The formation of features on the Earth are derive from the Plate Tectonics Theory
The Plate Techtonics Theory
In the 1950s and later, geophysical evidence from palaeomagnetic and
ocean floor studies led to the synthesis of ideas in plate tectonics. The theory of plate
tectonics modifies the old idea of continental drift, and describes the EARTH as a
restless planet with plates drifting across the surface. The theory is accepted by most
earth scientists today as the modern, more satisfactory explanation of the internal forces
shaping the earth, crustal movements and volcanic activity, formation of major landforms,
and occurence of some major natural disaster.
This theory suggest that the EARTH's crust is made up of seven large slabs or major
crustal plates and seven minor ones. Each plate is made up of rigid continental crust or
oceanic crust with its base extending to the upper mantle.
Continental plates includes:-
- North American plate
- South American plate
- African plate
- Eurasian plate
- Australian-Indian plate
- Antarctic plate
Oceanic plate lies beneath the oceans:-
- Pacific plate
- Nazca plate (Minor plate)
CAUSES OF PLATE MOVEMENT AND INSTABILITY
Plate movement are believed to be caused by complex conventional currents of magma in the
upper mantle (asthenosphere). These conventional currents, driven by heat energy released
by radioactivity (radioactive decay) in the mantle, drag and move the plates above them.
Such movements are irregular and not constant through time. Conventional magma movements
cause plates to move in three different ways:-
- Plates split and move apart in some areas, allowing new crustal material (magma) to rise to the ocean floor from the mantle beneath and form long, high submarine ridges (called the mid-oceanic ridges).
- Plates collide or one plate may slip beneath the another, causing fold mountains and volcanos to form on the land surface, and long narrow oceanic trenches to form beneath the ocean.
- Plates scrape and slide past another, causing faulting and earthquakes.
These movements cause changes (called tectonic processes) and instabilty along plate
boundaries
are unstable zones in the crust.