EARTHS-INTERNAL-HEAT2.pdf

Earth’s Internal Heat The Lesson is divided into two topics, namely: Lesson 1 – Earth’s Internal Heat Lesson 2 – Magmatism After going through this lesson, you are expected to: 1. Identify the sources and significance of the Earth's internal heat 2. Explain the requirements for magma generation...

Earth’s Internal Heat The Lesson is divided into two topics, namely: Lesson 1 – Earth’s Internal Heat Lesson 2 – Magmatism After going through this lesson, you are expected to: 1. Identify the sources and significance of the Earth's internal heat 2. Explain the requirements for magma generation 3. Describe the process in magma formation. Earth’s Internal Heat To become a metamorphic, it requires conditions of increased temperature and/or increased pressure, conversion to sedimentary rocks occurs via the intermediate stage of sediments, and conversion to igneous rocks occurs via the intermediate stage of magma: Sediments can be produced when rocks are uplifted, weathered and eroded, and the resulting detrital material deposited in (nakakasira) marine or terrestrial basins. capable of being shaped or bent or drawn out.  If the sediments are buried under further layers of other sediment, they can become lithified or cemented together to produce a sedimentary rock. Magma is formed when rocks are melted. This melting will occur when a lithospheric plate descends into the Earth’s crust at a subduction zone, or when a mid-ocean ridge opens up and produces decompression melting in the asthenosphere under the ridge. As magma solidifies, it becomes an igneous rock.  Earth's Internal Heat Source The formation of the Earth, which estimated about 4.5 billion years ago, was a very dynamic process. During the early age of Earth, it was an extremely hot and volatile place. The processes by which helped form our Planet Earth so long ago continue to affect the formation of Earth today. These processes include gravity and radioactivity.  Remember that the Earth formed in the process of accretion. The energy from these high velocity impacts was converted to heat energy. Heat is trap within the Earth and it is one part of the Earth's internal heat source. Gravity is the cause of internal compaction of the Earth and as a result heat up internally. The heat that was trapped in the Earth is released to the surface little by little. Radioactive decay occurs as radioactive elements break down in long period of time.  Elements trapped during the early formation of the Earth are subjected to radioactive decay. Radioactive heat (the heat generated by long-term radioactive decay): its main sources are the four long-lived isotopes (large half-life), namely K40, Th232, U235 and U238 that made a continuing heat source over geologic time. Heat transfer is the movement of thermal energy from a place with higher temperature to a cooler one. The three ways of heat transfer are conduction, convection, and radiation. SEAT WORK: Which of which? Directions. Identify the sources of internal heat by writing RH for radiogenic heat and PH for primordial heat. Write your answer on a separate sheet of paper. ____1. Presence of different isotopes of heat producing element in the mantle and crust. ____2. Internal heat accumulated by dissipation of planet. ____3. Release of accretional energy. ____4. Processes involved in mantle convection. ____5. Release of thermal energy as a result of spontaneous nuclear disintegration  Heat Movement through Convection and Conduction Based on the activity, Simulating Convection, the top portion has a relatively lighter color, compared to the lower part of the cup. As time goes by, the entire hot water within the cup becomes uniform in color. This represents the convection process.  The reality is that the temperature gradient is much lower in the main part of the mantle compare with the lithosphere has been interpreted as evidence of convection in the mantle. When heat within the mantle convects, heat is transferred through the mantle by physically moving hot rocks.  Mantle convection is the product of heat transfer from the core to the base of the lower mantle. As with a pot of water on a hot stove in the figure to your right, the material near the heat source becomes hotter and expands, making material above denser compared to the material near the source.  Buoyancy causes it to rise, and cooler material flows in from the sides downward. Convection in the pot is much faster than convection in the mantle. Mantle convection happens at rates of centimeters per year.  Convection makes the heat transfer to the surface of the mantle much faster as compare to the process of heating by conduction. Conduction is a process of heat transfer by colliding molecules, and the same process on how heat is transferred from the stove to the pot of water  A mantle that is convecting is an essential feature of plate tectonics, because the higher rate of heat transfer is necessary to keep the asthenosphere weak. Earth’s mantle will stop convection process once the core reaches lower temperature to the point where the process of heat transfer cannot overcome the strength of the rock. This phenomenon happened on smaller planets like Mercury and Mars, as well as on Earth’s moon. When mantle convection stops, the end of plate tectonics activity will follow.  Temperature gradient describes the direction and rate at which temperature changes in each area. The temperature gradient is a dimensional quantity expressed in units of degrees (on a particular temperature scale) per unit length. For example, the temperature at the western edge of the map is 75 degrees Fahrenheit and the temperature at the eastern edge is 50 degrees Fahrenheit. Mantle convection is the slow movement of Earth's solid silicate mantle due to convection currents carrying heat from the interior to the surface. It is the main way heat from Earth’s interior is transported to its surface. Mantle convection drives tectonic plate movements and volcanic activity WHAT I HAVE LEARNED 1. Heat is trap within the Earth and it is one part of the Earth's internal heat source. 2. Gravity is the cause of internal compaction of the Earth and as a result heat up internally. The heat that was trapped in the Earth is released to the surface little by little. 3. Radioactive decay occurs as radioactive elements break down in long period of time. Elements trapped during the early formation of the Earth are subjected to radioactive decay. 4. Heat transfer is the movement of thermal energy from a higher temperature place with a cooler one. The three ways of heat transfer are conduction, convection, and radiation. 