Module 6 - Earth Science - Exogenic and Endogenic Process PDF

Earth Science Governor Pack Road, Baguio City, Philippines 2600 Tel. Nos.: (+6374) 442-3316, 442-8220; 444-2786; 442-2564; 442-8219; 442-8256; Fax No.: 442-6268 Science Technology Engineering and Mathematics Email: email@u...

Earth Science Governor Pack Road, Baguio City, Philippines 2600 Tel. Nos.: (+6374) 442-3316, 442-8220; 444-2786; 442-2564; 442-8219; 442-8256; Fax No.: 442-6268 Science Technology Engineering and Mathematics Email: [email protected]; Website: www.uc-bcf.edu.ph MODULE 2 Grade 11 Finals ENDOGENIC AND EXOGENIC PROCESSES Module outline Endogenic and Exogenic Processes  Introduction  Endogenic Processes o Weathering o Erosion  Exogenic Processes o Volcanism o Earthquake Module objectives At the end of the module, the learners should be able to: a. Describe how rocks undergo weathering and explain how the products of weathering are carried away by erosion and deposited elsewhere. b. Describe how rocks behave under different types of stress such as compression, pulling apart, and shearing. c. Create a reflection on the important insight of the module through a story board. INTRODUCTION Exogenic processes include geological phenomena and processes that originate externally to the Earth's surface. They are genetically related to the atmosphere, hydrosphere and biosphere, and therefore to processes of weathering, erosion, transportation, deposition, denudation etc. Exogenic factors and processes could also have sources outside the Earth, for instance under the influence of the Sun, Moon etc. The above-mentioned processes constitute essential landform-shaping factors. Earth’s surface provides a harsh environment for rocks. Most Image Source: rocks originate under much higher temperatures and https://lh3.googleusercontent.com/proxy/58 pressures and in very different chemical settings than those dBgUjtY9rsboysNXlDlHqLKsiTz_c0e4rCtLT867gS found at Earth’s surface. Thus, surface and near-surface 4a_oVQ1vK0FHvCHiigKPcIcP8BrGBmURh_uD4 conditions of comparatively low temperature, low pressure, FDNmBRp2fzanJg69p5q2eU6tQ and extensive contact with water cause rocks to undergo varying amount of disintegration and decomposition. Endogenic processes are caused by endogenic factors or agents supplying energy for activities that are located within the Earth or below the Earth’s surface. They refer to the movement of the Earth’s lithosphere resulting to formation of landforms. The endogenic processes of Earth are responsible for earthquakes, movement of plates leading to development of continents, mountain building, volcanic activities and other movements related to Earth’s crust. EXOGENIC PROCESSES I. WEATHERING Environmental conditions at and near Earth’s surface subject rocks to temperature, pressures and substances, especially water, that contribute to physical and chemical breakdown of exposed  Earth Science Governor Pack Road, Baguio City, Philippines 2600 Tel. Nos.: (+6374) 442-3316, 442-8220; 444-2786; 442-2564; 442-8219; 442-8256; Fax No.: 442-6268 Science Technology Engineering and Mathematics Email: [email protected]; Website: www.uc-bcf.edu.ph MODULE 2 Grade 11 Finals rock. Broken fragments of rock, called clasts that detach from the original rock mass can be large or small. These detached pieces continue to weather into smaller particles. Fragments may accumulate close to their source or be widely dispersed by mass wasting and the geomorphic agents. Many weathered rock fragments become sediments deposited in such landforms as floodplains, beaches, or sand dunes, whereas others blanket hillslopes as regolith, the inorganic portion of soils. Weathering is the principal source of the inorganic constituents of soil, without which most vegetation could not grow. Likewise, ions chemically removed from rocks during weathering are transported in surface or subsurface water to other location. Ions represent a major source of nutrients in terrestrial as well as aquatic ecosystems, including rivers, ponds, lakes, and the ocean. The several types of rock weathering fall into two basic categories. Physical weathering, also known as mechanical weathering, disintegrates rocks, breaking smaller fragments from a larger block or outcrop rock. Chemical weathering decomposes rock through chemical reactions that remove ions from the original rock-forming minerals. Many different physical and chemical processes lead to rock weathering, and water plays an important role in almost all of them. A. Physical Weathering Mechanical weathering or physical weathering is the physical breakdown of a rock into unconnected grains or chunks without changing its composition. This occurs in several ways:  A rock formed underground experiences high confining pressure. When this rock is brought to the surface by uplift, the high pressure is released due to removal of overburden. As a result, natural cracks or joints are formed, breaking the rock into rectangular blocks or irregular chunks or onion-like sheet. Intrusive rock such as granite usually split into onion-like sheets parallel to the surface in a process called exfoliation. Image Source: https://i.ytimg.com/vi/x-taMPWMTI4/maxresdefault.jpg  In temperate regions or high altitudes, water inside the fracture of rocks experience regular freezing and thawing. When it freezes, it causes the joints to expand and grow, causing pieces of rocks to detach. This process is called frost wedging. Image Source: https://media.sciencephoto.com/image/c0055123/800wm  Joints also expand when plants growing on its surface pry it opens in a process called root wedging.  