Plate Tectonics By Suzan Alkohaif Oceanic Crust vs

Plate Tectonics By Suzan Alkohaif

Oceanic Crust vs Continental Crust Oceanic Crust • • the relatively thin part of the earth's crust that underlies the ocean basins. It is geologically young compared with the continental crust and consists of basaltic rock overlain by sediments. Oceanic crust is about 6 km (4 miles) thick. It is composed of several layers, not including the overlying sediment. The topmost layer, about 500 meters (1, 650 feet) thick, includes lavas made of basalt (that is, rock material consisting largely of Continental Crust • • the relatively thick part of the earth's crust that forms the large landmasses. It is generally older and more complex than the oceanic crust. Continental crust is the crust under which the continents are built and is 10 -70 km thick, while oceanic crust is the crust under the oceans, and is only 5 -7 km thick. The deepest mine shaft ever built, called Western Deep in South Africa, currently reaches 3. 9 km, which is tiny compared to the continental crust. Forty percent of the earth's surface is currently covered with continental crust. It's important to note that not all continental crust is above sea level. Some Differences are is that Oceanic Crust is thinner, denser, younger, and of different chemical composition. Like continental crust, however, oceanic crust is destroyed in subduction zones. But Continental Crust Continental crust is part of the Earth’s surface found under land masses, and oceanic crust is the surface found under the ocean floor. Also Examples of such rocks are those in Quebec, Canada which are estimated to be about 4 billion years old.

Oceanic Crust and Continental Crust Oceanic Crust Continental Crust

Lithosphere vs Asthenosphere Asthenosphere Lithosphere • • The rigid outer part of the earth, consisting of the crust and upper mantle. Continental lithosphere has a lower mean density than oceanic lithosphere • • the upper layer of the earth's mantle, below the lithosphere, in which there is relatively low resistance to plastic flow and convection is thought to occur. Heat from deep within Earth is thought to keep the asthenosphere malleable, lubricating the undersides of Earth’s tectonic plates and allowing them to move. Some differences are The lithosphere extends to a depth of about 60 mi (100 km). It is broken into about a dozen separate, rigid blocks, or plates The lithosphere Slow convection currents deep within the mantle, generated by radioactive heating of the interior, are believed to cause the lateral movements of the plates (and the continents that rest on top of them) at a rate of several inches per year. The asthenosphere Rocks are "plastic", meaning that they can flow in response to deformation. Deep in the Earth, hot rocks (above about 1300°C) can flow, whereas cold rocks cannot. Rocks are under severe pressure in Asthenosphere, whereas they face much less pressure in lithosphere.

Lithosphere and Asthenosphere Lithosphere Asthenosphere

Convergent vs Divergent Boundary Convergent Boundary • In plate tectonics, a convergent boundary, also known as a destructive plate boundary (because of subduction), is an actively deforming region where two (or more) tectonic plates or fragments of the lithosphere move toward one another and collide. Divergent Boundary • In plate tectonics, a divergent boundary or divergent plate boundary (also known as a constructive boundary or an extensional boundary) is a linear feature that exists between two tectonic plates that are moving away from each other. A divergent boundary is a fault where the two plates are moving away from each other. First of all, volcanic activity is common in these areas since mantle easily moves to the surface through the thin, fractured rock as it separates. If a continent happens to be a place where a divergent boundary occurs, then the continent will begin to be torn apart as the sides of the plates separate, creating a rift valley. A convergent boundary is a boundary where two separate plates are pushing into each other. crust is being pushed into the earth's interior by colliding plates and being re-melted at the same rate new crust is formed.

Convergent and Divergent boundaries Convergent Boundary Divergent Boundary

Folding vs Faulting Folding • • cover or wrap something in (a soft or flexible material). To bend over or double up so that one part lies on another part. Faulting • • be broken by a fault or faults. A fracture in the continuity of a rock form ation caused by a shifting or dislodging of the earth's crust, in which ad jacent surfaces are displaced relative tone another and parallel to the plane of fractu re. (Folds)Folds are bends in rocks that are due to compressional forces. • Folds are most visible in rocks that layered (also known as sedimentary rocks). • Folds are formed when heat and pressure is applied to the rock (Faults)if the pressure (compression) that is applied to a rock undergoing a fold is greater than the internal strength of the rock, then the rock will fracture. This is how faults are formed. Faults are defined as the displacement of rock that were once connected along a fault line.

Folding and Faulting Folding Faulting

Oceanic Crust vs Oceanic Lithosphere Oceanic Crust • it is thinner, denser, younger, and of different chemical composition. Like continental crust, however, oceanic crust is destroyed in subduction zones. • Oceanic lithosphere consists mainly of mafic crust and ultramafic mantle (peridotite) and is denser than continental lithosphere, for which the mantle is associated with crust made of felsic rocks. Oceanic lithosphere thickens as it ages and moves away from the midocean ridge. Differences: There is only a slight difference between crust and lithosphere. The difference is that the lithosphere is part of the Earth that encompasses both the crust and the mantle below it. The crust is the outermost layer of a planet, usually made up of rocky materials. Lithosphere: The lithosphere is the solid, outer part of the Earth. The lithosphere includes the brittle upper portion of the mantle and the crust, the outermost layers of Earth’s structure. It is bounded by the atmosphere above and the asthenosphere (another part of the upper mantle) below. The lithosphere is the most rigid of Earth’s layers. Although the rocks of the lithosphere are still considered elastic, they are not viscous

Oceanic crust and Oceanic lithosphere Oceanic Crust Oceanic Lithosphere

Faults Normal Fault • A geologic fault in which the hanging wall has moved downward relative to the footwall. Normal faults occur where two blocks of rock are pulled apart, as by tension. Reverse Fault Reverse faults are exactly the opposite of normal faults. If the hanging wall rises relative to the footwall, you have a reverse fault. Reverse faults occur in areas undergoing compression (squishing). Differences: Dip-slip faults can be again classified into the types "reverse" and "normal". A normal fault occurs when the crust is extended. Alternatively such a fault can be called an extensional fault. The hanging wall moves downward, relative to the footwall. A downthrown block between two normal faults dipping towards each other is called a graben. An up thrown block between two normal faults dipping away from each other is called a horst. Low-angle normal faults with regional tectonic significance may be designated detachment faults. A reverse fault is the opposite of a normal fault — the hanging wall moves up relative to the footwall. Reverse faults are indicative of shortening of the crust. The dip of a reverse fault is relatively steep, greater than 45°.

Fun Facts!! • One famous transform boundary is the San Andreas Fault in California • The Mariana Trench is the deepest part of the ocean • Scientists are now able to track the movement of tectonic plates using GPS. • In some places, the plates are pulling apart. New crust is pushed up from below. These are called divergent boundaries and they create rifts or valleys. Large lakes sometimes form in rifts.

Summary • Well as you can see plate tectonics affect our earth in many ways, for example, to sum it up, faults, folds, crust, spheres, all those things affect our climate, volcanic activity, temperature, and oceans. Also every year geographic workers have to change tectonic plate sizes every year!!

Cites • http: //study. com/academy/lesson/the-continentalcrust-definition-formation-composition. html • https: //www. britannica. com/science/oceanic-crust • https: //en. oxforddictionaries. com/definition/lithosp here • https: //www. britannica. com/science/asthenosphere • http: //www. thefreedictionary. com/folding • www. ducksters. com/science/earth_science/plate_te ctonics. php