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This cache has been archived.

lynx pardinus: Due to the archaelogical sensitivity of the surrounding area, I decided that it would be unwise to have people searching for a container and lifting all the rocks in the surrounding area.

I am still pursuing to list a different cache type in this place but for now this will be archived.

Thanks to all the people that warned me about this area sensitivity and importance and that presented all kind of ideas to enable this cache.

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Penedo do Lexim

A cache by lynx pardinus Send Message to Owner Message this owner
Hidden : 06/19/2005
Difficulty:
2 out of 5
Terrain:
2.5 out of 5

Size: Size: regular (regular)

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Geocache Description:

O Penedo do Lexim é uma das antigas chaminés vulcânicas extintas, do chamado complexo vulcânico de Lisboa, estando actualmente classificado como de interesse público.

Penedo do Lexim (Lexim’s Rock) is one of the extinct volcanic chimneys of the so called Lisbon’s volcanic complex. It is nowadays classified as of public interest.

Com cerca de 230 metros de altitude no seu ponto mais elevado, esta elevação teve origem no final do período Mesozóico, há cerca de 72 milhões de anos, num período de forte actividade magmática (‘Volcanic chart’ figure). O que hoje em dia se observa corresponde a parte da antiga chaminé vulcânica, nomeadamente o antigo material magmático solidificado, mais resistente, que sobreviveu à erosão natural dos elementos (e não só, uma vez que este local chegou a funcionar como pedreira…) dos últimos 72 milhões de anos (‘Erosion chart’ figure). Estudos efectuados indicam que a chaminé vulcânica originalmente atingia os 30 metros de diâmetro e cerca de 2000 metros de profundidade.

O basalto marca naturalmente a sua presença, salientando-se a existência de prismas de secção hexagonal (resultado do processo de arrefecimento magmático) e de fenocristais como a olivina e piroxena.

A cache está nas coordenadas acima, de onde podem observar um destes blocos basálticos com formas prismáticas hexagonais. No entanto, não deixem de visitar a área de exploração da pedreira (N38º 53.549 W009º18.670) e de admirar a vista do topo do penedo (N38º53.529 W009º18.677) – facilmente acessível.

Olhando do alto do Penedo, e apesar da geografia relativamente acidentada que o rodeia (toda a zona Oeste é uma área de baixa-montanha), a paisagem bucólica que observamos (os campos verdes, a aldeia de Cheleiros e a estrada ao fundo, as quintinhas a rodearem-nos, as turbinas silenciosas de energia eólica) leva-nos a pensar que esta paisagem está assim desde sempre. Que, se houve alterações, estas foram pequenas e menosprezáveis. Mas lembrem-se, estão apenas sobre um dos muitos vulcões que, na realidade, ajudaram a formar esta paisagem há mais de 70 milhões de anos. Se, por acaso passassem por aqui por essa altura, iriam encontrar uma paisagem muito diferente, que vos provaria que o chão que pisam diariamente é apenas uma parte de um todo em constante mudança, mas a uma escala temporal consideravelmente maior do que a memória dos seres humanos pode abarcar.

Measuring 230 metres high on its peak, this hill originated on the end of the Mesozoic period, around 72 Million years ago, in a strong volcanic activity period (‘Volcanic chart’ figure). What we can see nowadays is part of the remaining volcanic chimney, namely the solidified magma material, stronger, that survived the natural erosion process (and the former stone quarry that operated in this place…) of the last 72 Ma. (‘Erosion chart’ figure). Studies indicated that this chimney originally was 30 metres in diameter and 2000 metres deep.

Basalt shows its presence here, and you should observe hexagonal basalt prisms (resulting from the magma cooling process) and several crystals.

The cache is in the above coordinates, where you can better appreciate one of these hexagonal prismatic basaltic boulders. Still, don’t miss the stone quarry area (N38º 53.549 W009º18.670) and admire the scenic view from the peak (N38º53.529 W009º18.677) – easily accessible.

Taking a look around from the top of the Lexim’s Rock, and despite the low-mountain area that surrounds us, the calm and colourful scenic view we admire (the green fields, Cheleiros village down in the valley, the main road some distance away, the little farms all over the place, the silent power plant wind-mills) may lead us to think we are facing a landscape that has been like so forever. That, if any change would have happened, those were only small and neglectable. But remember you are only on top one of the many volcanoes that actually shaped this landscape over 70 Million years ago. If by any chance you would have passed by then, you would have found a very different scenic view, that would have made you remember that the ground in which you step daily is par of a ever-changing globe – only at a timescale incomparably larger than our memory can even understand.

Information and charts extracted from (visit link)

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