to the Washington Health Department for further investigation.
Meanwhile, one other microbiological named Mike McDowell said that if he did not find any biological structure in the substance of it, but he found two types of bacteria that is harmful to humans. One of them attacked the human digestive system, but Mike also can not ensure the kind of bacteria.
Then, from which this substance come from? some people suspect that the mysterious substance derived from human waste being dumped from an airplane komersil.Tetapi, the theory because it got a rebuttal in accordance with FAA regulations, the dirt is removed from commercial aircraft is blue because it is mixed with a special material, while the substance is actually clear.
According to one resident, the rain had flushed the peculiar Oakville 6 times in 3 weeks. Many people are sick and too many animals that die after holding a strange lump it. Residents were then brought samples of these lumps and took it to another microbiological experts, namely Tim Davis.
After investigation, Davis said that he found in a eukaryotic cell clumps, although he has not fully convinced. He said that the eukaryotic cells are cells found in living organisms, especially in animals.
Because cases of this strange lump rain is still a mystery and yet unsolved, comes the speculation about the events that struck the Oakville on August 7, 1994. One of the most popular theory is the chemtrail theory. A resident said that many low-flying military aircraft in their area, sometimes even no black helicopters flying too low through the Oakville area. They suspect that the mysterious substance tersbeut derived from these planes and helicopters.
Unfortunately, their theory until now still has not been proven, although it sounded convincing. However, rain terjadu mysterious substance in Oakville region still holds a mystery until today, and the biggest question that haunts the population of Oakville is Where, how, and why the strange events that hit their area.

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Japan Nuclear Disaster 1/3

Japan's March 11 earthquake/tsunami-caused nuclear disaster affects millions of people regionally and throughout the Northern Hemisphere. But you'd never know it from most major media reports, downplaying an unfolding catastrophe.
In fact, distinguished experts like Helen Caldicott long ago warned of inevitable nuclear disasters, especially in seismically active areas. On May 23, 2004, The Japan Times contributor Leuren Moret headlined, "Japan's deadly game of nuclear roulette," saying:
"Of all the places in all the world no one in their right mind would build scores of nuclear power plants, Japan would be pretty near the top of the list."
"Japan sits on top of four tectonic plates....and is one of the most tectonically active regions of the world. (There) is almost no geologic setting in the world more dangerous for nuclear power than Japan."
In 2004, Kobe University Seismologist/Professor Katsuhiko Ishibashi called the situation then "very scary. It's like a kamikaze terrorist wrapped in bombs just waiting to explode."

 

American cities like New York have no credible evacuation plans in case of nuclear disasters. Neither does Japan, its Fukushima response a clear example. In fact, however, there's no adequate plan possible in cases of catastrophic nuclear events. How and to where do you transfer millions of people. Abandoning the technology alone can work, a possibility not considered, at least not so far.

Japanese nuclear engineer Yoichi Kikuchi told Moret about serious longstanding safety problems at Japanese nuclear facilities, including cooling system cracks in pipes from reactor vibrations. Operators are thus "gambling in a dangerous game to increase profits and decrease government oversight," he said.
Former GE senior field engineer Kei Sugaoka agreed, saying:
"The scariest thing, on top of all the other problems, is that all the nuclear power plants are aging, causing a deterioration of piping and joints which are always exposed to strong radiation and heat."
As a result, Moret, like Caldicott, said:
"It is not a question of whether or not a nuclear disaster will occur in Japan (or most anywhere); it is a question of when it will occur," and if catastrophic enough, perhaps nothing can be done to contain it.
Moreover, all radiation, especially large amounts, is harmful, cumulative, permanent and unforgiving. Yet lunatic fringe, self-styled "nuclear experts" like Ann Coulter told Fox News host Bill O'Reilly that a "growing body of evidence (shows radiation) is actually good for you and reduces cases of cancer." Even O'Reilly reacted skeptically to the "hormesis" notion. Wikipedia calls it:
"the term for generally-favorable biological responses to low exposures to toxins and other stressors," including radiation.
Other toxins aside, no amount of radiation is safe. In her book "Nuclear Madness," Helen Caldicott explained:
"Lower doses of radiation can cause abnormalities of the immune system and can also cause leukemia five to ten years after exposure; (other) cancer(s), twelve to sixty years later; and genetic diseases and congenital anomalies in future generations."

