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Earthcache Ronda peridotite by J_Rover (2/1)
N36° 35.124  W5° 04.160 (WGS84)
UTM  30S   E 314872  N 4050874
Use waypoint: GC1C9X8
Size: Not chosen Not chosen    Hidden on 16-5-2008
In Andalucía, Spain
Difficulty:  2 out of 5   Terrain:  1 out of 5 		   


An educational cache in your trip to Ronda / Un cache educativo en su viaje a Ronda.

Ronda peridotites

When you travel to Ronda from the Costa del Sol, following the A397 Highway, as soon as you have crossed the first kilometers you will find yourself immersed between dark reddish mountains. You have entered the dominions of Sierras Bermejas (Reddish Mountains). As all the road is virtually carved on rocks you can easily observe them on each bank.

They are dark, and sometimes, almost metallic shining rocks. Its coloration varies from red-brown to intense dark green.... These uncommon rocks seem as they are saying to us, in some way, that they do not belong to this place. And indeed thus is. They are peridotites and you are now crossing one of the major superficial outcrops of these rocks that exist in our planet.

Peridotite is a dense (~ 4 g/cm3), coarse-grained igneous rock, consisting mostly of the minerals olivine and pyroxene. Peridotite is ultramafic and ultrabasic, as it contains less than 45% silica and it is high in magnesium, with appreciable iron. They are highly unstable, because olivine reacts quickly with water in a process in which pyroxenes and olivines are converted to green serpentine.

Peridotite is the dominant rock of the upper part of the Earth's mantle, however the rocks of the peridotite family are very uncommon at the Earth's surface. This extraordinary rocks, formed much deeper within the Earth, has emerged to the surface thanks to the incredible pushes derived from the collision between the plates of Europe and Africa in the last Orogeny.

A good observation point is the published WP where it is possible to park your car, touch and observe them to your pleasure. Also you can satiate your thirst in a spring that flows, at about 100 m. from there, between these fabulous and strange rocks. A few Kms later (Km.20) suddenly peridotites disappear and the landscape again begins to be white-limestone. You have returned to the dominions of the Sierras Blancas (White Mountains). Do not lost it!

In order to register the cache you must mail me the answers to the following questions:
  1. How many will weigh a block of ~ 1 m3 like these that you will be able to observe, fallen, just in the edge of the road?
  2. How deep beneath the surface of the Earth it is believed that is the origin of these rocks?
  3. What Orogeny made this rocks arise to the Earth’s surface?

After obtaining mail authorization, upload a photo of yours with some peridotite and/or in the near spring and write a Log describing your experience.

Si viaja Vd. a Ronda desde la Costa del Sol siguiendo la carretera A397, apenas recorridos los primeros kilómetros se encontrará inmerso entre montes de coloración rojiza muy oscura. Está Vd. en el dominio de las Sierras Bermejas. Dado que toda la carretera está tallada a pico le será muy fácl observar en cada talud de la misma unas inquietantes rocas.

Son oscuras, brillantes, en ocasiones casi metálicas. Su coloración varía desde el rojo casi negro a un intenso verde oscuro .... Estas extrañas rocas parece que nos estén diciendo, de algún modo, que no pertenecen a dicho lugar. Y efectivamente es así. Son peridotitas y Vd. está recorriendo uno de los mayores afloramientos superficiales de dichas rocas que existen en todo el planeta.

La peridotita es una densa (~ 4 g/cm3) roca ígnea de grano grueso. Está compuesta de olivino y piroxeno básicamente. Es una roca ultramáfica y ultrabásica, dado que contiene menos del 45 % de sílice, con alto contenido de magnesio y bastante hierro. Son altamente inestables pues el olivino reacciona muy rápido con el agua en un proceso en el que los piroxenos y olivinos se convierten en serpentina verde.

La peridotita es la roca dominante en el manto superior de la Tierra, sin embargo son muy raras en la superficie del planeta. Estas extraordinarias rocas, creadas a gran profundidad, han emergido a la superficie merced a los increibles empujes derivados de la colisión de las placas europea y africana en la última orogenia.

Un buen punto de observación es el WP inicial donde se puede detener el coche, observarlas y tocarlas a placer. También puede refrescarse y saciar su sed en un nacimiento de agua que mana, a unos 100 m. de alli, desde el interior de la montaña formada por estas fabulosas y extrañas rocas. Unos Kms más adelante (Km.20) súbitamente desaparecen las peridotitas y el paisaje vuelve a ser otra vez blanco-calizo. Ha pasado a los dominios de las Sierras Blancas .. ¡no se lo pierda!

Para registrar el caché deberá escribirme y responder las siguientes cuestiones:
  1. ¿Cúanto pesará un bloque de ~ 1 m3 como los que podrá observar, caídos, al borde mismo de la carretera?
  2. ¿A qué profundidad dentro del planeta se estima que se han formado estas rocas?
  3. ¿Qué Orogenia las hizo aflorar a la superficie de La Tierra?

Después de conseguir mi autorización, cuelgue una foto suya con alguna peridotita y/o en el cercano manantial y escriba su Log describiendo su experiencia.

Additional Waypoints

PB1C9X8 - Peridotite border - Frontera
N 36° 37.559 W 005° 04.682

RP1C9X8 - Spring - Manantial
N 36° 35.217 W 005° 04.030


Additional Waypoints (2)
CodeNameTypeLinksCommentsDateCoordinatesDistance
PB1C9X8   Peridotite border - FronteraReference Point   Google Maps    18-5-2008   N 36° 37.559 W 5° 04.682 4,58 kms N
RP1C9X8   Spring - ManantialReference Point   Google Maps    18-5-2008   N 36° 35.217 W 5° 04.030 0,26 kms NE

Additional Hints (There are no hints for this cache)

Current at 30-6-2009

Found it 18-6-2009 by Sternenkriegerin
A very nice stop on our trip to Ronda. Thanks for the quick logging approval. We enjoyed the fresh cool water on this very hot day very much.

Found it 18-6-2009 by geo_tom
Found this one on our trip to Ronda. Great landscape and nice water. It seems to be popular with the locals, too, and we had to wait quite some time before we could fill our bottle...

Found it 15-6-2009 by falalillo
On the roundtrip over Andalucia together with omblo, we had a short Stop to admire this rocks.

Thanks for the Cache

Falalillo

Found it 15-6-2009 by omblo
With Falalillo on the way to Ronda. We were looking for this not very common cache - good place for a short picnic, and for me a flashback to geology studies.
Thanks for showing this interesting place!

Greetings from Germany,
omblo

Found it 11-6-2009 by TNT_Duck
Uma earthcache numa zona maravilhosa. Para além das magnificas paisagens, pude observar os peridotitos e deliciar-me com a água da nascente, bem fresquinha! TFTC

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Additional Hints (There are no hints for this cache)