Earth Science Governor Pack Road, Baguio City, Philippines 2600 Tel. Nos.: (+6374) 442-3316, 442-8220; 444-2786; 442-2564; 442-8219; 442-8256; Fax No.: 442-6268 Science Technology Engineering and Mathematics Email: [email protected]; Website: www.uc-bcf.edu.ph MODULE 2 Grade 11 Finals Image Source: https://blogs.agu.org/mountainbeltway/files/2014/03/IMG_2264.jpg  In desert or along coastal areas, salt solutions from groundwater or from sea spray can accumulate in the pore spaces and fractures of rocks. When the salt crystallizes, it pushes apart the surrounding grains and weakens the rock, causing it to disintegrate when exposed to wind or rain. This process is called salt wedging. Image Source: https://images.slideplayer.com/13/4150127/slides/slide_14.jpg  Thermal expansion occurs when a rocks is exposed to high temperature such as a forest fire; is outer layer expands due to baking. When it cools, the outer layer contracts, causing the surface to break-off into sheets. Burrowing animals also push open cracks and move rock fragments. Human activities, such as digging and blasting, also contribute significantly to physical weathering. Image Source: https://images.slideplayer.com/25/7633008/slides/slide_2.jpg B. Chemical Weathering Chemical weathering occurs when there are chemical changes in at least some of the composition of the rock. It is a surface or near-surface process that is not influenced by high temperature or pressure. The chemical reactions occur at a faster rate in warm, wet climates like in the tropics. The common chemical reactions that occur in rocks are the following:  Dissolution happens in certain minerals which are dissolved in water. Halite (NaCl) dissolves rapidly in pure water while calcite (CaCO3) dissolves rapidly in acidic water like rainwater. Limestone, which is composed of calcite, is weathered through this process and develops caves though time.  Hydrolysis occurs when water reacts with the minerals and breaks them down. The process occurs faster in slightly acidic water. The common rock-forming minerals like amphibole, pyroxene, and feldspar all react with water and form various types of clay minerals.  Earth Science Governor Pack Road, Baguio City, Philippines 2600 Tel. Nos.: (+6374) 442-3316, 442-8220; 444-2786; 442-2564; 442-8219; 442-8256; Fax No.: 442-6268 Science Technology Engineering and Mathematics Email: [email protected]; Website: www.uc-bcf.edu.ph MODULE 2 Grade 11 Finals  Oxidation, or the reaction of oxygen with minerals in the rock, forms oxides. Oxidation of iron- bearing minerals like biotite and pyrite produce iron oxide (hematite) and iron hydroxide (goethite).  Hydration occurs when water is absorbed into the crystal structure of the mineral, causing it to expand. Certain types of clay expand through this process.  Biological weathering also occurs in roots of plants, when fungi and lichens secrete organic acids that dissolve minerals and the nutrients are taken in by these organisms. There are also certain bacteria that consume certain minerals. Physical and chemical weathering occurs simultaneously in disintegrating the rocks to form sediments. However, rock types do not weather at the same rate when exposed to the surface. Soft rocks like shale weather faster than hard rocks like sandstone. This creates indentations in rock slopes composed of alternating soft and hard rock layers. Weathering is an important process in the formation of soil. The products of weathering, along with organic matter, form the soils that host primary producers that sustain life on Earth. II. EROSION Erosion is the separation and removal of weathered and unweathered rocks and soil from its substrate due to gravity or transporting agents like wind, ice, or water. It involves abrasion, plucking, scouring, and dissolution. Transport is the process by which sediments are moved along from the source to where they are deposited.  Wind Erosion- commonly occurs in flat, bare areas or dry, sandy, and loose soils. It detaches soils particles and transports them by wind. Sandstorms are common phenomenon in deserts that transports lots of sediments for hundreds of kilometers. Wind erosion damages the land and natural vegetation by removing soil from one place and depositing it in another area such as farmland or built-up areas. It results to soil loss, dryness, and deterioration of soil structure, soils nutrients and productivity losses, and air pollution. The sand dunes in Paoay, Ilocos Norte are formed through this process. Image source: https://3.bp.blogspot.com/_1Fsg3DXeb8A/S7vAEt6HS9I/AAAAAAAACHA/KUzQuShTLCA/s1600 /la+paz+sand+dunes.jpg  Glacier is a permanent body of ice, which consists largely of recrystallize snow and shows evidence of movement due to gravity. Glaciers have enormous erosive power. As rock moves over a rock, it acts like a bulldozer; the rocks and soil at the surface are scraped off and grinded against the mixture of ice and rocks. It moves slowly but erodes downward rapidly, forming U- shaped valleys. This erosion process is dominant in Polar Regions and in high altitude mountains.  