Plate Tectonics

sophisticated models of the dynamics and mechanics of plate tectonic motion and collision enable prediction of future plate tectonic movements and provide data for local evidence-based decision making, for example, development of infrastructure, location of geothermal resources
Earth hazards result from the interactions of Earth systems and can threaten life, health, property, or the environment plate tectonic processes generate earthquakes, volcanic eruptions, and tsunamis. Earth hazards result from the interactions of Earth systems and can threaten life, health, property, or the environment
Catastrophic events can affect other Earth processes, including the influence of volcanic emissions on climate and weather plate tectonic processes generate earthquakes, volcanic eruptions and tsunamis; these events can affect other Earth processes, including the influence of volcanic emissions on climate and weather

Different Types of Plate Boundaries and their Typical Geological Features.

Convergent Boundaries

When two plates collide.

- There are two types collison zones;

Destructive Ocean-continent: type of location for subduction related metamorphism in the cold subducting slab. Thickened continental crust in subduction zones (arcs) with additional heat. Contact zones with arc batholiths and with shallow intrusions, due to magma flux the contacts range through all regional zones.
Destructive Continent-continent: Type location for regional metamorphism, the roots of the mountain belts in thickened crust can reach high grade metamorphic conditions. Typical Barrovian zone metamorphism. Contact zones with batholiths, can be interrelated regional metamorphism often as an overprint on a regional burial trend.

Oceanic-Continental Convergence Summary

Initial point of subduction is indicated by trench.
Intensely folded mountain ranges.
Andesitic volcanism and granitic magma intrusions.
Regional and contact metamorphic rocks.
Shallow to deep focus earthquakes.
The growth of continental crust.

Oceanic-Oceanic Convergence Summary

Initial point of subduction indicated.
Island arch chain.
Andesitic volcanism and granitic magma intrusions.
Regional and contact metamorphic rocks.
Shallow to deep focus earthquakes.

Continental-Continental Convergence Summary

Inensely folded mountains.
Regional Metamorphism.
Shallow to medium focus earthquakes.
Usually no subduction, volcanoes or magma intrusions.
No trenches or contact metamorphism.

Divergence Boundaries

Divergent boundaries are spreading centres where new crust is generated.

Constructive Zones Mid Ocean Ridge.

Hydrothermal metamorphism, thermal convection cells of sea water can cause widespread hydrothermal alteration of the oceanic crust.
Contact metamorphism within local contact zones with shallow intrusions, may overprint or predate hydrothermal.

Oceanic-Continental Convergence Summary

Youngest rocks found at the divergent boundary and get progressively older the further they are from it.
Fissure eruptions typical, with basaltic rocks formed as a result.
Boundary characterised by an elevated rift valley.
Little to no metamorphism.
Shallow focus earthquakes only.

Transform Boundaries

Passive/conservative boundaries since no new crust forms and no old crust is destroyed.

No volcanism.
Shallow focus earthquakes.
Opposite and parallel plate movement on either side of the boundary.

How Do Plates Move?

The plates are driven across the outer surface of the Earth by huge convection currents in the mantle.
The convection is facilitated by the physical differences in the crust and mantle, and the unequal heat distribution produced by radioactive decay of elements suck as K, Th U and residual heat from Earth's formation.
At convergent boundaries creating descending arms of convection currents.
Divergence boundaries allow heat to escape from Earth's interior vis rising mantle material.
Subduction plates also drag a lot of seawater back into the mantle.
Although convection currents play a role, two forces ridge-push and Slab-pull influence each plate's movements.
Seismic tomography reveals descending slabs can remain coherent in some cases down to the core-mantle boundary and suggests that interactions there may generate mantle plumes.
Plates with the greatest length of subducting slab attached travel fastest, indication the significance of this force in driving plate motion.

Convection Currents

Ridge-push

Is a mechanism that drives the motion of tectonic plates at mid-ocean ridges.
As new crust is formed at the ridges through volcanic activity, it is elevated and pushes the adjacent plates away from the ridge.
The force generated by the elevated ridge acts as a pushing force, causing the plates to move away from the ridge.

Slab-pull

Refers to the gravitational force that drives the motion of tectonic plates at subduction zones. When a denser oceanic plate sinks beneath a less dense continental plate or another oceanic plate, it is pulled downward by gravity into the Earth's mantle.
This sinking motion generates a pulling force on the rest of the plate, causing it to move towards the subduction zone.

How fast Do Plates Move?

The speed at which tectonic plates move can vary, but on average, they move at a rate of a few centimeters per year. The movement of plates is a slow process that occurs over long periods of time. The speed of plate motion is typically measured and described in terms of centimeters per year or millimeters per year.

For example, the rate of movement along the Pacific Plate's boundary with the North American Plate, which includes the San Andreas Fault in California, is estimated to be around 5 to 10 centimeters per year. The rate of the African Plate's movement is estimated to be about 2 to 3 centimeters per year.

It's important to note that plate motion is not uniform across the entire plate boundary. Different parts of a plate boundary can have different rates of movement. Additionally, plate motion can change over time due to various factors, including the interactions between different plates and the geological forces acting on them.

To determine the speed of plate movement, scientists use various techniques such as GPS (Global Positioning System) measurements, satellite data, and geodetic surveys. These methods allow them to track the relative movement of different points on the Earth's surface and estimate the rate at which tectonic plates are moving

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