GLOBAL TECTONICS - RIGDES

Global tectonics deals/embraces the structures of the earth on big scale and when, very big structures are involved. It is termed Geotectonics (its emphasis to its global effects).

Those geotectonics structures are:

Oceanic Ridges
Oceanic ridges are formed from the tectonic process, where two plates diverged and created an opening, and magma came and filled it up.
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A diver at the mid ocean ridge
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Geo syncline
Geosyncline are large-scale depression on the earth crust, where sediments are deposited. They can be called depocenters.

Wilpena Pound; Flinders Range, Australia [2374x1684]
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Mountain belts
Mountain belt are group of mountain with the same form, same structure, formed from the same orogeny processes.

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Tectonics is concerned with relative movement of part of the earth, it is associated with world as plate.

Features of the earth crust that may be used to define a series of major region of the earth crust.

The earth surface is divided into 6 major plates and other minor ones and the plates are composed of the same materials as the fluid mantle where they underlie the world ocean.

The are super cooled into solid rock estimated to be 10-16km, the thickness varies especially where the plate contains continental materials.
The thickness of oceanic plate is defined by the insulating properties of a frozen mantle, the surface of the plate is maintain at 39°F (temperature of deep ocean). The underside is at the melting point of the mantle material. it is at the temperature of 1100.

The plate are bounded by an interconnected network of inter-boundary types namely.

• Ridges (Today's Focus)

• Trenches

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• Transform faults

Image credit: gettyimage

Each type is associated with different types of seismicity. plate tectonics is a unifying theory of present day movement and its states that The crust and the uppermost mantle of the earth are divided into small number of thin and rigid spherical caps known as plate. They move tangentially with respect to one another perpendicularly, or away from each other.

The material of the plate is the lithosphere which rests on the part of the upper mantle (Aesthenosphere).
The plate boundary is divided into two plates, the region where three plates meet is known as Triple Junction.

Ridges

They are also know as spreading centers, (diverging and constructive), here two plates move away from each other, and as the plate separate hot molten material flow up to fill up the void.

Increase in heat source causes reduction in density with resultant floating of the plate. they tend to occupy the media position in each of the main basin however, the plate boundaries that follows it, is Pacific rise.

They may occur as very broad swell on the seafloor example. East Pacific, they can also occur as sharper features as we see in the mid Atlantic Ridge, they may be associated with local physiographic features arising from faults e.g ridge through the Atlantic Ocean, the ridge along the East Pacific rise is associated with longitudinal block faulting, it is important to know the location of many active volcano with Tholeitic basalt as the principal extrusive rock, they are characterized generally as zone of high heat flow, the earth that occurs are at shallow depths (depth less than 30km).

Seismicity defines the position of measure of short-time displacement across ridges, while magnetic anomaly gives a guide to their long time displacement. if seafloor rocks acquire magnetic polarity when its place at a ridge, the age of the anomaly and its present distance at the present ridge gives an estimate of the spreading.

The theory of sea floor predict that the age of an igneous rock beneath ocean basin increase progressively with distance from a ridge, so long as the material originate with the ridge.

Plate tectonics encompasses sea floor spreading as one of its major part and makes it ideally clear that the seafloor and the lithosphere beneath are created simultaneously at ridges.

The other part of the articles about will be completed in the next posts (Trenches, Transform faults)

References: http://www.newworldencyclopedia.org/entry/Plate_tectonics

https://www.google.com/url?sa=t&source=web&rct=j&url=https://courses.seas.harvard.edu/climate/eli/Courses/EPS281r/Sources/Plate-tectonics/Sea-floor-spreading-and-magnetic-reversals/1_Plate%2520tectonics%2520-%2520Wikipedia,%2520the%2520free%2520encyclopedia.pdf&ved=2ahUKEwjv5a3h35naAhVFuRQKHZgjBOIQFjAAegQIBxAB&usg=AOvVaw2OdScvB8dYbc2ziUL3KX6w
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