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8 things that can make you forgetful

Often forgotten and difficult to remember something? Could be, there is a problem that makes your brain recording system is disturbed.



If you have a habit of forgetting should not be underestimated. Find out what causes you easily forget the past eight the following signs:

1. High blood sugar levels
Storage memory can be disrupted due to high blood sugar. Beware, this condition can interfere with the brain associated with memory. If you have a family history of diabetes, you should control your sugar intake. Do also test blood sugar regularly.

And do not forget to keep a healthy diet and stay active. Walking is one effective alternative to prevent diabetes.

2. Less Rest
Brains rely on sleep activities to keep the new memory. In one study, respondents who sleep six hours a night for two weeks might not feel the lack of sleep. However, after the memory tests substantially, a result they are difficult given the short-term memory.

Sharpen your memory with a priority of adequate rest. If you can not, try doing a short sleep for six minutes while the body feels tired. This method can improve performance and lead to important memory processes in the brain.

3. Snore
Snoring can not only interfere with sleep quality, but also can reduce memory. Snoring during sleep, your airway will be blocked, so the cutting oxygen a few seconds at a time and causes the brain cells 'hunger'.

According to studies, men were more frequent snoring than women. And, other risk factors, this habit could arise due to being overweight or aged over 40 years.

Well, if you or your spouse have a habit of snoring, you should consult your doctor. You may need to wear special devices to cope with snoring during sleep for the flow of oxygen can pass into the brain. That way, your memory can be increased again.

4. Metabolism decreases
If this happens, chances are you have a thyroid problem. Thyroid hormones control the body's metabolism. If the production is too much or too little can disrupt brain cells, which can slow the entry of information into the brain. Solution: do not hurt you to see her doctor to solve this problem.

5. More than 65 years of age
At this age, humans will be more difficult to absorb vitamin B12 from food. Serious B12 deficiency can cause Alzheimer's disease or dementia. Therefore, seiringnya gets older, do consult with your doctor to find out how to increase your intake of B12, for example with the supplements. Besides the elderly, vegetarians adherents also often deficient in vitamin B12. \

6. Depressed
Patients with major depression also experienced a disruption in brain cells. In fact, when the depression lasts, there is the possibility of this condition can kill brain cells, causing memory 'degenerate'.

The solution, immediately seek treatment. The reason, more and more brain cells are 'missing', memory will become increasingly difficult to increase.

7. Eating allergy medication or sleeping pills
Drugs to cope with problems such as insomnia, allergies, and impaired planning, it also can cause impaired brain function. Thus, before taking this medication should consult your doctor for your memory does not go distracted.

8. Too much consumption of drugs
If the consume five or more drugs, you are a higher risk of memory disorders. Therefore, make sure your doctor knows all medications you consume. If a pharmacy ads look tempting, do not immediately tempted. We recommend minimizing the consumption of OTC drugs or only in accordance with the prescription drug consumption.

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The Longest Name of Place

DO NOT be surprised if you read the title of this paper. Just so you know, that's the name of a lake in the middle of the state of Massachusetts, USA.


Weird, right?It name is Chargoggagoggmanchauggagoggchaubunagungamaugg.How to read it? Let alone you, the locals gave up each time asked to pronounce a name that consists of 45 letters (if you do not believe please count yourself).


So, the simple locals call the lake with an easy name spelled: Lake Webster.



Because it is so complicated collection of letters to be read and written so often happened mistake and spelling, not least on the board of directions to the location of the lake.


For the mistake, thus proclaimed the Associated Press, Tuesday (21 / 4), local officials agreed to soon fix it, in line with the results of a combination of historical research about the strange spelling.


As the results of research Telegram & Gazette Worcester, the letter "o" in the letter to-20 should be "u" and "h" in the letter to the 38th should be "n". Well.


Just so you know, too, about the unique name that saves a lot of myths. One myth says that the long word that has meaning: "You're fishing at your side, I was fishing at my side, and no one is fishing in the middle."