5. Convection occurs at the mantle, but not between the core and mantle, or even between the asthenosphere and lithosphere (except at sea-floor spreading zones). The only heat transfer mechanism in these transition zones is through conduction. Magma Formation Taal Volcano This eruption does not erupted last January 12, 2020. only emit gases, it also released magma. In this There are emission of gases from lesson, you will learn the volcano and dust particles. how this magma forms underneath the volcano Aside from gases, what do you think or under the surface of are the other material released the Earth. by the volcano?  crater ash ash cloud parasitic cone vent lava flank lava flow throat summit (apex) sill conduit pipe branch pipe magma chamber(reservoir) crust  Majority of the mantle is made of extremely is consist of magma. hot liquid and semi-liquid This magma can rock located under the move through opening surface of the Earth. Earth is or cracks in the earth’s a layered structure that crust, this is called consists of the crust, volcanic eruption. mantle, outer core and inner core. Magma When magma moves or The high erupts onto the surface of temperatures and the earth, this magma will pressure under become lava. Magma is a Earth’s crust keep mixture of different minerals, just like an magma in its fluid ordinary solid rock. It also state. Magma and contains small amounts of lava contain three dissolved gases components: melt, such as solids, and water vapor, volatiles. carbon dioxide, and sulfur. The melt is made of Volatiles are gaseo ions from minerals that components— such have liquefied. The solids water vapor, carb are made of crystallized dioxide, sulfur, a minerals floating in the chlorine—dissolved liquid melt. These may the mag be minerals that have already cooled Basic Types of Magma All types of magma have a significant amount of silicon dioxide. Basaltic magma is made up mostly of iron, magnesium, and calcium but low in potassium and sodium. It ranges in temperature from about 1000’C to 1200’C (1832oF to 2192oF). has moderate Andesitic magma amounts of these minerals, with a temperature range from about 800oC to 1000oC (1472oF to 1832oF).  Rhyolitic magma is high in potassium and sodium but low in iron, magnesium, and calcium. It exist in the temperature range of about 650oC to 800oC (1202oF to 1472oF). Both the temperature and mineral content of magma affect how easily it flows  2) flux melting caused by adding volatiles and There are three principal ways rock behavior to 3) heat-induced create molten magma: melting caused 1) decompression melting by increasing the caused by lowering the temperature. pressure, The Bowen’s Reaction some minerals are Series shows that minerals melted and some melt at different remain solid. This temperatures. Since type of rock magma is a mixture of behavior is called different minerals, the partial melting and solidus boundary is more represents real-world of a fuzzy zone rather than magmas, which typically a well-defined line; contain solid, liquid, and volatile components.  Magma can be created at mid-ocean ridges via decompression melting. The Strong convection currents cause the solid asthenosphere to slowly flow beneath the lithosphere.  The upper part of the lithosphere (crust) is described as a poor heat conductor, so the temperature is constant throughout the underlying mantle material.  Where the convection currents make the mantle material to rise, the pressure decreases, which causes the melting point to drop. In this scenario, the rock at the temperature of the geothermal gradient is rising toward the surface, thus hotter rock is shallower, … …at a lower pressure, and the rock, still at the temperature of the geothermal gradient at its old location, shifts past its melting point and partial melting starts. As this magma continues to rise, it cools and crystallizes to form new lithospheric crust.  Fluid-induced Melting Occurs in island arcs and subduction zones when volatile gases are added to mantle. Flux- melted magma produces many of the volcanoes in the circum-Pacific subduction zones, also known as the Ring of Fire. The subducting slab contains oceanic lithosphere and hydrated minerals. These hydrated forms are created when water ions bond with the crystal structure of silicate minerals.  As the slab descends into the hot mantle, the higher temperature causes the hydrated minerals to emit water vapor and other volatile gases, which expelled from the slab-like water emitted out of a sponge.  Transforming solid mantle into liquid magma by simply applying heat is the basic common process for generating magma. It occurs at the mantle plumes or hotspots. The rock surrounding the plume is subjected to higher temperatures, the geothermal gradient crosses to the right of the green solidus line, and the rock begins to melt.  The mantle plume includes rising mantle material, meaning some decompression melting is occurring as well. A small amount of magma is also generated by intense regional metamorphism. This magma becomes a hybrid metamorphic- igneous rock called migmatite.  Because the mantle is composed of many different minerals, it does not melt uniformly. As minerals with lower melting points turn into liquid magma, those with higher melting points remain as solid crystals. This is known as partial melting. As magma slowly rises and cools into solid rock, it undergoes physical and chemical changes in a process called magmatic differentiation.  Each mineral has a unique melting and crystallization temperature. Since most rocks are made of many different minerals, when they start to melt, some minerals begin melting sooner than others. This is known as partial melting and creates magma with a different composition than the original mantle material. What Have I Learned 1. Crust and mantle are almost entirely solid, indicating that magma only forms in special places where pre-existing solid rocks undergo melting. 2. Melting due to decrease in pressure (decompression melting): The decrease in pressure affecting a hot mantle rock at a constant temperature permits melting forming magma. This process of hot mantle rock rising to shallower depths in the Earth occurs in mantle plumes, beneath rifts and beneath mid-ocean ridges. What Have I Learned 3. Melting as a result of the addition of volatiles (flux melting): When volatiles mix with hot, dry rock, the volatile decreases the rock’s melting point and they help break the chemical bonds in the rock to allow melting. 4. Melting resulting from heat transfer from rising magma (heat transfer melting): A rising magma from the mantle brings heat with it that can melt the surrounding rocks at the shallower depths.