From the guidelines, as from January 2013: "People do not need to wait for permission to log your EarthCache. Requiring someone to wait is not supported by the EarthCache guidelines. People should send their logging task answers to you, then log your EarthCache. When you review their logging task answers, if there is a problem, you should contact them to resolve it. If there is no problem, then their log simply stands."
Covão Cimeiro
Covão Cimeiro is an amphitheatre with sheer walls. It is one of the most spectacular examples of a glacial cirque in the Estrela Mountain range of NE central Portugal. This cirque; a huge depression flanked by Cântaro Magro (a flatish topped peak and one of the mythic destinations of the Estrela Mountain) shows a basal section that is polished by the abrasion of the ice sheets.
The covão’s morphology is such that it has a central depression loosely termed a “belly button” (ombilic in french) – In the Estrela Mountain range it is these depressions that are known by the local term “Covão”). Downstream the covão is partially closed by a glacial bar (verrou in french). - Observe the image below:
Check out this link of a 360º view of this cirque.
What is a cirque?
A cirque is an amphitheatre-like valley (or valley head) of glacial origin, formed by glacial erosion at the head of the glacier. Cirques are typically partially surrounded by steep cliffs. The highest cliff is often called a headwall. Many glacial cirques contain tarns dammed by glacial till. Cirques form in conditions which are favorable; which in the northern hemisphere includes the north-east slope being in shade and away from prevailing winds. These areas are sheltered from heat, and so, they encourage the accumulation of snow.
Cirques form in conditions which are favorable for glacier formation - where snow can accumulate into a thick and large mass. If the accumulation of snow increases, the snow transforms into glacial ice. The process of nivation follows (where a hollow in a slope may be enlarged by freeze-thaw weathering and glacial erosion). Eventually, this hollow can become big enough so that glacial erosion intensifies. Debris (or till) in the ice may also abrade (glacial abrasion) the bed surface; should ice move down a slope it would have a ‘sandpaper effect’ on the bedrock beneath on which it scrapes.
Eventually, the hollow can become a large bowl shape in the side of the mountain, with the headwall being weathered by constant freezing and thawing, and eroded by plucking. The basin will become deeper if it continues to become eroded by abrasion. Should plucking and abrasion continue, the dimensions of the cirque will increase, but the proportion of the landform would remain roughly the same.
The EarthCache:
Knowing that the cirques (covões in PT) are formed by moving ice masses, you have to estimate the thickness of the ice mass that created this cirque. To do this, park at the cache coordinates and CAREFULLY observe the Covão Cimeiro and the adjacent sheer walls. Send me the answer by e-mail to validate your log. Thanks and enjoy the views.
Covão Cimeiro
O Covão Cimeiro é um anfiteatro de paredes abruptas e trata-se de um dos mais espectaculares exemplos de circo glaciário da Serra Da Estrela. O seu fundo apresenta-se sobreescavado e apresenta um obstáculo rochoso no seu sector terminal. É um exemplo típico de paisagem glaciar, denominando-se a área deprimida por ombilic (“umbigo” ou depressão gradual) que na Serra da Estrela é designado por covão glaciário e a convexidade rochosa que o fecha a jusante é normalmente designada por verrou (“ferrolho” ou barra rochosa). Vejam a imagem no topo da página.
Neste covão é possível observar o aspecto quase polido da sua superfície devido à abrasão causada pela massa de gelo que ali passou.
Circos glaciares
Um circo glaciar é um vale que apresenta uma geomorfologia em forma de anfiteatro e são normalmente formados à cabeça do glaciar. No hemisfério norte, formam-se normalmente nas encostas viradas a NE que são as encostas protegidas dos ventos e calor solar uma vez que estão à sombra. Aqui e nestas condições acumula-se neve. Se a acumulação de neve se mantiver, os processos de erosão basal intensificam-se criando uma bacia. A bacia tende a reter a sua forma mesmo aumentando de tamanho.
Os circos glaciares são pontos de alimentação de glaciares estando hoje, em climas mais amenos, cheios de água.
A EarthCache:
Para poderem logar um found nesta EC estacionem nas coordenadas da cache, observem (com muito cuidado) o Covão Cimeiro e estimem qual a espessura da massa glaciar que por ali passou. Enviem-me as respostas via o meu e-mail. Obrigado e boas fotos.
The most exciting way to learn about the Earth and its processes is to get into the outdoors and experience it first-hand. Visiting an Earthcache is a great outdoor activity the whole family can enjoy. An Earthcache is a special place that people can visit to learn about a unique geoscience feature or aspect of our Earth. Earthcaches include a set of educational notes and the details about where to find the location (latitude and longitude). Visitors to Earthcaches can see how our planet has been shaped by geological processes, how we manage the resources and how scientists gather evidence to learn about the Earth. To find out more click HERE.
