The crust is the Earth's coldest layer. There are two parts to it -- the OceanicCrust and the Continental Crust.The Oceanic Crust The Oceanic Crust lies beneath the oceans. It is between 4 to 7 miles (6 - 11km) thick. Its rocks are heavy and young, not more than 200 million years old. They are mostly basalt, which has a gritty volcanic structure.
The continental crust floats much more freely on the magma. Movements deep within the Earth, which carry heat from the hot interior to the cooler surface, cause the plates to move very slowly on the surface, about 1 to 10 cm per year. Tectonic plates move because mantle rocks near the radioactive core are heated and the warmer rocks rise while the cooler
Violent movements of the plates in the Post-Glacial era created the Puerto Rican Trench, nearly 24,000 feet deep, which is the deepest point in the Atlantic Ocean. This trench is also characterized by one of the most negative gravity anomalies on the planet; a force of -380 milliGal is present, which indicates an active downward force in the deeper portions of the water (oceanexplorer.noaa.gov). Puerto Rico’s location near the major tectonic plates is the primary concern for future natural disasters that could change the landscape of the island and cause serious damage to the modern population and infrastructure. “Because the island lies on an active plate boundary, earthquakes are a constant threat, and the densely populated coastal areas are vulnerable to tsunamis. Erosion is a concern in many coastal areas, but is particularly serious to island economies that rely heavily on the tourist industry (oceanexplorer.noaa.gov).” Geological studies of the islands indicate that the western portion of the island has high risk of damaging ground motion, equal to that of Seattle, Washington.
The plates meet with each other, and if rough spots cause the movement to stop at the edges, the motion of the plates continue. When the rough spots can no longer hold, the sudden release of the built-up motion releases, and the sudden movement under the sea floor causes a submarine earthquake. This area of slippage both horizontally and vertically is called the epicenter, and has the highest magnitude, and causes the greatest damage. As with a continental earthquake the severity of the damage is not often caused by the earthquake at the rift zone, but rather by
These are boundaries where the plats move towards each other but 1 plate travels underneath (subduction). The less dense oceanic plate is the plate that subsides under the denser continental plate. The oceanic plate with melt as it falls to the asthenosphere creating a mantle plume where we expect to see a strombolian (cone) volcano. These volcanoes are typically tall cone shaped volcanoes. They are as such because they lava is andesitic/rhyolitic which means the lava contains 55%+ silica content.
Tectonic Plates:- The movement of Continental plates, furthermore renowned as Tectonic Plates, is renowned as “Tectonic Movement”. It is a technical theory that recounts the large-scale movement of Earth's lithosphere i.e. the outer layer of earth. Geologically, the outer layer of earth, which is also renowned as “Crust”, is divided into “lithosphere” and “Asthenosphere”. This is founded on dissimilarities in mechanical properties and in the procedure for the transfer of heat.
These P waves are able to travel through both solid rock, such as granite mountains, and liquid material, such as volcanic magma or the water of the oceans. The slower wave through the body of rock is called the secondary or S wave. As an S wave propagates, it shears the rock sideways at right angles to the direction of travel. If a liquid is sheared sideways or twisted, it will not spring back, hence S waves cannot propagate in the liquid parts of the earth, such as oceans and lakes. The actual speed of P and S seismic waves depends on the density and elastic properties of the rocks and soil through which they pass.
The salinity and temperature of the water influence its density, and the differences in density are the major factor in understanding the formation of currents and the positions of water masses in the sea. In addition, temperature and salinity play major roles in influencing the distribution of plants and animals. The sediments of the sea floor may be divided into lithogenous, hydrogenous, biogenous, and cosmogenous sediments. Lithogenous sediments are the major sediments on the ocean floor. They are derived from the chemical and mechanical weathering of rocks.
Alfred could not explain how the huge masses of land could have moved so far. The major means for the lithospheric plates to float on the asthenosphere comes from the process of convection in the mantle of the Earth. Heat from the outer core rises in the mantle and “melts” the upper part, which is called the asthenosphere. The plates of the lithosphere move in three main ways. There are divergent boundaries where the plates are moving away from each other and new land is formed as magma is released from inside the mantle.
A sedimentary rock is a rock made out of sediments that compacted and cemented together. Metamorphic rock is the result of rocks that have gone through heat and pressure. Three common metamorphic rocks are schist, marble, and gneiss. Metamorphic rocks are denser than most rocks. Temperature can heavily effect how a metamorphic rock changes.