Global distribution of fold mountains

Fold mountains in Munster

Folding is when 2 continental plates collide, neither one is less dense so they do not subduct, and are uplifted instead. When rocks are under compressional pressure due to plate tectonics, Fold Mountains occur e.g. the Andes.

Fold mountains in Ireland can be found in the Valley Province of Munster and

Carrauntoohil.

The geological make of the mountain in Munster occurred when all the rivers ran south and brought sands, sills and other sediments and as they built up they became the sandstone we see today.

The Mountains were formed during the Armorican mountain building period in a process called orogeny.

Folding caused a big impact on Muster's landscape and because the pressure was coming from the south, we now see that the mountains have an East-West trend.

Macgillycuddy's Ridge

350 million years ago Ireland was under tropical sea and lay close to the equator.

Due to lithification (compaction and cementation) processes, a layer of carboniferous limestone covered the sandstone in the old red sandstone area.

Because limestone is a soft rock and therefore easily eroded we can see

the sandstone anticlines in places such as Macgillycuddy Ridge. In other places the sandstone actually

protected the limestone and in the Blackwater Valley you can see mounds of limestone synclines. This is like a wave of limestone at the base and sandstone at the tips.

Faulting

When 2 plates start to move away from each other, cracks start to form in the crust, these are called faults. Faulting occurs where there is a weakness in the rocks strata

The African rift valley

A landform created by faulting is a rift valley or graben e.g. East African Rift valley.

Rift valleys occur due to tensional pressure that weaken the crust. When movement continues there more and more faults are formed.

When these are parallel the land between can do one of two things; be uplifted or sink down. A flat valley floor is formed when the land between the faults sink down. The valley has steep escarpments marking the place where the faults occurred.

The East African Rift Valley was formed when the Caribbean and the Naza plate were pulling apart from one another because of a hotspot underneath the plate boundary.

The African Rift Valley has had a big impact on the landscape, this is because it is up to 100 km wide in some places and runs from Ethiopia to Mozambique.