The lake is the main fishing spots are located in the border area of residence several native tribes, and is the location of meetings of the various paths that a tribal transportation facilities around the lake. Based on these reasons, these funds are also often used as a meeting place. 


The tribes of Algonkin speakers have some name for this lake that can be recorded on old maps and historical records. However, all names diguanakan most have a similar meaning. Among the ancient name used for this lake there are names like "Chabanaguncamogue" and "Chaubanagogum".


A map of the town of Dudley in 1795 to write the name of this lake as Chargoggaggoggmanchoggagogg. Lake survey conducted in 1830 to write the name of this lake as Chaubunagungamaugg (old name). The following year, in Dudley and Oxford city maps that are neighbors, the lake was written as a Lake Chargoggagoggmanchauggagoggchaubunagungamaugg.

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The Origin Of HIV/AIDS

The debate over the origin of AIDS has been very interesting and disputed since the beginning of the epidemic. However, the danger of trying to identify where AIDS originated. People can use it as a matter of debate to blame a particular group or lifestyle. 

The first AIDS case was found in the U.S. in 1981, but these cases provide little information about the source of this disease. Now there is clear evidence that AIDS is caused by a virus known as HIV. So to find the source of AIDS we need to find the origin of HIV. 

The origin of HIV is not just about academic problems, because not only understand where it came from the virus but also how this virus is grown to be important to develop an HIV vaccine and more effective treatment. Also, knowledge about how the AIDS epidemic arose be important in determining the shape of the epidemic in the future as well as develop education and prevention programs are effective.

This type of virus is HIV?

HIV is part of a family or a group of viruses called lentiviruses. Lentiviruses such as HIV is found in a wide range of non-human primates. Another lentivirus, known collectively as the monkey virus known as SIV (simian immunodeficiency virus) in which the subscript indicates the origin of species. 

So where HIV originated? Is HIV originated from SIV?

It is now generally accepted that HIV is a descendant of SIV. Specific SIV types similar to HIV-1 and HIV-2, two types of HIV.

For example, HIV-2 can be equated with the SIV found in sooty mangabey monkeys (SIVsm), sometimes known as green monkeys originating from western Africa.

The more virulent strains of HIV, namely HIV-1, until recently very difficult to be classified. Until 1999, the most similar is known SIV that infects chimpanzees (SIVcpz), but there are significant differences between SIVcpz and HIV.

So what happened in 1999? Are chimps now known as the origin of HIV?

In February 1999 it was announced that a group of researchers from the University of Alabama, in the U.S., has studied frozen tissue from a chimpanzee and find the type of virus (SIVcpz) is almost identical to HIV-1. Chimpanzees are from sub-group of chimpanzees known as Pan troglodyte troglodyte who once common in west-central Africa.

The researchers assert that this shows chimpanzees are the source of HIV-1, and this virus at some point crossed species from chimpanzees to humans. However, it is not clear whether the chimpanzee is the original source of HIV-1 because chimpanzees are rarely infected with SIVcpz. Therefore there is a good possibility chimps and humans are infected from a third party, namely a primate species that are still not recognizable. In any case, at least need two separate transfer to humans.

How is HIV can cross the species?

It has long been known that certain viruses can pass from animals to humans, and this process is known as zoonosis.

Researchers from the University of Alabama suggests that HIV can cross over from chimpanzees as chimpanzees kill and eat human flesh.

Several other theories are debated opinion that HIV moved in iatrogenic (caused by medical negligence party), for example through medical experiments. One well-circulated theory is that polio vaccines played a role in this movement, because the vaccine made using monkey kidneys.

But what is important in various kinds of theory is the question of when the transfer took place.

Is there a fact when the transfer took place?

Over the last few years allows not only to determine whether HIV is present in the blood, but also determine the virus subtype. Research on the virus subtype, of HIV infection in early cases may give clues about when HIV first attack humans and subsequent developments.