Earth Science Governor Pack Road, Baguio City, Philippines 2600 Tel. Nos.: (+6374) 442-3316, 442-8220; 444-2786; 442-2564; 442-8219; 442-8256; Fax No.: 442-6268 Science Technology Engineering and Mathematics Email: [email protected]; Website: www.uc-bcf.edu.ph MODULE 2 Grade 11 Finals Image source: https://i.ytimg.com/vi/vekqCga4XjE/hqdefault.jpg  Water is the most common erosion agent. Millions of tons of sediments are picked-up and transported everyday along rivers, coasts, and in deep oceans around the world. Sediments move along in four ways:  Traction -- rolling or dragging of large grains aided by the push of smaller grains.  Saltation – bouncing of sand grains as they are picked-up along, and dropped repeatedly.  Suspension – movement of fine particles like silt and clay.  Solution – movement of soluble minerals (salts). Rivers start as small individual streams, called tributaries, in elevated areas such as mountains, forming V- shaped valleys. They have strong erosive power and carry large angular sediments such as boulders and cobbles (fist sized sediments). In wider and gentler valleys, the sediments transported get smaller and smoother, becoming dominantly pebbles and sand. In the lowlands, rivers bends and deposition happens inside the meander. The sediments consist mainly of sand and mud. As the river enters the sea, it separates into many branches, called distributary channels, and deposits most of its sediment load, forming the tidal flats composed of sand and mud. III. MASS WASTING Mass wasting or mass movement is the downslope movement of rock, soil, and ice due to gravity. It is also a natural hazard that can cause damage to life and property. The factors that contribute to the occurrence of mass wasting are the following: 1. Relief- the difference in elevation between two places creates slopes; gravity pulls materials at higher elevations to lower elevations. 2. Slope stability- the balance between the downslope force caused by gravity and the resistance force due to friction; slope failure occurs when the downslope force is greater. 3. Fragmentation and weathering- intact rock is held together by chemical bonds within minerals, by mineral cement, and by interlocking of grains, while a fragmented rock is held only by friction between planes or by weak electrical charges between grains. Mass wasting can be classified in a number of ways such as type of materials, type of motion, and speed of movement. In general, the types of materials include rock and soil. Predominantly coarse soli materials are called  Earth Science Governor Pack Road, Baguio City, Philippines 2600 Tel. Nos.: (+6374) 442-3316, 442-8220; 444-2786; 442-2564; 442-8219; 442-8256; Fax No.: 442-6268 Science Technology Engineering and Mathematics Email: [email protected]; Website: www.uc-bcf.edu.ph MODULE 2 Grade 11 Finals debris while predominantly fine materials are labeled as earth. The general types of motion include fall, topple, slide, spread, and flow. 1. Fall includes the free fall movement, bouncing, and rolling of materials on a slope. 2. A topple is the forward rotation out of the slope of a soil or rock mass. The rotation axis is usually at the base of the moving mass, below its center of gravity. 3. A slide is the downslope movement of coherent materials along a well-defined surface of rupture called sliding surface. A slide could form a planar or curve sliding surface. 4. Spread is the lateral extension and fracturing of a coherent mass due to the plastic flow of its underlying material. This could occur as slit layers liquefy during earthquake. 5. Flow happens when the materials are saturated and move downslope as a viscous fluid. 6. Complex or combinations of several types of movements could occur. IV. DEPOSITION The sediments produced by weathering, which were separated by erosion and transported by different agents, will eventually settle down in a particular place given the right conditions. Deposition is the process in which sediments out of the transporting medium. When glacier melts, the rocks are deposited on the ground. The layer formed when the materials are laid down is called bed. It varies in the thickness depending on the volume of the sediments. The distribution of grain size in a layer is called sorting. If the beds consist only of one or two similar grain size, it has good sorting (well sorted). If the grain size consists of a mixture of very fine (clay-size) and very coarse (boulder- size) grains, it exhibits poor sorting. A layer can also have gradational change in grain size when there is a sequential variation such as from coarse to fine. In a mixture with various grain size, the larger sediments are called clasts and the surrounding fine-grained sediments are referred to as matrix. The area where sediments are deposited is called sedimentary environment. Some of these environments are the following: 1. Glacial environment – Glacial environments refer to areas where glaciers and ice sheets are found such as in high altitude mountains and in polar regions. At the end of glacier, a pile of sediments, ranging from clay to boulder-size, mixed together can be found and it is called glacial till. Image Source: https://openpress.usask.ca/app/uploads/sites/29/2018/03/Receding_glacier_landscape_L MB.png 2. Mountain stream environment – turbulent streams can carry large sediment like boulders and cobbles during flood, forming thick gravel and boulder layers. Conglomerates usually form in this environment. 