EarthCache

A xenolith at the beach

A cache by global trekkers Send Message to Owner Message this owner
Hidden : 9/28/2010
In Lisboa, Portugal
Difficulty:
1 out of 5
Terrain:
3.5 out of 5

Size: Size: not chosen (not chosen)

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Geocache Description:


A xenolith is a rock fragment which becomes enveloped in a larger rock during the latter's development and hardening. In geology, the term xenolith is almost exclusively used to describe inclusions in igneous rock during magma emplacement and eruption. Xenoliths may be engulfed along the margins of a magma chamber, torn loose from the walls of an erupting lava conduit or explosive diatreme or picked up along the base of a flowing lava on Earth's surface.

 xenolith1

Although the term xenolith is most commonly associated with igneous inclusions, a broad definition could include rock fragments which have become encased in sedimentary rock. Xenoliths are sometimes found in recovered meteorites.

To be considered a true xenolith, the included rock must be identifiably different from the rock in which it is enveloped. xenolith2

Source: wikipedia

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This cache will take you to Praia da Ursa, where the granites of the Sintra Massif formed in the upper Cretacious meet the Jurassic limestones. At the published coordinates you will find a limestone xenolith embedded in granite.
Esta cache vai levá-lo à Praia da Ursa, onde os granitos do maçico de Sintra formados no Cretáceo Superior se encontram com os calcários do Jurássico. Nas coordenadas publicadas irá encontrar um xenólito de calcário envolvido por granito.

 
To claim this Earthcache, you need to answers the following questions:
Para reclamar esta Earthcache, terá de responder às seguintes questões:

 
1- What geometric form does this xenolith resemble?
1- Qual a forma geométrica a que o xenólito mais se assemelha?

2- What is the height of the xenolith?
2- Qual a altura do xenólito?

3- What is the color of the oldest rock?
3- Qual a cor da rocha mais antiga?

4- What is the direction from this geological feature to the famous rock that gives name to the beach?
4- Qual a orientação, a partir do xenólito, até à famosa rocha que dá nome à praia?

Email me your answers through my GC profile and I will contact you to allow/deny the log of this cache.
Envie-me um email com as suas respostas através do perfil do GC e será contactado para logar, ou não, a cache.

Attention: No photos of the xenolith on the logs. Logs containing photos of this geological feature (accidentally or otherwise) will be deleted and the geocacher asked to re-log.
Atenção: Nada de fotos do xenólito nos logs. Logs que contenham fotos deste fenómeno geológico (acidentalmente ou não) serão apagados e o geocacher em questão será contactado para logar novamente.

For a detailed reading about xenoliths, in particular the context of their formation in the Sintra massif, I strongly recommend you to visit Trapped! - DP/EC49.
Para uma leitura detalhada sobre xenólitos, em especial sobre o contexto da sua formação no maciço de Sintra, recomenda-se vivamente a visita à Trapped! - DP/EC49.

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Current Time:
Last Updated: on 6/22/2017 7:27:20 AM Pacific Daylight Time (2:27 PM GMT)
Rendered From:Unknown
Coordinates are in the WGS84 datum