Three of the earliest HIV infection are as follows:

Examples of plasma (blood fluid) taken from an adult male who lived in the Democratic Republic of Congo in 1959.
HIV found in tissue samples from an African-American youth who died in St. Louis, USA, 1969.
HIV found in tissue samples from a Norwegian sailor who died around 1976.
The analysis conducted in 1998 on plasma samples from 1959 suggests that HIV-1 into humans around the 1940s or early 1950s, earlier than previously thought. Other scientists predict even longer, probably about 100 years ago or more.

What is known in which HIV in humans appear?

Now many people think because of HIV seen develop from one type of SIV found in chimpanzees in West African type, this means that HIV first appeared in humans in there. Then presumed that HIV spread from Africa to the world.

However, as discussed above, chimpanzees are not necessarily the original source of HIV and there is a possibility the virus crossed over to humans, more than one occasion. So perhaps also HIV arise at the same time in both South America and Africa, or even appear in the American continent before appearing in Africa.

We may never know exactly when and where the virus first appeared, but certainly at some time in the mid 20s this century, HIV infection in humans developed into a worldwide epidemic that is currently better known as AIDS .

What caused the epidemic spread of a sudden?

There are several factors that can support the deployment was so sudden, including international travel, blood industry, and drug use is widespread.

International Travel

The role played by international travel in the spread of HIV is highlighted in the case now known as 'Patient Zero' (original patients). Patient Zero was a Canadian citizen airplane steward named Gaëtan Dugas and the frequent travel throughout the world.Analysis of several cases of early AIDS-infected persons showed that these are people who have sex either directly or indirectly by this steward. These cases are found in several U.S. cities this shows the role of international travel in the spread of HIV. It also suggests that this disease may be caused by a substance spreader.

Blood Industry

While blood transfusions became a routine part of medical treatment, the blood industry to meet the demand for blood also increases. In some countries like the U.S., people who get paid to donate blood, including intravenous drug users. The blood obtained was then sent to the entire world. Also, in the late 1960s began to take advantage of hemophiliacs blood clotting, called Factor VIII.

To produce the clotting substances, the blood collected from thousands of donors that increase the likelihood of these products contaminated with HIV. Because Factor VIII spread around the world, there are likely many hemophiliacs exposed to new infections.

Use of Drugs

In the 1970s found increased availability of heroin along with the Vietnam war and other conflicts in the Middle East, which encourages the growth of injecting drug use.Increasing the provision and development tools, disposable plastic syringes and the construction of shooting gallery (where injecting drugs) where people can buy drugs and rent equipment to be another way of spreading the virus.

What other theories about the origin of HIV?

Other theories put forward about the origin of HIV, including the many conspiracy theories. Some people with HIV impressive made by the CIA, although others consider that the genetically engineered HIV. 

Original article: The Origin Of HIV

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Sinkhole the Strange hole

A sinkhole, also known as a sink, shake hole, swallow hole, swallet, doline or cenote, is a natural depression or hole in the Earth's surface caused by karst processes — the chemical dissolution of carbonate rocks[1] or suffosion processes[2] for example in sandstone. Sinkholes may vary in size from 1 to 600 meters (3.3 to 2,000 ft) both in diameter and depth, and vary in form from soil-lined bowls to bedrock-edged chasms. Sinkholes may be formed gradually or suddenly, and are found worldwide. The different terms for sinkholes are often used interchangeably. [3]Contents  

A special type of sinkhole – formed by rainwater leaking through the pavement and carrying dirt into a ruptured sewer pipe.

Sinkholes may capture surface drainage from running or standing water, but may also form in high and dry locations.

The mechanisms of formation involve natural processes of erosion or gradual removal of slightly soluble bedrock (such as limestone) by percolating water, the collapse of a cave roof, or a lowering of the water table. Sinkholes often form through the process of suffosion. Thus, for example, groundwater may dissolve the carbonate cement holding the sandstone particles together and then carry away the lax particles, gradually forming a void.

Occasionally a sinkhole may exhibit a visible opening into a cave below. In the case of exceptionally large sinkholes, such as Minyé sinkhole in Papua New Guinea or Cedar Sink at Mammoth Cave National Park, USA, a stream or river may be visible across its bottom flowing from one side to the other.

