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UNIT 10 (The Wilson cycle (3: Formation of an ocean in expansion. The…
UNIT 10
The Wilson cycle
3: Formation of an ocean in expansion. The valley formed between the incortinental rift floods and keeps separating, a ridge develops and the oceanic lithosphere expands between the two continental boundaries.
4: Ocean reduction. In areas far from the ridge and close to the edge of the continent, the ocean lithosphere breaks up and subducts. As it sinks into the mantle, this lithospheric mass pulls on the plate, forming a convergent boundariy that reduces the seabed.
2: Rift formation: The fractured continental lithosphere sinks and creates an intercontinental lift.
5: Continental collision. When the oceanic lithosphere is fully subducted, the ocean closes up, the two continents collide, and the rocks fold forming a mountain range.
1: Continental fragemantation. The dynamics of the plates creates tension that can cause continental mass to fracture along an axis and the two resulting parts begin to separate.
Magmatism
Volcanic activity
This widens the cracks creating a colcanic pipe and a crater at the top. That release of magma is known as a volcanic eruption.
The magma accumulates in the magma chamber before the volcano is formed. When the cracks appear in the crust, the pressure is reduced and the magma is suddenly released.
Occurs when magma occurs when magma that rises through the lithospere pours out onto the surface through an opening in the crust known as a volcano.
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Plutonic activity
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Is the rise of magma through rocks in the lithosphere which later setts, cools and solidifies inside the crust.
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Ignoeus rocks
Plutonic
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Granite, diotite, gabbro...
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Volcanic
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Riolite, obsidian, basalt...
Metamorphism
They can be caused by an increased in temperature, an increased in pressure or water contaning dissolved substances infiltrating the rock.
Where it occurs
At ridges, where the magma generated under the rift increases the temperature of the rocks.
At transform boundaries, where friction between plates causes pressure and temperature to increase.
At convergent boundaries, where the plates pushing together increases the pressure and the magma generated by the subducting plate increases the temperature.
In areas inside the plates, where metamorphism is produced in rocks near hotspots or areas where thick sediments accumulates, increasing the pressure of the rocks underneath.
Is a set of endogenous geological processes whereby factors such us temperature and pressure transform existing rocks into metamorphic rocks without meliting them.
Effects
Temperature and the water containing dissolved substances cause chemical reactions in the minerals of the rock. This can produce an increase in the size of the crystals or the appearence of new minerals.
The pressure squash the mineral crystals and arranges them into sheets facing a single direction. This appearence is knwon as foliation.
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Geological processes
They are the processes which cause the changes that take place in the lithosphere as a rssult of interaction between plates.
Types
Endogenous: They are those that originate inside the Earth as a result of forces or changes in temperature.
Exogenous: They are those that originate in the lithosphere as a result of changes in the geological environment.