Deformation and Metamorphism

Deformation and Metamorphism
  1. Explain the difference between load pressure and directed pressure, using diagrams.

Directed Pressure
Load Pressure

Load pressure refers to when underlying rock has equal pressure exerted on it from all sides. However, directed pressure is when there is not equal forces pressing on the rock from all directions and lateral forces which cause compression and buckling of rocks.
  a) What observable differences are there between rocks affected by load pressure and directed pressure?
Texture, size and shape are all things which change when a rock is subjected to directed pressure. Directed pressure caused grains to become distorted and then recrystallise to finer grained granular aggregates. A rock which has been subjected to directed pressure is also likely to be elongated into a different shape.
  b) Describe three textures that result from directed pressure
Slaty Cleavage is foliation in very fine-grained rocks which results from directed pressure and the parallel alignment of microscopic mica flakes. This property is what causes the rock to be easily split apart.
Lineation is also caused by directed pressure to rocks. This texture results from the parallelism of prismatic minerals and is why it resembles a bunch of pencils.
Layering is another metamorphic structure which might result from directed pressure. Instead of the minerals being evenly distributed throughout the rock; certain minerals are concentrated in layers. This structure is common in rocks called gneiss and is called a gneiss structure.

  2. Explain with diagrams the difference between a horst and a graben.

A Graben is a long, narrow trough which is bounded by one or more parallel normal faults. A horst is the opposite; it is a ridge which is most commonly caused my normal parallel faults.

  3. Name and discuss the four main factors which cause metamorphism
Heat and Pressure: Heat and pressure work simultaneously to begin the...