Deformation and Metamorphism
1. Explain the difference between load pressure and directed pressure, using diagrams.
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 ...view middle of the document...
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 process of metamorphism. Heat increases with depth and respectively so does the pressure exerted on underlying rocks. Heating a rock makes the atoms in the minerals vibrate and become more mobile. Eventually the minerals break up and produce new minerals.
Fluids: Diffusion occurs through mineral grains but mainly along the boundaries and minute fractures of the rock. Diffusion is the atoms within the rock beginning to slowly move around. Small amounts of pore fluids, mostly water, greatly assist in this transfer of atoms.
Time: Time is the final factor which is necessary for metamorphism to take place. These small scale processes produce remarkable end products if given an enormous period of time to occur.
4. Describe the metamorphic changes resulting from the intrusion of a large igneous batholith.
a) What is this form of metamorphism called?
This is called Thermal metamorphism because it is caused by heat acting as a single metamorphic agent.
b) Use a diagram to show the contact aureole and how different country rocks are affected by the intrusive rock.
BLACK: Granite Intrusion
c) Explain what factors determine the width of the aureole
There are 3 main factors which affect the width of the aureole in thermal metamorphism. The first factor is the size of the igneous body. The second factor is the temperature of the igneous body and the third factor relating to the width of the aureole is the rock it’s intruding into. Heat will travel much quicker through a porous rock such as limestone compared to other rocks.
5. Complete the following block diagrams and identify each structure.
6. Name each geological structure
a) Tilted bedding
b) Graded bedding
c) Plunging fold
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