The plate tectonic theory

Plates

The Earth’s rigid outer surface or lithosphere consists of seven large and numerous smaller segments called plates.

Tectonic Plate Theory

- Explains the mechanism of movement of tectonic plates. Like continental drift, it suggested the existence of a supercontinent like Pangaea.

Plate Boundaries

A plate boundary is a fracture separating one plate from another. All major interactions among individual plates occur along their boundaries.

Different types of plate boundaries

There are three types of Convergent plate Boundaries

Oceanic-continental convergence

Oceanic-continental convergence forms trenches, destructive earthquakes, and rapid uplift of mountain ranges, as well as the building of volcanic arcs, such as the Cascades of the United States and Andes Mountains of South America.

Continental-continental convergence

Continental-continental convergence forms mountain ranges, such as the Himalayan Range and the European Alps.

Oceanic-Oceanic Convergence

- Oceanic-Oceanic convergence also forms trenches, such as the Mariana Islands between the Philippine Sea Plate and the Mariana Plate, the Aleutian Islands between the Pacific Plate and North American Plate, and the islands of Japan.

Divergent Plate Boundary (Constructive Margin)

- At the divergent boundary, also known as the spreading center or rift zone, two plates move apart. As the plates move away, the fractures that are formed are filled with hot magma via upwelling.
- The mechanism of creating new seafloor along the oceanic ridge system is called seafloor spreading.

- A divergent plate boundary can also split apart continental crusts. The process is called continental rifting.

Transform Plate Boundary (Conservative Margin)

A transform plate boundary forms when plates slide horizontally past one another, Conservative plate margins commonly affect active spreading ridges, producing zigzag plate margins.

The Philippine archipelago is formed through the convergence of the Philippine Sea Plate, the Eurasian Plate, and the Indo-Australian Plate.
The Philippine Mobile Belt (PMB) is the zone of intense deformation and active seismicity between convergent zones bounding the Philippine archipelago.

Evolution and characteristics of the Ocean Basin

Ocean Basin

An oceanic basin is anywhere on Earth that is covered by seawater.

Continental Shelf

relatively shallow, gently sloping part of continental crust that borders the continent.

Continental Slope

The region of the ocean that leads to deep water.

Continental Rise

It links the deep ocean basin floor to the continental slope.

Topographic Features of the Oceanic Basins

Ocean ridges or Mid-ocean ridges - are underwater mountain ranges that consist of newly-formed basaltic rocks.

Trenches - These are long, narrow creases in the seafloor that form the deepest part of the ocean.

Abyssal Plains - are relatively flat, underwater plains covered by sediments, lying between the foot of a continental rise and a mid-ocean ridge.

Guyots - are flat-topped seamounts that are subsided below sea level through millions of years of weathering, mass wasting, and wave action.

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