Geology

GEOLOGY
The western and south western areas of Erris contain some of the oldest rocks in the country. At Annagh Head there are gneisses which are 2000 million years old, the oldest recorded to date in Ireland. The similarity of the rock type and structure of the Mullet Peninsula with that of the eastern seaboard of North America namely Newfoundland and Greenland, has led geologists to conclude that these areas were once joined together and were subsequently torn apart when the Atlantic began to open up 200 million years ago.

The Inishkea Division:
The majority of rocks in Erris belong to what is called the Dalradian Supergroup. These metamorphic rocks which consist mainly of schists, are found in the Inishkea Division, and are mainly present in the south-western areas of Erris. These schists were formed from the deposition of eroded material into the borders of Continental shelves and Oceanic trenches. The deposition is believed to have occurred between 650 and 950 million years ago.

GÉOLAIOCHT
Is in iarthar agus in iar-thuaisceart Iorrais atá cuid de na carraigeacha is sine sa tír le fáil. Tá naghasanna ag Ceann Eanach atá 2000 milliún bhlain d’aois. Tá gaol idir an cineál carraige atá le fáil ar Leithinis an Mhuirthead agus na carraigeacha atá le fáil ar chósta thoir Meiriceá Thuaidh, go h-áirithe i d’Talamh an Éisc agus sa Ghraonlainn. Mar gheall ar seo creideann na géolaí go raibh an dá áit greamaithe le chéile, sular oscail an t-Aigeán Atlantach suas, 200 milliún bliain ó shin agus scar sé óna chéile iad.

Roinnt Inish Geidhe:
Ta baint ag formhór na gcarraigeacha in Iorrais leis an ‘Sárghúpa Dalriadach’. Tá na carraigeacha meiteamorfacha seo, gur siostaí iad den chuid is mó, le fáil i Roinnt Inish Geidhe, agus is in iar-dheisceart Iorrais is mó atá siad le fáil. Cruthaíodh na siostaí seo nuair a leagadh síos ábhar creimithe i dteorainn na scairbheacha ilchríochacha agus na dtrinsi aigéin. Tá na géolaí den tuairim gur tharla sé seo idir 650 agus 950 milliún bliain ó shin.