The closest passive plate boundary to Ireland is the boundary between the African and Eurasian plate south of Portugal. When the plates eventually pass each other, the pressure is released in the form of an earthquake. When the plates move, the jagged edges of the plate boundaries snag and catch each other and can get jammed. This is when two plates slide past each other. See earthquakes, tsunami, and volcanoes for more on the effects of convergent plate boundaries (redirect to Topics section).Īlso known as strike-slip or transform boundaries. They are continually growing at an average rate of 1cm per year, this will be 10km in 1 million years. The Himalayas are an example of the collision of two continental plates where the Indian plate is crashing into the Eurasian plate and is being forced upwards. The Caledonian mountains formed at this time and it is thought they were as high as the modern Himalayas when they formed. At the start the Iapetus oceanic crust was subducted beneath continental crust, but eventually the oceanic crust was gone and continents collided. This occurred in Ireland with the closure of the Iapetus Ocean over 450 million years ago. The less dense conitinental crust is forced upward. Oceanic crust is typically denser than continental crust and is forced downwards into the hot mantle when it collides with continental crust. Subduction occurs when there is a difference in the density of the plates. It is possible to have the collision of two oceanic plates, an oceanic plate and a continental plate or two continental plates. The result depends on the type of plates involved. This is when two tectonic plates move toward each other and collide. See volcanoes for more on the effects of divergent plate boundaries (redirect to Topics section).Ĭonvergent or d e s t ruc t iv e pla te boundarie s Antrim, formed at the opening of the North Atlantic approximately 60 million years ago. The Paleogene rocks in Ireland, including at Cooley, Co. It is associated with rifting (large-scale faulting) and volcanoes.Īn example of this is the mid-Atlantic ridge. It happens at the start of a new ocean and continues at the mid-ocean ridge while the ocean is opening. It happens when two tectonic plates pull apart and rock from the mantle rises up through the opening to form new surface rock when it cools. The plates diverge and this causes the construction of new rock.
There are three types of plate boundary:ĭivergent or co n s t ruc t iv e pla te boundarie s The areas where these plates meet are known as plate boundaries. Ireland has a long and interesting tectonic history and therefore, we have a great diversity of rock-types in a relatively small area. The word tectonic refers to the structure of the earth and the processes happening on it. The tectonic plates are in motion and it is thought that they have been in motion since early in earth's history.
Source: USGS, , Public domain, via Wikimedia Commons There are seven major plates that make up 94% of the Earth's surface and many smaller plates making up the other 6%.
The Earth's crust and upper mantle is broken into many plates called tectonic plates that are like pieces of a jigsaw puzzle.
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