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A marmita do Anha

A cache by joom Send Message to Owner Message this owner
Hidden : 03/21/2016
Difficulty:
2.5 out of 5
Terrain:
2.5 out of 5

Size: Size: other (other)

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Geocache Description:


Perguntas para responder - questions to answer

Para reclamar esta earthcache deverá enviar-me, através do meu perfil e antes de qualquer registo, as respostas às seguintes questões. Se algo estiver incorrecto será contactado. Não é necessário esperar por qualquer autorização.

Nas coordenadas da earthcache deverá ver uma marmita de gigante erodida.

1 - Qual é o seu diâmetro aproximado?

2 - Qual é a sua profundidade aproximada? Nota: não é a profundidade do rio mas sim a altura desde a parte mais alta da marmita e o seu fundo.

3 - Quantos sãos os níveis de estacionamento dinâmico? (os diferentes degraus da marmita)

4 - Visto do centro da marmita em que ponto cardeal está a maior parede da marmita?

5 - O processo de formação da marmita já terminou? Explique a sua resposta.

Obrigatório:

Uma foto por cada registo. Ou claramente identificado no ponto zero ou senão o desejar uma foto na zona do ponto zero em que apareça o nick, a data da visita e um pé. Por favor não revele as respostas com essa foto. Obrigado pela visita.

 

To claim this earthcache one should send me, through my profile and before any found log, the answers to the following questions. If something is incorrect I'll contact you. There is no need to wait for any authorization.

 

At the earthcache coordinates you should see an eroded giant pothole.

1 - What is its approximate diameter?

2 - What is its approximate depth? Please note that it isn't the river's depth but the measurement from the tallest pothole wall to the bottom.

3 - How many are the dynamic erosion platforms? (different steps inside the pothole)

4 - From the pothole center, and regarding north, where is the largest pothole's wall?

5 - Is the pothole's formation concluded? Explain your answer.

Mandatory:

A photo for each log. Or clearly identified (a selfie) at ground zero or if you don’t wish a photo at ground zero that shows your nickname, date of visit and a foot. Please do not reveal the answers with this photo. Thank you for your visit.

 


A marmita

As marmitas de gigante ou marmitas turbilhonares, são depressões, mais ou menos arredondadas, com dimensões bastante variáveis, existentes no leito rochoso de alguns rios e no fundo das quais se encontram seixos e areias.

As marmitas parecem ter origem em irregularidades existentes nos leitos rochosos dos rios. Estas irregularidades retêm nas suas proximidades alguns seixos. A acumulação de seixos vai provocar um movimento turbilhonar da água e consequentemente um movimento circular das partículas. Pouco a pouco, devido ao atrito, as partículas vão escavando depressões mais ou menos circulares, no leito do rios, dentro das quais ficam aprisionadas. Com o decorrer do tempo, as depressões aumentam de dimensões e os seixos que estão no seu interior tendem a ficar esféricos.

Como são formadas as marmitas:

É formado um redemoinho de água do rio em torno de irregularidades formando assim correntes verticais estacionárias Algumas rochas são forçadas nas depressões e assim desgastam a parte oca. Estas rochas são chamadas moedoras. O processo continua aumentando o buraco tanto em largura como em profundidade.


Apesar de existirem marmitas com vários metros de diâmetro e profundidade, as mais frequentes possuem dimensões na ordem dos decímetros.

Fontes:

http://www.dct.uminho.pt/pnpg/trilhos/pitoes/paragem6/marmitas.html
https://en.wikipedia.org/wiki/Giant's_kettle
http://camppemi.com/category/newsletters/newsletters-2014/
Inventariação do património geomorfológico do litoral do concelho de Viana do Castelo


The pothole

A giant's kettle, also known as a giant's cauldron or pothole, is a cavity or hole which appears to have been drilled in the surrounding rocks by eddying currents of water bearing stones, gravel, and other detrital matter.

Potholes vary in size from a few inches to several feet in depth and diameter. They most commonly occur in shields, where there are ancient rocks (granite, gneiss) with different resistances to erosion, so strong pebbles can fall into small cavities in stream bottoms and swirl, making the cavities wider and deeper. The hardness of the pebbles must be the same or higher than the rock at the bottom of stream where the kettle is forming. In areas where there are diamonds and quartz pebbles, the hardness of these carve potholes and sometimes remain trapped in the bottom of them.

How potholes are created:

River water is swirled around in irregularities in the river bed creating vertical eddies. Rocks get swept into the small depressions and abrade the hollow. These rocks are called grinders. The process continues deepening and enlarging the pothole.


Giant's kettles can also be formed while the surface is covered by a glacier. Water, produced by the thawing of the ice and snow, forms streams on the surface of the glacier, which, having gathered into their courses a certain amount of morainic debris, finally flow down a crevasse as a swirling cascade or moulin. The sides of the crevasse are abraded, and a vertical shaft is formed in the ice. The erosion may be continued into the bed of the glacier; and, the ice having left the district, the giants kettle so formed is seen as an empty shaft, or as a pipe filled with gravel, sand or boulders. Such cavities and pipes afford valuable evidence as to the former extent of glaciers.

Fontes:

http://www.dct.uminho.pt/pnpg/trilhos/pitoes/paragem6/marmitas.html
https://en.wikipedia.org/wiki/Giant's_kettle
http://camppemi.com/category/newsletters/newsletters-2014/
Inventariação do património geomorfológico do litoral do concelho de Viana do Castelo


Por favor não partilhe as respostas. Para que continuem a existir earthcaches junte ao registo uma fotografia desse dia no ponto zero. Assim ajuda a acabar com as visitas fantasmas a lembrar o Walter Mitty.
Please do not share the answers. To make sure that earthcaches endure append to your log a photo of the day at ground zero. It helps to end ghost visits that resemble Walter Mitty.

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75 Logged Visits

Found it 72     Didn't find it 1     Publish Listing 1     Owner Maintenance 1     

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Coordinates are in the WGS84 datum

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