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.
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. |
 |
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.