Unit 1 Geology

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  • Created by: Benton33
  • Created on: 22-02-14 14:40

The Bowen Reaction Series

Topic 20

100 years ago- Mr Bowen discovered a prediction sequence to how magma changes as it rises, and new minerals are formed under different conditions.

The sequence is split into two seperate branches, continous and discontinous branch.

Discontinous (Olivine melts first)



Ca rich Plegials---Na Rich Plagalius

If there is enough K and water- the upper minerals will form.

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How Magma Changes

Topic 20

1) Magma mixing- When two streams of lava mix and create a different composition

2) Crystal settling-The lava that cools first is denser and falls to bottom. Felsic lava rises to top and cools there.

3) Assimilation-When the propeties of a certian lava is stolen by certian rocks it passes.

4) BRS (Bowen Reaction Series)

5) Partial Melting (Reverse of BRS)- When Melting rock the more felsic materials will metl first.

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Convection Currents

1) Convection currents are suggested to be the reason why plates move.

2) Magma hits the crust and either moves left or right and dragging the plate with it.

3) Cools down against the crust causing it to descend

4) Begins to heat up again, restarting the process as the core heats it up again.

This accounts to 90-95% of plate movement.

The other 5% is Ridge Push and Slab Pull

Ridge push is where gravity lifts the plate when lava pushes up through the crust.

Slab pull is where a subducting plate and it's angle help to drag another plate downwards with it

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Rock Deformation

All rocks should be flat- but they are not. Why? Because of

Plate tectonics (and weathering and erosion)

Plate tectonics cause stress and strain defomration

STRESS- Is the amount of force applied- types of stress (Different,Compression,Tension, Sheer)

STRAIN-Resulting Physical action

ELASTIC DEFORMATION- Changes shape with stress-but it returns to original shape

PLASTIC DEFORMATION-Changes shae but doesn't go back to orginal shape

FRACTURING-Permantly broken



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Plasicalse (White/Cream)


Barite (Borgate)



Hornblende (Amphiblende) Dark black

Augite (Pyroxene) Dark black with white intervals

Olivene- Olive green colour


Halite- Lick test (Tastes of salt)

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Strike and Dip

Topic 14

Strike and Dip are the measurements on a geological map that represent the structure/angle formation of different rocks.

A strike shows you- The orientation in which the rock is going

A dip shows you- the angle in which the rock is pointing

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Igneous Activity

Topic 20

all igneous rocks are derived from lava.

Two types of igneous rock

Intrusive-magma,crystallites, liquids become solids, Crystals are large

Extrusive-Magma receding to the surface of the earth,crystals are small

Volcanic glass- Cools very quickly, no crystals (Obsidian)

Ultra mafic-Less than 45% silica

Mafic-more than 45% silica

Intermediate- 52-64%

Felsic-More than 65%

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Intrusive land forms

Topic 23

Instrusive-(Cools and forms underground- large to medium sized cyrstals) They cool slowly


Three types- Batholiths, Dykes and Sills

Batholiths- Large cyrstals, Dome shaped, 100km, granite it the most common (Viscous)

Dykes- Medium Sized crystals, Disconcordant stuctures (Cuts across bedding) goes along lines of weakness, average of a metre thick.

Sills-Medium sized crystals, concordant structures, usually dolorite. 1-2 metres thick.

How do they get to the surface?

1) Weathering/erosion

2)Plate tectonics

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