The Earth's Internal Heat and Magmatism PDF

The Earth’s Internal Heat Prepared by: Ms. Lorenze Anne F. Madrigal Earth and Life Science Adviser  Heat energy plays a vital role in our planet. It is one of the extreme factors in what makes the world liveable. Our planet's internal heat shifts continents, creates mount...

The Earth’s Internal Heat Prepared by: Ms. Lorenze Anne F. Madrigal Earth and Life Science Adviser  Heat energy plays a vital role in our planet. It is one of the extreme factors in what makes the world liveable. Our planet's internal heat shifts continents, creates mountains, and produces earthquakes. Basically, the Earth has 3 main layers, these are Crust, Mantle and  The Crust of the earth is a very thin layer when compared to the 3 other layers. The Mantle is the largest layer of the earth with estimated 1800 miles thick. The mantle is composed of very hot dense rock called magma, because of the high temperatures with the Mantle, the rock is kept in a semi-liquefied state. The Outer Core is composed of liquefied metals such as nickel and iron. It is kept in it liquefied state because of the immense heat in this layer.  The Inner Core is also composed of metals however they are not kept in a liquefied state. It is believed that the temperature and pressure at depth is so great that the metals are squeezed tightly together restricting movement, so much that the particles have to vibrated in place almost like a solid structure.  Sources of heat in our planet can be identified as Primordial and Radiogenic heat. During the early formation of the Earth, the internal heat energy that gradually gathered together by means of dispersion in the planet during its few million yearsof evolution is called Primordial heat. The major contribution of this internal heat is the accretional energy – the energy deposited during the early formation of a planet. The core is a storage of primordial heat that originates from times of accretion when kinetic energy of colliding particles was transformed into thermal energy.  This heat is constantly lost to the outer silicate layers of the mantle and crust of the earth through convection and conduction. In addition, the heat of the core takes tens of thousands of years to reach the surface of the earth. Today, the surface of the earth is made of a cold rigid rock since 4.5 billion years ago, the earth’s surface cools from the outside but the core is still  The thermal energy released as a result of spontaneous nuclear disintegration is called Radiogenic Heat. It involves the disintegration of natural radioactive elements inside the earth – like Uranium, Thorium and Potassium.  Estimated at 47 terawatts (TW), the flow of heat from Earth’s interior to the surface and it comes from two main sources in equal amounts: the radiogenic heat produced by the radioactive decay of isotopes in the mantle and crust, and the primordial heat left over from the formation of the Earth. Radioactive elements exist everywhere on earth in a fairly significant concentration. Without the process of radioactive decay, there would be fewer volcanoes and earthquakes – and less  Both sources of heat whether primordial or radiogenic undergo heat transfer and it plays an important role to the continuous changes and development of our planet. Three processes can transfer heat: conduction, convection, and radiation. Conduction Conduction processes happen in the earth’s surface and it directs the thermal settings in almost entire solid portions of the Earth and plays a very important role in the lithosphere. One of the three main ways of heat transfer is conduction. Technically, it can be defined as the process by which heat energy is transmitted through collisions between neighboring atoms or molecules. Conduction carries heat from the Earth's core and radiation from the Sun to the Earth's surface. When the atmosphere in normal temperature contacts with the warm surfaces of the land, it transfer thermal energy, then it will heats up the rest of the Conduction Conduction is the process by which heat energy is transmitted through collisions between neighboring atoms or molecules. Conduction occurs more readily in solids and liquids, where the particles are closer together than in gases, where particles are further apart. The rate of energy transfer by conduction is higher when there is a large temperature difference between the substances that are in contact. Some solids, such as metals, are good heat conductors. Not surprisingly, many pots and pans have insulated handles. Air (a mixture of gases) and water are poor conductors of thermal energy. They are called insulators. Conduction in the Atmosphere Since air is a poor conductor, most energy transfer by conduction occurs right near Earth's surface. Conduction directly affects air temperature only a few centimeters into the atmosphere. During the day, sunlight heats the ground, which in turn heats the air directly above it via conduction. At night, the ground cools and the heat flows from the warmer air directly above to the cooler ground via conduction. Conduction in the Atmosphere On clear, sunny days with little or no wind, air temperature can be much higher right near the ground than slightly above it. Although sunlight warms the surface, heat flow from the surface to the air above is limited by the poor conductivity of air. A series of thermometers mounted at different heights above the ground would reveal that air temperature falls off rapidly with height. Convection Convection is the transfer of heat by the movement of mass, and it is a more effective mode of heat transport in the Earth than pure conduction. Convection dominates the thermal conditions in zones with significant amounts of fluids (molten rocks) and thus governs the heat transport in the fluid outer core and the mantle. In geological time scale, due to the tremendous temperature, the mantle acts like a viscous fluid. In convection current, the mantle of the earth moves slowly because of transfer of heat from the interior of the earth up to the surface. This results to the movement of tectonic plates. Hot materials are added at the edges of a plate and then it cools. At those edges, it becomes dense by its exposure from the heat and sinks into the earth at an ocean trench. This starts the formation of volcanoes. Radiation Radiation is the least important mode of heat transport in the Earth. The process of heat exchange between the Sun and the Earth, through radiation, controls the temperatures at the Earth's surface. Inside the Earth, radiation is significant only in the hottest parts of the core and the lower mantle. When the land and water become warm in summer, it emits long – wavelength infrared radiation that is readily absorbed by the atmosphere. This continues during night time too. Convection in the air then spreads out the thermal energy Magmatism Prepared by: Ms. Lorenze Anne F. Madrigal Earth and Life Science Adviser  Magma is composed of semi-liquid hot molten rocks located beneath the Earth, specifically in the melted mantle rock and oceanic plate. This molten state, when solidified, creates igneous rocks found on the surface of the Earth. Magma and lava are both molten rocks. However, they differ in location. Magma is found in the magma chamber of the volcano while is found on the surfa lava ce of earth once the volcano erupts.  Magmatism is a process under the earth’s crust where formation and movement of magma occur. These happen in the lower part of the Earth’s crust and in the upper portion of the mantle, known as  The magma present in the lower crust and upper mantle of the Earth is formed or generated through the process of partial melting. In this process, different minerals in rock melt at different temperature and pressure. Another factor being considered in this process is the addition of Melting in the mantle requires one of three possible events to occur: 1. An increase in temperature 2. A decrease of pressure 3. Addition of volatiles 1. An increase in temperature Conduction in mantle happens when heat is transferred from hotter molten rocks to the Earth’s cold crust. This process is known as heat transfer. As magma rises, it is often hot enough to melt the rock it touches. It happens at convergent boundaries, where tectonic plates 1. An increase in temperature Rocks are composed of minerals. These rocks start to melt once the temperature in the lower crust and upper mantle increases or exceeds the melting point of minerals. The temperature of mantle is around 1200 degrees Celsius. Rock minerals such as quartz and feldspar begin to partially melt at around 650-850 2. A decrease of pressure Mantle rocks remain solid when exposed to high pressure. However, during convection, these rocks tend to go upward (shallower level) and the pressure is reduced. This triggers the melting of magma. This is known as decompression melting. This process occurs at the Mid-Ocean Ridge, an underwater mountain system. 3. Addition of volatiles When water or carbon dioxide is added to hot rocks, flux melting occurs. The melting points of minerals within the rocks decrease. If a rock is already close to its melting point, the effect of adding these volatiles can be enough to trigger partial melting. It occurs