Tectónica de placas y deriva continental

Plate Tectonics

Earth is divided into multiple plates that move around the planet. These plates make up the Earth's crust, which can be broken down into two main types: oceanic and continental. Although these major types of crust may appear similar under a microscope, they have significant differences. Oceanic crust, also known as basaltic crust, is denser, thinner, and more mafic (richer in iron) compared to continental crust. Conversely, continental crust has lower density due to its lighter silicium composition and forms a thicker layer over the core mantle boundary.

Plates make up 10% of the Earth's volume but contain 75% of the mass because they are denser. There are no specific minerals that uniquely characterize either type of crust; however, temperature and pressure are important factors determining their densities.

The movement of these plates leads to the formation of plate boundaries where plates either collide, are separated, or slip along each other. These events create volcanic activity, earthquakes, and mountain building processes. The movement of these plates can also cause changes in regional landscapes over time, leading to phenomena like continental drift, which is the slow movement of large landmasses across the Earth's surface due to the shifting of the tectonic plates underneath them.

Plate Boundaries

There are three types of plate boundaries: convergent, divergent, and transform (sliding):

• Convergent plate boundaries occur when two plates come together. One plate may slide under another (subduction) or move above another in an oceanic-continental collision (collision boundary), causing the creation of volcanic arcs or active fault lines. Subduction zones include trenches that form as water-rich sedimentary rocks become denser than surrounding oceanic crust and sink into the mantle.

• Divergent plate boundaries, also known as spreading centers, happen when plates separate from each other. This process creates new seafloor in mid-ocean ridges. In some cases, magma intruded from below forces apart the edges of the plates, allowing magma to rise through the gap between the plates.

• Transform plate boundaries occur when the plates slide past each other without any fusion, producing synclinal folds and anticlinal folds that result in mountains such as the Rockies and the Appalachians. Examples of this type of plate boundary include strike-slip faults and the San Andreas Fault.

Continental Drift

While people often associate plate motions with earthquakes and volcanism, it is less well appreciated that these forces also drive major movements among continents and oceans. Like pieces on a moving conveyor belt, the world's continents have been sliding around the planet for billions of years, slowly rearranging their positions.

One example of this phenomenon is the separation of South America and Africa approximately 180 million years ago, which allowed Atlantic Ocean basins to form. Another instance involves the collision of India with Asia about 50 million years ago, which created the Himalayas.

Continental drift occurs due to the powerful convective currents deep within the hot interior of our planet. As the continent moves, its geological makeup is altered by these internal forces, resulting in various geographical features we see today.