Understanding Oceanic and Continental Crust Dynamics
A Structured Soil Layers: Differences in Geochemical Units: refer to the Chemical Composition of the materials that compose them. Certainty: The outer layer extends to the Moho discontinuity. The most abundant chemical elements are: O, Si, Al. Continental Certainty: ranges from 25 to 70 km thick. The bottom half is dominated by metamorphic rocks, while the surface consists of Sedimentary Rocks. Ocean Certainty: is much thinner, between 5 and 10 km. It consists of three levels: Layer of Sediments, a Layer of Basalt, and a Gabbro Layer. Its age ranges from 0 to 180 Ma. Mantle: The discontinuities between Mohorovičić and Gutenberg. The most abundant elements in the mantle are: O, Si, Mg, Fe, and it is composed of Peridotite. Core: Its high density ranges between 10 and 13 g/cm³ and is composed of Fe and Ni. Dorsals and Deep Ocean: The ocean ridges in the Atlantic Ocean represent an undersea tour. The ridge is interrupted by transverse fractures. Distribution and Scarcity of Sediments: Sediments are not evenly distributed; their thickness increases as we move away from the ridge. Youth Oceanic Certainty: In the ridges, the basalts are current, formed in the last million years. The Age of the Sediments: Increases as we move away from the ridges, but this age never exceeds 180 million years. Dynamics of the Ocean Floor: The magnetism in rocks is called Paleomagnetism. Its study has revealed that the Earth’s magnetic field has reversed many times.
Theory: It was discovered that the basalts of the oceanic crust show a striking Magnetization in Bands Parallel to the Axis of the Ridge. To explain the magnetic strip, the Theory of Ocean Floor Spreading was developed. This theory can explain the volcanic activity occurring at ridges and the increasing age of the ocean floor as we move away from them. Extension of the Seafloor: Period 1: Magma reaches the dorsal and cools to form crystals. Period 2: The lithosphere moves away to one side, and the space left is occupied by new magma. Period 3: The process of creating new oceanic lithosphere continues, with basalts recording the existing magnetic field. Why Does the Ocean Floor Sink? As the lithosphere moves away from the ridge, it becomes denser, causing it to sink. This collapse is called Thermal Subsidence and explains why the ocean floor is deeper than these areas. Subduction is the process by which the lithosphere is introduced into the interior of the land. It does not inevitably occur when it reaches 100 Ma but can be delayed until it is 160 or 180 Ma. Subduction Zones: Also called Convergent Margins. As a result, oceanic lithosphere is destroyed. There are three cases of convergence: Continental-Oceanic, Oceanic-Oceanic, and Continental-Continental. Convergence Continental-Oceanic: The oceanic plate is inserted below the continental plate. The low melting point of minerals allows for partial melting, producing magmas that feed volcanic eruptions. Convergence Ocean-Ocean: Spontaneous subduction occurs, with the lithosphere penetrating into the mantle at a large tilt angle, resulting in very deep pits without forming an accretionary prism. Convergence Continental-Continental: This occurs when an oceanic plate and a continental section encounter each other. Because the continental lithosphere is less dense, it subducts slightly or not at all during a Collision.