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The core is divided into two parts, the solid inner core and the liquid outer core. The inner core is thought to be solid and primarily made up of iron and some nickel. The outer core is all around the inner core and is believed to be made up of liquid iron mixed with liquid nickel. The outer core is about 2890 to 5100 km.
The inner core is 5100 to 6378 km. Earths mantle is mainly composed of substances high in iron and magnesium. The melting point of every substance depends on the pressure and the deeper we go the higher the pressure becomes. Because of this the upper mantle is said to be semi-molten and the lower mantle solid. The upper mantle iron-substances are semi-molten because it is hot and they are under little pressure, lower mantles iron-substances are solid because they are under a lot of pressure. The mantle is 35 to 2890 km.
Earths crust ranges from 5 to 70 km in depth. The thinnest parts are the oceanic crust made of dense iron magnesium silicate rocks and underlie the ocean basins. The thicker crust is continental crust, composed of sodium potassium aluminum silicate rocks. The crust varies from 0 to 35 km or 5 to 70 km.
Convection currents occur because the density of a fluid is related to its temperature. Hot rocks lower in the mantle are less dense than the cooler rocks above. The hot rocks rise and the cooler rocks sink because of gravity. Convection currents are thought to be the driving mechanism of plate movement. Convection currents cause convergent and divergent movements. When the rising part of the convection current rises it causes the upper mantle to move upward and in a lateral direction.
This causes the mantle to split and new material to rise creating new ocean crust. The downward motion of the convection current pulls the mantle crust downward at convergent boundaries. When part of the mantle crust is uplifted the weight of the lifted part, pushes the sinking mantle down, causing motion in the tectonic plates. A convergent boundary is where two tectonic plates move towards each other.
And when they collide they form either a subduction zone with its associated island arc or an orogenic belt and associated mountain range. When the two plates collide, one of the plates is pushed underneath the other. This then forms oceanic trenches in which the Earth's crust is pushed under into the mantle where it becomes molten. The oceanic trenches are several hundred kilometers long but narrow. They also are the deepest parts of the ocean floor. These boundary types also produce mountains.
Mountains are made when convergent boundaries collide but instead of one going under they both are pushed up by the others force. For this to happen neither of the boundaries can be more or less dense than the other. There are three types of convergent boundaries: oceanic plate-continental plate convergence, oceanic plate-oceanic plate convergence, and continental-continental plate convergence. An example of this type of boundary is the collision between the Eurasian Plate and the Indo-Australian Plate which is forming the Himalayas.
A divergent boundary is where the plates are moving away from each other. These areas can form in the middle of continents but eventually form ocean basins. Divergent boundaries make ocean ridges like the Mid- Atlantic ridge. At divergent boundaries the floor is higher than anything else around it. This is because where the plates are moving away from each other there is a crack where new magma constantly flows upward toward the surface through a gap called a rift onto the ocean floor making the surrounding area move outward.
Sometimes submarine volcanoes might also be formed. Continental crust is often split along divergent plate boundaries. An oceanic ridge is an underwater mountain range, usually formed by plate tectonics. Abyssal plains are flat or very gently sloping areas of the ocean basin floor where rocks slowly sink into the ground because they have no heat energy supporting them below.
They result from the layering of an uneven surface of the ocean floor with fine-grained sediments like clay and silt deposited from turbidity currents. They usually form in between the foot of a continental rise and a mid-oceanic ridge. A transform boundary happens when tectonic plates slide and grind against each other along a transform fault. As the plates slide past each other the grinding and scraping start forming cracks and faults. An example of this is the San Andres fault in California. Most transform boundaries are found on the ocean floor, where they often offset active spreading ridges to form a zigzag plate boundary.
A few transform boundaries occur on land. Earthquakes are a trembling or a shaking movement of the Earth's surface. Earthquakes typically result from the movement of faults. The Earthquakes hypocenter is the point where the fault slips, and where the quake first started. The fault may slip far from its epicenter, though. Larger faults are capable of higher magnitude earthquakes than smaller faults are.
Earthquakes occur where the stress is more than the capacity of Earths materials to support it. This happens more often at the boundaries of the tectonic plates. Some earthquakes are also caused by the movement of magma in volcanoes, and such quakes can be an early warning of volcanic eruptions. Most volcanoes on land are formed where oceanic crust is pushed below the continental crust at a convergent boundary. As it move downward the friction and the heat will start melting the oceanic crust. Magma has a low density, so the newly formed magma will be forced upward.
It rises up through cracks and weak areas in the continental crust, this will eventually make a new volcanoes. A hotspot is where the Earth's surface has experienced active volcanoes for a long time. Volcanic chains result from the slow movement of a tectonic plate across a 'fixed' hot spot deep beneath the surface of the planet. A seamount is a mountain rising from the seafloor that does not reach to the surface of the ocean. Seamounts are often found in groupings or submerged archipelagos. They are formed by volcanism.
Isolated seamounts and those without clear volcanic origins appear to be less common. Fracture zones are where there was some type of activity that caused that rock to break. They are usually produced from earthquakes or volcanoes. They are also from moving tectonic plates. They are usually around the edges of the tectonic plates.
An ocean current is a directed movement of ocean water that flows in one of the Earth's oceans. Currents can flow thousands of kilometers. They are also very important in determining the climates of the continents. Surface ocean currents are generally wind driven and develop their typical clockwise spirals in the northern hemisphere and counter-clockwise rotation in the southern hemisphere due to the Coriolis Effect. Deep ocean currents are driven by density and temperature gradients. These currents that flow under the surface of the ocean, and are hidden from immediate detection, are called submarine rivers.
Oceans cover almost three quarters of the earth's surface. They are all a connected body, called the World Ocean. They are somewhat divided by the continents into the Pacific, Atlantic, Indian and Arctic. The World Ocean is 361 million km^ 2 in area, the volume is 1370 million km^ 3, and its average depth is 3790 m.
The landmasses are divided into seven continents. They are Africa, Antarctica, Asia, Australia, North America, South America and Europe. But before there were seven it was said to be just one giant landmass called Pangaea. Supposedly this super continent began to break up about 225 - 200 million years ago, eventually coming into the position the continents are today.
Similar fossils of several different animals and plants that once lived on land had been found widely separated on the continents. There would be no way that these could have gotten where they were found if the continents were then as they are now. Works cited 1. ) History of Plate Tectonics - web 2. ) Earth Structure web layers/Earths layers 4. html 3. ) Earth Science Book -copyright 2002 by the McGraw-Hill Companies, Inc.
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Research essay sample on Tectonic Plates Oceanic Crust