3. Mountain front environment – when a stream enters the flat area at the base of a mountain, it loses energy and decreases velocity. This results to a landform called alluvial fan which is primarily composed of sand- to boulder-size sediments. 4. Desert environment – wind carries sand and silt materials. When deposited, well-sorted sand produce sand dunes, while the accumulation of silts form loses deposit. Sediments from solutions called evaporites are also formed when temporary lakes in the desert dry-up. 5. Lake (lacustrine) environment – a lake is a quiet environment. Streams carrying sediments deposits coarse sediments on lake margins, only silt and clay are deposited from suspension in deeper parts of the lake. Shale can form in this environment.  Earth Science Governor Pack Road, Baguio City, Philippines 2600 Tel. Nos.: (+6374) 442-3316, 442-8220; 444-2786; 442-2564; 442-8219; 442-8256; Fax No.: 442-6268 Science Technology Engineering and Mathematics Email: [email protected]; Website: www.uc-bcf.edu.ph MODULE 2 Grade 11 Finals Image Source: https://image2.slideserve.com/4220088/slide1-l.jpg 6. River (fluvial) environment – in flat areas, rivers are slow moving and commonly carry an assortment of pebbles, sand, silt, and mud. The coarser sediments tumble along the river bed while finer ones move along in suspension. Mud is deposited on the floodplain after flood events. Pebbles and sand are deposited on the inner bend of meander. Beds of sand and pebble form lenses alternating with silt and mud layer. Image Source: https://www.nps.gov/subjects/geology/images/3Zones_Fluvial_1204- 2018_tte-01.jpg 7. Delta environment – when a river enters the sea, it empties its load in a delta, which extends to shallow coastal area. The upper part of the delta consists mostly of coarse sand and gravel; the middle portion contains fine sand and silt, and the basal portion is mostly silt and clay. Mud is also found in the swamps. Image Source: https://www.glossary.oilfield.slb.com/en/~/media/PublicMedia/OGL98125- t.ashx 8. Beach environment – tidal currents transport sands along the coastline. The waves winnow out the finer sediments, leaving only well-sorted and well-rounded sand grains that form ripples. 9. Shallow marine environment – the mud and silt removed from the shoreline and from river mouths are transported by tidal currents and deposited in quieter waters below the wave zone. It forms well-sorted and well-rounded silt and mud layers inhabited by various organisms like worms and mollusks.  Earth Science Governor Pack Road, Baguio City, Philippines 2600 Tel. Nos.: (+6374) 442-3316, 442-8220; 444-2786; 442-2564; 442-8219; 442-8256; Fax No.: 442-6268 Science Technology Engineering and Mathematics Email: [email protected]; Website: www.uc-bcf.edu.ph MODULE 2 Grade 11 Finals Image Sources: https://media.springernature.com/original/springer- static/image/chp:10.1007/978-3-642-38800- 2_13/MediaObjects/309719_1_En_13_Fig18_HTML.gif 10. Shallow water carbonate environment - in shallow marine environment where the supply of sediments is limited, marine organisms like coral reefs develop where the water is fairly warm, clear, and full of nutrients. Most of the sediments are derived from the shell and coral fragments collectively called carbonate sediments. Limestone can be formed in this environment. Image Source: https://www.researchgate.net/profile/Azeem_Hussain3/publication/310830809/figure/fig6/ AS:669516837167108@1536636661165/Digenetic-processes-in-shallow-marine-environments- Meteoric-water-flushing-and-water.png 11. Deep marine environment – slope failure from the steep slopes of submarine canyons generates submarine landslides which create sediments of varying size. Turbidity currents carry the finer sediment components, ranging from sand to clay to a submarine fan where turbidite deposit/ sequence is formed. In the deep ocean floor, clay and planktons settle down and form very thin layers of mud. Chalk is formed from very calcite shells while chert is derived from siliceous shells.  