Placas Tectónicas: ¿Que son las Placas (litosféricas) tectónicas?
Earth's Structure and Plate Tectonics
The video discusses the structure of the Earth, focusing on the lithosphere, mantle, and plate tectonics.
Earth's Layers
- The Earth's rigid outer layer is called the lithosphere, which breaks into massive plates. These plates move continuously through processes like plate tectonics.
Mantle Composition
- The mantle is a rocky layer high in magnesium silicate with a thickness of 2,900 kilometers. It lies between the crust and core.
- The upper mantle (lithosphere) is colder and more rigid than the deeper mantle.
- A hotter and ductile layer beneath is called asthenosphere.
- Analogy: Rocks can be brittle or ductile like a candy bar – brittle when cold and ductile when hot.
Plate Composition
- Plates consist of a crust above the stiffer part of the mantle. Despite different compositions and densities, these layers move together as one mechanical layer known as lithosphere or tectonic plate.
- Earthquakes occur at brittle plate boundaries where rocks fracture due to stress.
- Continental plates are thicker (150-200 km) than oceanic plates (50-140 km).
- Oceanic crust is denser due to less silica but more iron and magnesium.
- Forms ocean floors below sea level while continental crust forms continents above sea level rich in granite, sedimentary, and metamorphic rocks.
Plate Movements
- Relative plate movements fall into three main categories: transform faults, divergent boundaries, and convergent boundaries.
- Transform faults involve horizontal movement between plates sliding past each other.
- Divergent boundaries occur where plates move apart forming new oceanic crust from melted mantle material at mid-ocean ridges.
- Convergent boundaries see plates collide; subduction zones form when an oceanic plate descends beneath a continental plate causing earthquakes and volcanic activity.
- Mountain ranges result from continental collisions lifting landmasses horizontally during convergence events.