The Bowen Reaction Series
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.
How Magma Changes
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.
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
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
Hornblende (Amphiblende) Dark black
Augite (Pyroxene) Dark black with white intervals
Olivene- Olive green colour
Halite- Lick test (Tastes of salt)
Strike and Dip
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
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
Felsic-More than 65%
Intrusive land forms
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?