Earth Science Governor Pack Road, Baguio City, Philippines 2600 Tel. Nos.: (+6374) 442-3316, 442-8220; 444-2786; 442-2564; 442-8219; 442-8256; Fax No.: 442-6268 Science Technology Engineering and Mathematics Email: [email protected]; Website: www.uc-bcf.edu.ph MODULE 2 Grade 11 Finals As layers of sediments accumulate in the different depositional environments, the previously deposited sediments underneath is buried. The sedimentary environment also sinks slowly to accommodate more sediment. The buried sediments experience compaction due to increasing pressure and the grains are packed tighter. Dissolved chemicals in the water occupying the pore spaces in between the grains precipitate and form new minerals called cement. This process which binds together the individual grains is called cementation. Some minerals are also recrystallizing, and recrystallization are referred as diagenesis. The sediments undergo lithification, when those changes occur and become sedimentary rocks. SHARE YOUR THOUGHTS! House bill 8728: Graduation Legacy for the Environment Act The house of representatives has supported a measure mandating all graduating elementary, high school, and college students to plant at least 10 trees each as a prerequisite for graduation. House bill 8728 or the “Graduation Legacy for the Environment Act” is authored by reps. Gary Alejano and Strike Revilla has been approved on third and final reading at the lower house and shall be transmitted to the Senate for action. The bill’s authors said “it is the policy of the State to pursue programs and projects that promote environmental protection, biodiversity, climate change mitigation, poverty reduction, and food security”, also the bill said, “to this end, the educational system shall a locus for propagating ethical and sustainable use of natural resources among the young to ensure the cultivation of a socially-responsible and conscious citizenry.”. With this being said and as a senior high student, what are your thoughts regarding this matter? Are you in favor? Or are you against? If so, what are the pros and cons of this House bill 8728? Article Source: https://www.denr.gov.ph/images/news_clippings/News_Clippings_05_16_2019.pdf ENDOGENIC PROCESSES Volcanoes and Volcanism Volcanoes Lithosphere is divided into several plates. These plates drift slowly over the mantle below, which is lubricated by a soft layer called asthenosphere. The process at the boundary between some of these plates is the one responsible for magma production among volcanoes. A volcano is a mountain that opens downward to a reservoir of molten rock called magma below the surface of the Earth. They differ from most mountains because they have vents where molten rocks escapes to the Earth’s surface during volcanic eruptions. Volcanic landforms are controlled by the geological processes that formed them and act on them even after they have formed. There are more than 1,500 volcanoes on Earth that have the potential to become active, as they have already erupted within the past 10, 000 years. Most volcanoes can be found only on designated narrow bands that are suitable for the completion of the three stages of a volcano’s life cycle. These three stages are invasion of magma, pressure building, and eruption.  Earth Science Governor Pack Road, Baguio City, Philippines 2600 Tel. Nos.: (+6374) 442-3316, 442-8220; 444-2786; 442-2564; 442-8219; 442-8256; Fax No.: 442-6268 Science Technology Engineering and Mathematics Email: [email protected]; Website: www.uc-bcf.edu.ph MODULE 2 Grade 11 Finals About 95% of the world’s volcanoes are located near the boundaries of tectonic plates while the remaining 5% are thought to be associated with mantle plumes and hotspots. Hotspots and mantle plumes were first observed in the 1960s. During this period, geologists were set on various explorations to either prove or disprove the theory of moving plates. During his visit in Hawaii, Canadian geophysicist John Tuzo Wilson and one of the founders of the founders of the theory of plate tectonics noticed some interesting features about the ocean islands. He found three linear chains of volcanoes and submarine volcanoes (seamounts) which are separated by thousands of miles from each other. When he studied the reports and recorded the age of each island, Wilson found an interesting pattern – the islands become progressively younger to the southeast. At the end of the chain, at the extreme southeast, he found active volcanoes. His theory states that volcanic chains like the Hawaiian Islands result from the slow movement of tactic plate across a fixed hotspot. Mantle plumes are areas or columns where heat or rocks in the mantle are rising toward Earth’s surface. They can be located underneath continental or oceanic crust or along plate boundaries. They are thought to spread out laterally at the base of a continent that allowed an increase in pressure that stretches the crust, resulting to an uplift, a fracture or a rift. Hotspots are locations on Earth’s surface that have experienced active volcanic activities for a long period of time. Hotspots are thought to be caused by the convection of hot mantle at the mantle plumes. The region is fed by the underlying mantle from which heat rises as a thermal plume inside the earth. Rocks within a hotspot melt and become a magma due to high temperature and low pressure at the base of the tectonic plate. These hot magmas will then rise through a crack and erupt to form volcanoes. As the tectonic plate moves over the stationary hotspot, the