The Earth’s crust and upper mantle is broken into many plates called tectonic plates that are like pieces of a jigsaw puzzle. There are seven major plates that make up 94% of the Earth’s surface and many smaller plates making up the other 6%.
The tectonic plates are in motion and it is thought that they have been in motion since early in earth’s history. The word tectonic refers to the structure of the earth and the processes happening on it. Ireland has a long and interesting tectonic history and therefore,we have a great diversity of rock-types in a relatively small area.
The areas where these plates meet are know as plate boundaries. There are three types of plates boundary:
Divergent or constructive plate boundaries
The plate diverge and this causes the construction of new rock.
It happens when two tectonic plates pull apart and rock from the mantle rises up through the opening to from new surface rock when it cools. It happens at the start of a new ocean and continues at the mid-ocean ridge while the ocean is opening. It is associated with rifting ( large scale faulting ) and volcanoes.
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. They are continually growing at an average rate 1 cm per year ,this will be 10 km I 1 million years.
Also, tectonic plates movements cause earthquakes, tsunamis, and provoke volcanoes eruption.
Passive plate boundaries
Also know as strike-slip or transform boundaries. This is when two plates slide past each other. When the plates move, the jagged edges of the plate boundaries snag and catch each other and can get jammed. This causes a built -up of pressure. When the plates eventually pass each other, the pressure is released in the form of an earthquake. The closest passive plate boundary to Ireland is the boundary between the African and Eurasian plate south of Portugal.
The movement of the two plates can be in opposite directions or in the same direction but at different speeds for example the San Andreas Fault in California.