Mull is constructed rather like a multi-tiered
wedding cake. Thick layers of basalt lava sit on top of a complicated
basement of much older rocks which peep out around the edges of Mull
rather like the silver base does on the lowest wedding cake tier.
Geologists love Mull because it has such a long and interesting history
(its oldest rocks on Iona are about 2000 million years old), and it has
unique structures and rocks found nowhere else in the world (such as the
Loch Ba Ring Dyke and felsite).
Mull has not always been in its present position
and form. Over geological time it has undergone enormous changes. Mull's
oldest rocks formed way south in the southern hemisphere and Mull (in
common with the British Isles) has gradually drifted northwards to its
present day position. (In the process of continental drift.) Its rocks
preserve details of the climatic zones that it passed through on its
northward journey. For example, if you stand on the rocky shore opposite
Inch Kenneth at Gribun you will be standing on sandstones deposited in a
desert region at the same sort of latitude and rather like the Persian
of Mull is made of lava poured out of fissure volcanoes when the North
Atlantic was forming and Mull was torn apart from its 'neighbour'
Greenland as the vast super-continent which once joined North America
and Europe divided. The molten lava which erupted from about 60 to 50
million years ago forms Mull's 'stepped' tablelands. Into these, at a
later stage, intrusions of other 'rocks formed by fire' took place,
forming the mountains of Mull's famous Central Igneous Complex. Volcanic
explosions and intense earthquakes shook Mull at that time and one of
the old fault lines, the Great Glen fault is still occasionally active.
final shape has largely been carved by huge glaciers which only melted
away from Mull 10,000 years ago leaving deep 'U' shaped valleys between
the mountains and long glaciated lochs both freshwater and marine. Mull
doesn't have any precious gems at the surface, but geologists know that
deep below Mull, in the earth's mantle there must be priceless minerals
at this spot, but the temperature at that depth would melt any drills
probing for them! Mull with its incredible history and unique rocks and
intrusions is a 'Mecca' for geologists who travel from all over the
world for field work.
All of the photographs have been taken by John Noddings
Information compiled by and shared with the courtesy of Rosalind Jones B.Sc. F.G.S.
Co-author of 'Earth and Space' Pub. Hodder and Stoughton ISBN
Mull in the Making By Rosalind Jones
The story of Mull & Iona's incredible 2800 million year
geological history. 'It caters for the non geologist drawn to Mull for the space and
solitude which the island affords.' - Eric Robinson,
Geology websites of interest include:
Isle of Mull Geology and Natural History;
Scottish Natural Heritage