Tectonic Plates and the Formation of the Universe and Solar System
Tectonic Plate Boundaries and Their Effects
Destructive Margins (Convergent Boundaries)
Destructive plate boundaries, or convergent boundaries, are areas where volcanic activity produces new oceanic lithosphere. These areas of lithosphere creation are called constructive margins. At these ridges, huge fracture zones exist where basaltic magma exits under pressure. These zones are often patchy and unstable. As the extension of the seafloor originates from each zone, a contraction occurs when two sections of the ridge are separated. If this occurs, a fault zone is produced where shear movement is present. This area is a transform fault.
Convergence Between Oceanic and Continental Lithosphere
Subduction can also begin under the edge of a continental plate. It is characterized by the underlying plate subducting at an angle underneath the mantle. This subduction leads to magmatism and volcanism, which produces the intrusion of granitic rocks into the overlying plate. An arc of islands or other reliefs may be torn from fragments of oceanic lithosphere that end up riding on the continental lithosphere. This process is called obduction. The lithosphere fragments that appear riding on a continent are called ophiolites. There is a lot of pressure on the overriding plate, so subducted sediments do not easily develop an extensive accretionary prism if the trench is shallow. This accretionary prism is highly compressed, and materials are folded in the vicinity of the continental plate. Seismicity is very high in this area, making it the world’s largest seismic risk zone. There is a thickening of the continental plate that leads to orogeny, or mountain formation, on the edge of the continent.
Convergence Between Two Continental Plates
When the oceanic lithosphere between two continents has completely subducted, the continents collide with each other. As the lithosphere is too light to subduct into the mantle, subduction is interrupted after the continental collision. The oceanic plate continues to subduct into the mantle while the two continental lithospheres become embedded and one overrides the other. In the suture between the two plates, an orogen is formed, with an increase in thickness due to the stacking of sediments that had accumulated. Among these sediments, ophiolites can be found from the obduction of oceanic lithosphere fragments that existed between both plates before they collided. The rupture of the continental lithosphere during collisions can lead to the formation of faults and seismicity far from the suture zone. This is the origin of earthquakes in India and Asia. In the suture zone, compression and friction between the plates produce deformation and metamorphic rocks. The fusion of the continental crust can also occur, leading to the formation of granitic rocks.
Horizontal Plate Movements
Three types of displacement can be established based on the edges of the plates:
- Divergent: Occurs when two plates are separating, happening at constructive edges.
- Convergent: Occurs when two plates are closing in, happening at destructive edges.
- Shear: Occurs at passive edges, which are found in transform faults.
Rifting in the Peninsula
The peninsula is subjected to a general uplift that can be observed both on the coast and inland, where river terraces and raised erosional plains indicate that drainage basins are fitted to ascend to the plains. A clear trend towards fracturing can also be seen. The main valleys are formed by rivers circulating along fault scarps, which are often visible.
Origin of the Universe
The universe originated approximately 15 billion years ago in an event that has been named the Big Bang. This event was not merely an explosion of matter into space but the origin of time and space itself, within which electromagnetic radiation and matter composed of particles such as electrons, protons, and neutrons were formed. As space expands, driven by the initial explosion and an expansive force called dark energy, the universe cools.
Star Formation
As a result of expansion, the universe has been cooling. Hydrogen and helium atoms formed in the first moments were bound together, comparable to the condensation of a vapor to form a liquid, and freezing, which leads to a solid state. Thus, gas clouds began to form. These gas masses contracted and reheated inside until thermonuclear reactions began to occur, causing them to shine. That was the birth of the first generation of stars, formed approximately 650 million years ago. The energy produced in these reactions tends to make the star explode, while its enormous gravity compresses it. Thus, an equilibrium is established, and the star keeps shining with a constant size. However, the exhaustion of hydrogen causes the star to decrease in temperature and yield to the pressure of its own weight. It collapses under its gravitational pull, and matter is attracted to its core. A cold, dense core remains, while part of the star’s mass leaves into space, turning into a dust cloud, a nebula, containing all the chemical elements formed in the star. The nebulae seen with telescopes are the result of the explosion of stars that exhausted the hydrogen that kept their thermonuclear reactions shining. These nebulae are formed by dust and expanding gases as a result of the explosion.
Solar System Formation
An expansive gas cloud was slowing down. It contracted and expanded, triggering a chain of processes. The random motion of gas and dust particles was organized as a rotational movement. As it rotated, it flattened at the poles, transforming into a disk. At this stage, its diameter was hundreds of millions of astronomical units, but its thickness could be as little as a few dozen. This is what caused all the components of the solar system to be confined to the plane of the ecliptic. Most of the material in the solar nebula contracted and concentrated in the center, forming a mass that originated the Sun, while the rest of the material agglomerated. Rocky bodies collided with each other, and larger dust particles formed meteoroids. These formed asteroids, minor planets, and planets. The central mass of gas and dust increased its temperature so much that nuclear fusion reactions began within it, and the Sun began to shine. Upon the Sun’s ignition, a cloud of comets called the Oort cloud formed. Only the planets farthest from the Sun retained their gaseous atmospheres. The closest ones became rocky bodies.