volcanoes are rafted away and new one’s form in their respective places. As the ocean floor floats over this zone, the upwelling lava creates a steady succession of new volcanoes that move along with the plate. There are about 40-50 identified hotspots in world. Geologists have identified the Galapagos Islands, Hawaii, Iceland, Reunion, and Yellowstone as some of the most active hotspots at the present. Volcanism Volcanism is one of the most impressive displays of Earth’s dynamic internal processes. From a human perspective, volcanism can be a destructive force causing property damage, injuries, fatalities, and atmospheric changes. From a geologic perspective, volcanism is a constructive process that builds oceanic islands, produces oceanic crust, provides parent material for highly productive soils, and releases the gases that formed Earth’s early atmosphere and surface waters. Volcanism refers to the processes and phenomena associated with the surficial discharge of molten rock and other materials into the surface of Earth and other heavenly bodies such as the moon and other planets in the solar system. Where are volcanoes formed? Volcanoes are generally found where tectonic plates are pulled apart or come together. Active volcanism occurs in four principal settings. a. Divergent Plate Boundaries  A mid-oceanic ridge, for example the Mid-Atlantic Ridge, has examples of volcanoes caused by “divergent tectonic plates” pulling apart.  Black smokers or deep-sea vents are an example of this kind of volcanic activity.  Where the mid-oceanic ridge is above sea-level, volcanic islands are formed, for example, Iceland. b. Convergent Plate Boundaries  The Pacific Ring of Fire has examples of volcanoes caused by “convergent tectonic plates” coming together.  Earth Science Governor Pack Road, Baguio City, Philippines 2600 Tel. Nos.: (+6374) 442-3316, 442-8220; 444-2786; 442-2564; 442-8219; 442-8256; Fax No.: 442-6268 Science Technology Engineering and Mathematics Email: [email protected]; Website: www.uc-bcf.edu.ph MODULE 2 Grade 11 Finals  Subduction zones are places where two plates, usuallt an oceanic plate and a continental plate, collide.  In this case, the oceanic plate subducts, or submerges under the continental plate performing a deep ocean trench just offshore.  Typical examples for this kind of volcanoes are Mount Etna and the volcanoes in the Pacific Ring of Fire. c. Non-hotspot/ Intraplate Volcanism  Volcanoes can also form where there is stretching and thinning of the Earth’s crust such as in the o a. African Rift Valley o b. the Wells Gray-Clearwater Volcanic Field and the Rio Grande Rift in North America and o c. the European Rhine Graben with its Eifel volcanoes d. Hotspots  Volcanoes can be caused by “mantle plumes”. These so called “hotspots” can occur far from plate boundaries.  Hotspots are not usually located in ridges of tectonic plates, but above mantle plumes, where the convection of Earth’s mantle creates a column of hot material that rises until it reaches the crust, which tends to be thinner than in other areas of the Earth.  The Hawaiian Islands are thought to be formed in such a manner, as well as the Snake River Plain, with the Yellowstone Caldera being the part of the North American plate currently above the hotspot. Types of Volcanoes 1. Shield volcanoes  Shield volcanoes are named for their broad, shield-like profiles. They are formed by the eruption of low viscosity lavas that can flow a great distance from a vent, but generally explode catastrophically.  The Hawaiian volcanic chain is a series of shield volcanoes and they are common in Iceland, as well. 2. Lava domes  Lava domes are built by slow eruptions of highly viscous lavas. They are sometimes formed within the crater of a previous volcanic eruption (as in Mount Saint Helens), but can also form independently, as in the case of Lassen Peak.  Like stratovolcanoes, they can produce violent, explosive eruptions, but their lavas generally do not flow far from the originating vent. 3. Volcanic cones/ Cinder cones  Earth Science Governor Pack Road, Baguio City, Philippines 2600 Tel. Nos.: (+6374) 442-3316, 442-8220; 444-2786; 442-2564; 442-8219; 442-8256; Fax No.: 442-6268 Science Technology Engineering and Mathematics Email: [email protected]; Website: www.uc-bcf.edu.ph MODULE 2 Grade 11 Finals  Volcanic cones or cinder cones result from eruptions that erupt mostly small pieces of scoria and pyroclastics (both resemble cinders, hence the name of this volcano type) that build up around the vent.  These can be relatively short-lived eruptions that produce a cone-shaped hill perhaps 30 to 400 meters high.  Most cinder cones erupt only once.  Cinder cones may form as flank vents on larger volcanoes, or occur on their own.  Paricutin in Mexico and Sunset Crater in Arizona are examples of cinder cones. 4. Stratovolcanoes/ Composite volcanoes  Stratovolcanoes are tall conical mountains composed of lava flows and other ejecta in alternate layers, the strata give rise to the name.  Stratovolcanoes are also known as composite volcanoes. These are made of cinders, ash and lava. Cinders and ash pile on top of each other, then lava flows on top and dries and then the process begins again.  