Sinkholes are common where the rock below the land surface is limestone or other carbonate rock, salt beds, or rocks that can naturally be dissolved by circulating ground water. As the rock dissolves, spaces and caverns develop underground. These sinkholes can be dramatic because the surface land usually stays intact until there is not enough support. Then, a sudden collapse of the land surface can occur.

Sinkholes also form from human activity, such as the rare but still occasional collapse of abandoned mines in places like West Virginia, USA. More commonly, sinkholes occur in urban areas due to water main breaks or sewer collapses when old pipes give way. They can also occur from the overpumping and extraction of groundwater and subsurface fluids. They can also form when natural water-drainage patterns are changed and new water-diversion systems are developed. Some sinkholes form when the land surface is changed, such as when industrial and runoff-storage ponds are created; the substantial weight of the new material can trigger an underground collapse of supporting material, thus, causing a sinkhole.

Sinkholes are usually but not always linked with karst landscapes. In such regions, there may be hundreds or even thousands of sinkholes in a small area so that the surface as seen from the air looks pock-marked, and there are no surface streams because all drainage occurs sub-surface. Examples of karst landscapes dotted with numerous enormous sinkholes are Khammouan Mountains (Laos) and Mamo Plateau (Papua New Guinea). The largest known sinkholes formed in sandstone are Sima Humboldt and Sima Martel in Venezuela.

The most impressive sinkholes form in thick layers of homogenous limestone. Their formation is facilitated by high groundwater flow, often caused by high rainfall - such high rainfall causes formation of the giant sinkholes in Nakanaï Mountains, New Britain island in Papua New Guinea. On the contact of limestone and insoluble rock below it there form powerful underground rivers which may create large underground voids.

In such conditions have formed the largest known sinkholes of the world, like the 662-metre (2,172 ft) deep Xiaozhai tiankeng (Chongqing, China), giant sótanos in Querétaro and San Luis Potosí states in Mexico and others.

Unusual processes have formed the enormous sinkholes of Sistema Zacatón in Tamaulipas (Mexico) - here more than 20 sinkholes and other karst formations have been shaped by volcanically heated, acidic groundwater. This has secured not only the formation of the deepest water-filled sinkhole in the world - Zacatón, but also unique processes of travertine sedimentation in upper parts of sinkholes, leading to sealing of these sinkholes with travertine lids.

The state of Florida in the USA is known for having frequent sinkholes, especially in the central part of the state. The Murge area in southern Italy also has numerous sinkholes. Sinkholes can be formed in retention ponds from large amounts of rain.

Sinkholes have been used for centuries as disposal sites for various forms of waste. A consequence of this is the pollution of groundwater resources, with serious health implications in such areas. In contrast, the Maya civilization sometimes used sinkholes in the Yucatán Peninsula (known as cenotes) as places to deposit precious items and sacrifices.

Many sinkholes are found in Northern Michigan. These are prominent in Alpena County in Northeast Michigan. In Lachine, Michigan there are five sinkholes that are found to be very deep and within 2 miles (3.2 km) from each other. Alpena's visitor information cites their sinkholes as an attraction for visitors to the area. In August 1998 a 16 year old Alpena boy survived a 200 feet (61 m)+ fall in an open sinkhole 0.75 miles (1.2 km) from Leer road in Lachine, Michigan.A majority of sinkholes in Alpena are also found underwater. Many divers explore these on a regular basis.

When sinkholes are very deep or connected to caves, they may offer challenges for experienced cavers or, when water-filled, divers. Some of the most spectacular are the Zacatón cenote in Mexico (the world's deepest water-filled sinkhole), the Boesmansgat sinkhole in South Africa, Sarisariñama tepuy in Venezuela, and in the town of Mount Gambier, South Australia. Sinkholes that form in coral reefs and islands that collapse to enormous depths are known as Blue Holes, and often become popular diving spots.

The overburden sediments that cover buried cavities in the aquifer systems are delicately balanced by groundwater fluid pressure. The water below ground is actually helping to keep the surface soil in place. Groundwater pumping for urban water supply and for irrigation can produce new sinkholes in sinkhole-prone areas. If pumping results in a lowering of groundwater levels, then underground structural failure, and thus, sinkholes, can occur.

from http://en.wikipedia.org/wiki/Sinkhole 

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