Big Bang Theory and Plate Tectonics: Key Concepts
The Big Bang Theory
The Big Bang Theory was proposed by the Belgian astronomer Georges Lemaître in 1927 and developed by Russian-born American physicist Georges Gamow in 1948. It posits that the universe was created from a singular event, the Big Bang, as follows:
- Initially, all energy, matter, and space were concentrated in a single point, called the primeval atom, characterized by extremely high density and temperature.
- This primeval atom expanded rapidly in a Big Bang, initiating the expansion of the universe. Energy dispersed in all directions and transformed into matter. Simultaneously, space and time originated.
- Subatomic particles were generated, followed by the simplest atoms: hydrogen and helium.
- As the universe expanded, the temperature decreased. The energy scattered in all directions condensed, leading to the formation of astronomical structures.
Plate Tectonics
Around 1960, the theory of plate tectonics began to develop, supported by accumulating evidence.
What is Plate Tectonics?
- The Earth’s surface is divided into a series of fragments called rigid lithospheric plates, resembling a puzzle.
- These lithospheric plates are not static but change slowly and steadily in size, shape, and position.
- This movement produces significant lithospheric dynamics and friction between the plates, triggering various geological processes and influencing external phenomena.
The Edges of the Plates
1. Convergent Boundaries
Convergent boundaries are the edges where two plates collide.
These boundaries form where two plates approach and push against each other.
In most cases, one plate is forced under the other, sinking into the mantle and melting. This process destroys lithosphere, resulting in a decrease in plate size. Therefore, these areas are called destructive margins.
Collisions between plates can lead to the formation of mountain ranges or orogens.
Destructive margins are the sites of most of the Earth’s volcanoes and earthquakes.
Types of Convergence:
- Convergence between two oceanic lithospheric plates: The older plate, having cooled for a longer period, is denser and more easily subducts into the underlying mantle at a steep angle, forming island arcs.
- Convergence between an oceanic lithospheric plate and a continental lithospheric plate: The denser oceanic lithosphere is forced under the continental lithosphere, deforming it and generating a mountain chain parallel to the convergent edge.
- Convergence between two continental lithospheric plates: Once any oceanic lithosphere between them has been subducted, the consolidation of the two continental plates occurs. Due to its low density, neither plate can fully enter the mantle, resulting in uplift and deformation.
2. Divergent Boundaries
Divergent boundaries are the edges where two plates are moving apart.
The movement of plates away from each other creates fractures that are continuously filled by molten rock from the upper mantle. When this material reaches the surface, it cools, solidifies, and forms new lithosphere. These edges are also called constructive margins because new lithosphere is created.
These areas are characterized by intense volcanism and less intense earthquakes.
The Origin of the Oceans:
- When divergent boundaries form within a continent, they create rift valleys.
- If the rifting continues and connects to an ocean, it floods the valley, creating a sea.
- The seafloor will have a mid-ocean ridge where new lithosphere is created, accompanied by intense volcanism.