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Formation of the Earth and Plate Movements

In cosmic science, it's believed that planets formed about 13.8 billion years ago through the Big Bang theory. This theory describes a massive explosion that suddenly brought the universe into existence and caused it to expand rapidly. Initially, the universe was incredibly dense and hot, condensed into a point so small it could be considered a single dot, where matter and energy were intensely concentrated.

According to the Big Bang model, the universe began to expand from this singularity about 13.8 billion years ago. The term "Big Bang" is often used to describe this phase, which is akin to the birth of the universe. The gas and dust scattered by the Big Bang eventually coalesced to form Earth.

Earth formed approximately 4.5 billion years ago from the collapse of a gas and dust cloud in the Solar System. At that time, Earth was within a disk-shaped cloud, with the Sun forming at the center of this disk. Smaller objects forming outside the disk gradually grew and formed the planets of the Solar System.

In the early 20th century, Clair Patterson first calculated Earth's age to be about 4.40 billion years, based on the amount of uranium in zircon crystals. A 2016 calculation indicated that Earth's core is about 2.49 years younger than its surface.

Based on extensive and comprehensive scientific evidence, geologists have determined that Earth is approximately 4.54 billion years old (4.54×10^9 years). This estimation is derived from the age of the oldest known Earth crust minerals (small zircon crystals in Western Australia's Jack Hills) and the age of the Solar System, determined through radiometric dating of meteorite particles and lunar samples.

The Theory of Continental Drift was proposed in 1912 by the German meteorologist Alfred Wegener. It suggests that continents are in motion and have reached their current positions through this movement. Continental drift refers to the large-scale horizontal movements of continents relative to each other and to ocean basins.

Wegener attributed this movement to convection currents in Earth's mantle, a hot, fluid layer inside the planet. These convection currents are caused by the movement of warmer and cooler parts of the mantle relative to each other.

Today, the theory of continental drift is one of the fundamental theories in the field of geology, helping us understand Earth's formation, development, and geological structure.

Plate movements are a geological process where the lithosphere (the outermost layer of Earth's crust and upper mantle) is in constant motion, driven by convection currents in the mantle. These currents arise from the movement of hotter and cooler parts of the mantle. Hot mantle material rises due to being less dense, while cooler material sinks because it is denser. These movements cause the plates to move towards or away from each other.

Plate movements lead to various geological formations on Earth's surface, including mountains, volcanoes, earthquakes, and ocean trenches. There are three main types of plate movements:

  1. Divergent (Spreading) Plate Boundaries: Adjacent plates move apart, creating space that is filled by hot, partly molten magma rising from the asthenosphere. The cooling and solidifying magma spreads symmetrically to both sides, adding to the edges of the diverging plates. This process initiates the formation of new ocean basins. Most of today's oceanic crust has formed in this way.

  2. Convergent (Colliding) Plate Boundaries: Two plates move towards each other and collide, with the denser plate subducting beneath the other. This leads to geological phenomena and structures such as subduction, seismic activity, oceanic trenches, magmatic activity, melange and metamorphism, orogeny, and mineral deposits.

  3. Transform (Strike-Slip) Plate Boundaries: Independently moving plates slide past each other. During this process, there is no significant increase or decrease in the size (area) of the plates. Crustal destruction and regeneration do not occur.

This diagram illustrates the dynamic processes of plate tectonics. On the left, we see colliding plates where two oceanic plates converge, forming a mid-ocean ridge and possibly volcanic islands due to the upwelling of magma. In the center, divergent plates are shown; this is where two tectonic plates, continental or oceanic, move away from each other, causing a rift or a mid-ocean ridge to form as magma rises to fill the gap. On the right, we have colliding continental plates, which push against each other to form mountain ranges
Tectonic Plates

Figure 1. Plate Movements.

Throughout Earth's history, plate movements have led to the disappearance and formation of continents over time (Figure 2). The initial solidification of Earth's outer shell marked the beginning of a 4.5-billion-year cycle during which various supercontinents have formed. These supercontinents have attained their present form through the activity of plate movements. The existence of these continents has been established through the study of ancient cratons and shields in stratigraphic formations and through age data. Geological records indicate that, over the last 3 billion years, other supercontinents besides Pangaea have also formed.

This image presents a chronological overview of Earth's geological history, focusing on the supercontinents and their respective eras. At the top, the title "supercontinents and their ages" sets the context for the timeline of major landmasses. Each of the seven circles below represents a supercontinent at different geological times, indicated in billions (GYA) and millions (MYA) of years ago.

Figure 2: Supercontinents throughout Earth's history that have formed and dissipated.

The tectonic plates of the Earth's crust are in constant motion. Colliding plates lead to the merging and separation of continents. Geoscientists predict that a new supercontinent could form in 200 to 300 million years. What might the shape of this future supercontinent be? There are four different scenarios being considered.

1- Pangaea Ultima: According to this scenario, Africa first moves northward and collides with Eurasia, merging with it. Then, the resulting Afro-Eurasian continent collides with the continents of North and South America, closing the Atlantic Ocean. The Pangaea Ultima supercontinent is surrounded by the Pacific Ocean. The formation of Pangaea Ultima is centered on the 0-degree meridian. Another potential future supercontinent could be Novopangaea.

2- Novopangaea: This is thought to form with the closure of the Pacific Ocean. In this scenario, as Antarctica and Australia move northward, the continents of North and South America collide with Asia. Africa forms the northeast of the supercontinent. Novopangaea is centered on the 180-degree meridian, the international date line.

3- Aurica: The formation of the Aurica supercontinent is associated with the closure of both the Atlantic and Pacific oceans, while a new ocean is predicted to form in the region of Asia. In this scenario, Asia fragments along a line extending northward from the Pakistan-India border. Australia and Antarctica move north and collide with East Asia. Meanwhile, as East Asia merges with the continents of North and South America, the Pacific Ocean closes. The collision of the African and European continents with North and South America leads to the closure of the Atlantic Ocean. Aurica is expected to be surrounded by the Asian Ocean. The formation of Aurica is centered on the 180-degree meridian, the international date line.

4- Amasia: Distinct from the other three scenarios, all continents except Antarctica move northward and merge in the Arctic region. During this process, the Arctic Ocean closes. Amasia is predicted to form in 200 million years, centered on the 0-degree meridian.

These predictions provide insights into the potential shapes of future supercontinents. The continual drift of continents in Earth's geological history is a true phenomenon, akin to the ongoing expansion of the Universe.

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