Instrusive Volcanic Landforms Flashcards
Why do instructive landforms occur
Magma is forced to the surface and only a small amount reaches that level. Most magma is intruded into the crust where it solidifies into a range of features- exposed by later erosion.
What are batholiths
Formed deep below the surface when large masses of magma cools and solidifies.
Large crystals form.
What do batholiths look like
Some shapes and exposed by later erosion
Example of a batholiths
Dartmoor and Isle of Arran
How big can batholiths be
Several hundred kilometres in diameter
Area surrounding a batholith
Altered by heat and pressure from the intrusion to form a metamorphic aureole
How is a laccolith formed
Smaller injections of magma form a lens shape that is intruded between layers of rock. Forced the overlying strata to arch upwards, forming a dome.
Example of a laccolith
Wilson Hills on the Scottish Borders
- forms a small range of hills
What is a dyke
Vertical intrusions with horizontal cooling cracks. They cut across the bedding planes of the rocks into which they have been intruded.
How do dykes often occur
In groups where they are known as dyke swarms
Example of dykes
Found in Scottish islands such as Mull and Skye
What are sills
Horizontal intrusions along the lines of bedding planes- they have vertical cooling cracks
Example of a sill
Great Whin Sill (carries part of Hadrian’s wall) and on Isle of Arran
What are both sills and dykes commonly made of
Dolerite
