VOLCANOES | Last Minute Revision | Leaving Cert Geography

Geography Talks

4 Dec 202227:14

Summary

TLDRThis video explains key geological features formed by volcanic activity, focusing on different types of magma intrusions such as sills, dikes, and batholiths. The speaker illustrates how magma moves horizontally and vertically within rock layers, forming these structures. The Leinster Batholith in Ireland, a significant geological formation, is explored, along with its role in shaping mountain ranges like the Wicklow Mountains. The video also highlights the Antrim-Derry Plateau and its formation through lava flow. The aim is to provide a clear understanding of volcanic landforms and their impact on the landscape.

Takeaways

😀 Sills are horizontal sheets of magma that intrude between layers of sedimentary rock, pushing the layers apart.
😀 Dikes are vertical sheets of magma that cut across rock layers, forcing fractures further apart as they build up.
😀 Batholiths are large plutons of magma that cool slowly beneath the Earth's surface, forming coarse-grained granite.
😀 The Antrim-Derry Plateau, formed 465 million years ago, is a large lava plateau with a featureless landscape, originally covered in chalk.
😀 Lava from volcanic activity on the Antrim-Derry Plateau created distinctive geological formations like the Giants Causeway.
😀 The Leinster Batholith is the largest batholith in Ireland and the UK, occupying 1500 square kilometers of landscape.
😀 Magma intrusion into the surrounding rock of the Leinster Batholith has resulted in metamorphic rock formation like quartzite.
😀 The Leinster Batholith contains five distinct dome formations, created as magma pushed upwards through the crust.
😀 Over time, weathering and erosion exposed dome-shaped features of the Leinster Batholith, like Table Mountain in the Wicklow Mountains.
😀 The Giants Causeway, located in the Antrim-Derry Plateau, is known for its 60,000 basalt columns formed by cooling lava.

Q & A

What is the difference between a sill and a dike in geology?
-A sill is a horizontal flow of magma that spreads between layers of sedimentary rock, while a dike is a vertical flow that cuts across the layers of rock.
How does a sill form?
-A sill forms when magma pushes through the layers of rock and spreads horizontally between them, causing the rock layers to bulge and create a sheet-like feature.
What conditions favor the formation of sills?
-Sills typically form closer to the surface where there is less pressure from overlying rocks, allowing magma to spread horizontally between the layers.
What are batholiths and how do they form?
-Batholiths are large bodies of magma that cool very slowly deep beneath the surface, forming coarse-grained granite. They are typically deeply buried and can cover vast areas.
What is the Antrim-Derry Plateau, and how was it formed?
-The Antrim-Derry Plateau is a vast lava plateau formed about 465 million years ago when volcanic activity occurred due to the splitting of the European and American plates, causing lava to pour out and cover the landscape.
How did the European and American plates contribute to the formation of the Antrim-Derry Plateau?
-The splitting of the European and American plates caused tension in the Earth's crust, leading to the formation of cracks where lava could escape, forming the Antrim-Derry Plateau.
What is the significance of the Giant's Causeway in the context of the Antrim-Derry Plateau?
-The Giant's Causeway is a notable feature of the Antrim-Derry Plateau, formed by the volcanic activity that occurred as lava cooled and formed distinctive basalt columns.
What is the Leinster Batholith and where is it located?
-The Leinster Batholith is the largest pluton in Ireland and the UK, covering about 1,500 square kilometers. It extends from County Dublin to County Kilkenny.
How did the magma from the Leinster Batholith affect the surrounding rocks?
-The magma from the Leinster Batholith applied heat and pressure to the surrounding rocks, causing them to metamorphose into quartzite, a harder and more resistant rock.
What geological features resulted from the exposure of the Leinster Batholith?
-The exposure of the Leinster Batholith, through weathering and erosion over millions of years, led to the formation of dome-shaped mountains such as Table Mountain in the Wicklow Mountains.