Classic examples include Mt. Fuji in Japan, Mount Mayon in the Philippines, and Mount Vesuvius and Stromboli in Italy. 5. Supervolcano  Supervolcano is the popular term for a large volcano that usually has a large caldera and can potentially produce devastation on an enormous, sometimes continental scale.  Such eruptions would be able to cause severe cooling of global temperatures for many years afterwards because of the huge volumes of sulfur and ash erupted.  They are the most dangerous type of volcano. Examples include Yellowstone Caldera in Yellowstone National Park of western USA, Lake Taupo in New Zealand and Lake Toba in Sumatra, Indonesia. Earthquakes An earthquake is a natural phenomenon that is characterized by a sudden, violent shifting of massive plates underneath Earth’s surface. This movement of plates release stress that generates along geologic faults. The Philippines is prone to earthquakes because of the numerous numbers of faults within the country. Therefore, it is already given that the Philippines would experience a lot of geologic hazards. Most earthquakes occur at the boundaries where the plates meet. It can also occur within plates. Although plate-boundary earthquakes are much more common. Less than 10 percent of all earthquakes occur within the plate interiors. Anatomy of an Earthquake  Earth Science Governor Pack Road, Baguio City, Philippines 2600 Tel. Nos.: (+6374) 442-3316, 442-8220; 444-2786; 442-2564; 442-8219; 442-8256; Fax No.: 442-6268 Science Technology Engineering and Mathematics Email: [email protected]; Website: www.uc-bcf.edu.ph MODULE 2 Grade 11 Finals Earthquakes are forms of wave energy that are transmitted through the bedrock. The point within the earth along the geological faults where earthquake originates is called hypocenter (focus). The point on the earth’s surface directly above the focus is called the epicenter. Seismic waves start to radiate from the hypocenter and subsequently form along the fault rupture. When the hypocenter is located near the surface, from 0 to 70 km, shallow-focus earthquakes are produced. Earthquakes with focal depths from 70 to 300 km are classified as intermediate. If it exceeds from 300 km up to 700 km, deep-focus earthquakes are produced. As shallow-focus earthquakes are closer to the surface where rocks are stronger and could build up greater strain, these earthquakes are larger and more damaging compared to deep-focus earthquake. Two general types of vibrations: Seismic waves are classified into two: surface waves and body waves. A. Body Waves  Waves that travel below the surface of the Earth.  They are of two types: compressional or primary (P) waves and shear or secondary (S) waves. Both waves are called body waves because they can travel through the interior of the Earth from the focus to distant points on the surface. P waves travel the fasted at a speed between 4-8 km/s at Earth’s crust; hence, they are the first to arrive at a location. S waves usually travel at 2.5-4 km/s and can only travel through solid materials unlike the P waves, which can move through all states of matter.  During earthquakes, we hear sounds coming from the ground. These waves are actually the P waves, which are commonly hear but seldom felt. P waves shake the ground in the direction they are propagating, while S waves shake the ground perpendicularly, causing more damage to the surface above it. B. Surface Waves  Waves that can only travel along the surface. They arrive after the P waves and S waves and are confined to the outer layers of the Earth.  Earth Science Governor Pack Road, Baguio City, Philippines 2600 Tel. Nos.: (+6374) 442-3316, 442-8220; 444-2786; 442-2564; 442-8219; 442-8256; Fax No.: 442-6268 Science Technology Engineering and Mathematics Email: [email protected]; Website: www.uc-bcf.edu.ph MODULE 2 Grade 11 Finals  Surface waves are classified into two: love and Rayleigh. Love waves move transverse to the direction of the propagation but with no vertical motion. They cause rocks to move horizontally or side to side at right angles to the directions of the traveling wave. Rayleigh waves, also called ground roll, because rock particles to move upward, up, backward, and down in a path that contains the direction of the wave travel. Love waves cause the most damage to buildings and structures. Types of Earthquakes Geologists also classified earthquakes depending on the region where each occurs and the geological make-up of that region. 1. Tectonic Earthquake  Happens when the shifting of Earth’s plates are driven by the sudden release of energy within some limited region of the rocks of Earth. The energy can be released by elastic strain, gravity, movement of massive bodies, or chemical reactions.  Occurs when strains in rock masses have accumulated to a point where the resulting stress exceeded the strength of the rocks, resulting to sudden fractures that eventually propagate through rocks in rapid motion. 