Volcano Ahead EarthCache
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The above co ordinates take you to a car park with a notice board where you should manage to find the required information to answer the questions below.
Across the bay you will see Ben Hiant which is the flank of a volcano that formed 60 million years ago as the North Atlantic began to open and Europe and North America started to drift apart.
The headland to your left is Ardmore point, the northern tip of the the Isle of Mull. Most of Mull is made from a pile of lavas that poured out 60 million years ago from a volcano 25kms south of here.
Beyond Ben Hiant, to the north of Kilchoan, is a ring of hills that mark the magma chamber below a second volcano, active at the same time, that forms the western end of the Ardnamurchan peninsula. ( See GC4H89B The Land of the Rings )
The basalts of Antrim, including the Giants Causeway were erupted at the same time and in East Greenland, which was then only 900 km to the north west, there was an enormous outpouring of basalt which covered an area as large as Scotland to a depth of 7km in only 5 million years. This great outburst of volcanic activity was caused by a plume of solid but very hot rock that rose from very deep in the earths mantle. 100km below the surface the rising mantle rock partly melted, giving huge amounts of basalt magma.An opposing idea is that the movements of the tectonic plates triggered the release of magma from a layer in the upper mantle of the Earth that is already molten.
250 million years ago, North America, Europe and Africa were parts of a single supercontinent. A rift formed between what is now North America and North Africa that gradually widened. The new continents drifted apart and the space between became a shallow sea, the early Atlantic Ocean. 60 million years ago the North Atlantic began to open more rapidly, moving America and Europe even further apart. Today they are still drifting apart at 1cm a year and volcanic activity continues in Iceland which stands above the rift, now the Mid Atlantic Ridge. ( See GC1Z45X)
Ben Hiant is composed of a variety of rock types, formed at different times and in different ways. The hummocky land surface was carved by a glacier that scraped away rocks that varied in resistance to the moving ice, revealing a complex pattern of geology. The oldest rock of Ben Hiant, was deposited as sand and mud in a shallow sea more than 870 million years ago. The rocks were heated and compressed three times, most recently 430 million years ago. 60 million years ago,lavas from the Mull volcano flowed over the land surface and at the same time, to the west, magma was rising beneath the Ardnamurchan volcano causing the landscape to form a dome. The rocks of Ben Hiant were near the edge of this massive volcano dome. Rising volcanos are unstable and rocks were washed down the flanks to produce breccias.The summit of Ben Hiat is made of dolerite, a coarse grained form of basalt. The cone sheets mentioned on the diagram on the board are thinner sheets of basalt that form circles at the surface around the Ardnamrchan volcano.
To claim this earth cache please complete the following tasks and email your answers to us via our profile (please do not post your answers in your online log)
1 ~ According to the information board, what are you standing on and when did it arrive here ?
2 ~ How many other volcanos were also active in Western Scotland and where were they according to the board ?
3 ~ In your opinion which of the two theories regarding the birth of the Atlantic is more valid and why ?
4 ~ What is the name of the oldest rock type of Ben Hiant ?
5 ~ Using your GPS what is the elevation at the information board ?
6 ~ Now turning around and looking back at the road, you will see on the right hand side as you go towards Ardnamurchan lighthouse, that the road cutting has exposed some soil and rocks. Observe and describe the rocks you see exposed here, ( colour, smooth or rough, size & shape etc) and from what you have learnt here, explain what these rocks are ?
If I do not receive the answer, you may have your log deleted..... Educational guidelines for Earthcaches are set by Geocaching.com and GeoSociety.org (Earthcache) and have to be adhered to.
An optional task to post a photo of you or your gps with the bay or Ben Hiat in the background, but please be careful near the edge as it is a long drop down ~ children and dogs should be supervised here
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