GC40M5K Mahe Island EarthCache (Earthcache) in Seychelles created by cincol

GC40M5K ▼

A cache by cincol Message this owner

Hidden : 11/2/2012

Difficulty:

Terrain:

Size: Size: not chosen (not chosen)

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Geocache Description:

MAHE ISLAND EARTHCACHE

For the sake of modern GPSr's and other applications available nowadays I have placed the questions and other details first.

This EarthCache is more about EXPERIENCING the environment and OBSERVING what is around you rather than a theoretical lesson in geology. It is my wish that you leave this place being wiser about the earth we live on and that you have had a positive experience being here. Please note that this might not be easy to access with small children and I also recommend that you wear decent shoes or go barefoot. "Flip-flops" are NOT recommended at all as climbing on rocks can be dangerous. Enjoy the beautiful little beach nearby for a swim and some excellent snorkelling. We even saw a decent sixed moray eel under the rocks here!

Learning Points that require answers in order to qualify for logging this EarthCache. Send answers to cincolcc(at)gmail.com in order to qualify. Please note that logs not supported by an e-mail to Cache Owner will be deleted as per earthcache.org and geocaching.com requirements.

Carefully examine the rock at GZ and comment on the composition thereof. It is smooth or rough? Can you see anything embedded in the rocks perhaps - what do you see?
What do you thing was responsible for the shape of the rock at GZ? Explain why you think your answer is correct.
Comment on any other granite outcrops you have seen in Seychelles and how they might differ to this site.
What object do you observe at a bearing of 245 degrees?
What structure(s) do you see at a bearing of 180 degrees?

VIEW FROM GROUND ZERO

SOME DETAILS ABOUT THE EARTHCACHE

The Seychelles is an island state in the western Indian Ocean, approximately 1,600 km east of the African countries of Kenya and Tanzania and NW of Madagascar.. The Seychelles consists of more than 90 widely scattered islands, most of which are uninhabited. The main island is Mahe with mountains reaching up to 1,000 m. The other main islands are Praslin and La Digue to the North West.

The Seychelles is part of the granitic Mascarene Plateau which broke off from the Indian Plate about 65 mya. This rift formation is associated with the Réunion hotspot which is also responsible for Réunion Island and the Deccan Traps in India.

The principal islands of the Seychelles, the Mahe and Praslin-La Digue islands, are made up mainly of Neoproterozoic (Pan-African) granites and hornblende granites, intruded by dolerites and olivine dolerites. The continental crust of the Seychelles is widely regarded as a continental fragment left behind when the continent of Gondwana broke up and the Indian Ocean widened. Most of the smaller islands in the Seychelles are made up of coral atolls or calcareous sands built on reefs.

Granite is a common widely occurring type of intrusive, igneous rock which is granular and crystalline in texture. This rock consists mainly of quartz, mica, and feldspar. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. Granites can be pink to gray in color, depending on their chemistry and mineralogy. By definition, granite is an igneous rock with at least 20% quartz by volume. Granite differs from granodiorite in that at least 35% of the feldspar in granite is alkali feldspar; it is the alkali feldspar that gives many granites a distinctive pink color. Outcrops of granite tend to form tors and rounded massifs. Granite is usually found in the continental plates of the Earth's crust. Granite is nearly always massive (lacking internal structures), hard and tough, and therefore it has gained widespread use as a construction stone.

Granite is currently known only on Earth, where it forms a major part of continental crust. Granite often occurs as relatively small, less than 100 km² stock masses (stocks) and in batholiths that are often associated with orogenic mountain ranges. Small dikes of granitic composition called aplites are often associated with the margins of granitic intrusions. In some locations, very coarse-grained pegmatite masses occur with granite. Granite has been intruded into the crust of the Earth during all geologic periods, although much of it is of Precambrian age. Granitic rock is widely distributed throughout the continental crust and is the most abundant basement rock that underlies the relatively thin sedimentary veneer of the continents.