2. Volcanic Earthquake  This phenomenon occurs in volcanic regions and can serve as an early warning of volcanic eruptions. Volcanic earthquakes are caused by either the injection or withdrawal of magma in response to the changes in pressure in the rock where the magma has experienced stress. They are comparatively less common than the tectonic earthquakes.  There are two types of volcanic earthquakes: the volcanic tectonic earthquakes, which occur after a volcanic activity has taken place, and the long-period volcanic earthquake that occurs after a volcanic eruption. A few days before the great explosion, the change in heat of magma below Earth’s surface created seismic waves, causing an earthquake. 3. Collapse Earthquake  Caused by seismic waves produced from the explosion of rocks on the surface. Collapse earthquakes are small earthquakes located underground and in mines that are caused by the disintegration of the roof of the mine or cavern or by massive land sliding.  An often-observed variation of this earthquake type is the “mine (rock) burst”. It is believed that the occurrence of mine bursts increases as the depth of the mine increases. Hundreds of miners die in mine bursts annually, and mining is considered one of the deadliest industries at present.  Earth Science Governor Pack Road, Baguio City, Philippines 2600 Tel. Nos.: (+6374) 442-3316, 442-8220; 444-2786; 442-2564; 442-8219; 442-8256; Fax No.: 442-6268 Science Technology Engineering and Mathematics Email: [email protected]; Website: www.uc-bcf.edu.ph MODULE 2 Grade 11 Finals 4. Explosive Earthquake  It is an earthquake that results from detonation of chemicals or nuclear devices. Explosion occurs when enormous nuclear energy is released during underground nuclear explosions. In a millionth of a second after a nuclear device is detonated in a borehole underground the pressure jumps thousands of times the pressure of the atmospheric pressure, and the temperature increases by millions of degrees. Measuring Seismic Waves  Seismologists use the seismograph to detect the presence of an earthquake and its magnitude.  Traditionally, geologists use the Mercalli and the Richter scales to assign magnitude to earthquakes.  Mercalli Scale – invented by Giuseppe Mercalli in 1902. This scale uses observation of the people who experience the earthquakes to estimate its intensity. However, this was not considered scientific.  Richter Scale – also known as the local magnitude (M L) scale. Introduced by Charles F. Richter in 1934. Assigns a single number to quantify the amount of seismic energy released by an earthquake. Richter Mercalli Description Earthquake Effects Not felt except by a very few under especially favorable I Instrumental conditions, detected mostly by seismography 2 Felt only by a few persons indoors, especially on upper floors of II Feeble buildings Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an III Slight earthquake. Idle cars may rock slightly. Vibration is similar to the passing of a truck. 3 Felt indoors by many, outdoors by few during the day. At night, there would be some awakening. Dishes, windows, doors are IV Moderate disturbed; walls make cracking sound. Sensation is like a heavy truck striking a building. Idle cars rock noticeably. Felt by nearly everyone; many awakened. Some dishes and 4 V Rather Strong windows are broken. Unstable objects overturned. Pendulum ducks may stop. Felt by all. Some heavy furniture moved; a few instances of VI Strong fallen plaster. Slight damage. Damage noticeable in buildings of good design and 5 construction; slight to moderate in well-built structures; VII Very Strong considerable damage in ordinary structures; considerable damage in poorly built or bad designed structures. Slight damage in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. 6 VIII Destructive Great damage in poorly built structures. Fall of factory stacks, columns, monuments, and walls. Heavy furniture’s are overturned. Considerable damage in specially designed structures; well- designed frame structures thrown out of plumb. Great IX Ruinous damage in substantial buildings, with partial collapse. Buildings 7 shifted off foundations, Some well-built wooden structures are destroyed; most X Disastrous masonry and frame structures destroyed with foundations. Rails bend greatly.  Earth Science Governor Pack Road, Baguio City, Philippines 2600 Tel. Nos.: (+6374) 442-3316, 442-8220; 444-2786; 442-2564; 442-8219; 442-8256; Fax No.: 442-6268 Science Technology Engineering and Mathematics Email: [email protected]; Website: www.uc-bcf.edu.ph MODULE 2 Grade 11 Finals Few, if any (masonry) structures remain standing. Bridges XI Very Disastrous destroyed. Rails bent greatly. 8 Total damage. Lines of sight and level distorted. Objects XII Catastrophic thrown into the air. References:  Valdoz, M.P., Aquino, M.D., Biong, J.A. & Andaya, M.O.(2017).Earth Science. Sta. Mesa Heights, Quezon City. Rex Publishing House, Inc.  Bawang, E., Dolipas, B., Lubrica, J., & Ramos, J. (2014). Lecture Manual in Physical Science (Earth Science).  OLIVAR II, J. et al (2016) Exploring Life through Science Earth Science. P136-147. Phoenix Publishing (Quezon Avenue, Quezon City)  OWEN, C. et Al. (2016) Earth Science. P255-286. Rex Book Store Inc. (Sampaloc, Manila, Philippines)