The concept of Plate Tectonics offers an explanation for the formation, structure and inter-relationships of the Earth’s major landforms. The concept is based on a range of ideas, notably that the Earth’s crust is made up of a series of rigid ‘plates’ which rest and ‘float’ upon, and are created and destroyed by, materials from an underlying thick molten layer. Crust is created as lavas at mid-ocean ridges by a process known as sea-floor spreading. It is destroyed by a process known as ‘subduction’ in deep ocean trenches and at other margins between plates. The more unstable parts of the Earth’s surface are mainly along plate margins which are zones especially prone to structural pressures as a result of earthquakes and major geological 'faulting'.

The great attraction of the plate tectonics concept is that it offers a unified theory which successfully explains many aspects of geological history and the major landform features of the Earth. For example, the great mountain ranges, such as the Himalayas, Andes and Rockies , can be pictured as having been created by the buckling of crust where plates crash against one another.

Plate tectonics theory currently visualises the Earth as being composed of seven major, and several more minor, plates.   Over long periods of geological time - hundreds of millions of years, these plates have floated (very, very slowly) across the Earth's surface, on occasion coming together, at other times drifting apart, sometimes being near the equator, at other times being near the poles.

The geological history of Ireland over the last 500 million years can be interpreted in the context of the closing and opening of the Atlantic Ocean , events which are in turn linked to the changing   relations of the European and North American plates. Some time about 450 million years ago, part of the North American plate got torn away and joined to the plate belonging to the micro-continent of Avalonia, another plate. That section of North American plate (Laurentia) now forms much of north-west Ireland, an area with a very different rock base to the rest of Ireland, an area that comes from the plate containing Avalonia.

Later geological developments affecting   Ireland (and in north-west Europe) include the Caledonian mountain-building phase, tens of millions of years during which the North American and European plates clashed, and the re-opening of the Atlantic Ocean with sea-floor spreading associated with a great phase of volcanic activity about 40-60 million years ago. As these events unfolded, the area that is now Ireland drifted across the Earth's surface. About 400 million years ago, ' Ireland ' was well south of the equator, whereas, by about 300 million years ago, it was a little to the north.   Since then it has drifted slowly north to its present position.