Geology Handouts PDF

GEOLOGY HANDOUTS WEEK 1 What is GEOLOGY - one of the most tactile and hands-on interdisciplinary field which studies the earth’s physical structure. - deals with many practical questions about our physical environment, what forces produce different geological structures, understa...

GEOLOGY HANDOUTS WEEK 1 What is GEOLOGY - one of the most tactile and hands-on interdisciplinary field which studies the earth’s physical structure. - deals with many practical questions about our physical environment, what forces produce different geological structures, understanding many processes that operate beneath and upon its surface. - is the science that studies Earth: how it was born, how it evolved, how it works, and how we can help preserve its habitats for life. - The word Geology is derived from the Greek "Gea" the earth and "logoss" the science, thus it is "Earth Science". 2 MAIN BRANCHES OF GEOLOGY 1. Physical Geology - concerned with the work of natural processes which bring about changes upon the earth’s surface 2. Historical Geology -study of earth’s geologic past; the study of both stratigraphy and paleontology; to know about the land and seas, the climate and the life of early times upon the earth. OTHER BRANCHES OF GEOLOGY 1. Crystallography – the study of crystals; to recognized the minerals; o Crystal – is a regular polyhedral form bounded by smooth surfaces. 2. Mineralogy – the study of minerals; importance: (a) for a civil engineering student to identify the rocks. (b) in industries such as cement, iron, and steel, fertilizers, glass industry and so on. (c) in the production of atomic energy. o Mineral – defined as a naturally occurring, homogeneous solid, inorganically formed, having a definite chemical composition and ordered atomic arrangement. 3. Petrology – the study of rocks; the selection of suitable rocks for building stones, road metals, etc. o Rock – defined as the aggregation of minerals found in the earth’s crust. 4. Structural Geology – the study of structures found in rocks, also known as tectonic geology or simply tectonics; is an arrangement of rocks and plays an important role in civil engineering in the selection of suitable sites for all types of projects such as dams, tunnels, multistoried buildings, etc. 5. Stratigraphy – the study of stratified rocks and their correlation. 6. Paleontology – the study of fossils and the ancient remains of plants and animals are referred to as fossils. o Fossils – are useful in the study of evolution and migration of animals and plants through ages, ancient geography and climate of an area. 7. Economic Geology – the study of minerals, rocks and materials of economic importance like coals and petroleum. 8. Civil Engineering Geology – the study of application of geology to mining engineering in such a way that the selection of suitable sited for quarrying and mines can be determined. 9. Mining Geology 10. Hydrology Geology – the studies of both quality and quantity of water that are present in the rocks in different states; (a) Atmospheric water, (b) Surface water, and (c) Underground water. 11. Resources Engineering – the study of water, land, solar energy, minerals, forests, etc. fulfill the human wants. 12. Photo Geology – the study of aerial photographs. WEEK 2 Earth’s entire history is divided into 4 MAJOR DIVISIONS named in ‘abstract time’ 1. Eon - largest division 2. Era - Precambrian Time (oldest)-Paleozoic-Mesozoic-Cenozoic (youngest era) 3. Period 4. Epoch - smallest division What is the ATMOSPHERE? - is the outer part of the Earth System that extends nearly 500 km above Earth's surface and includes an ever-changing mixture of gas and small particles surrounding the Earth’s surface. - It includes meteorological features and phenomena such as weather, clouds, or aerosols (particles in the air). Geologic Time Scale - a standard timeline and important tool to portray the history of the earth. EXTERNAL STRUCTURE of the EARTH: Spheres of the Earth 1. Atmosphere - layer above the lithosphere and hydrosphere a. Troposphere - lowest layer of the atmosphere b. Stratosphere c. Mesosphere d. Thermosphere e. Exosphere 2. Biosphere - the ecosphere; also known as the ‘zone of life’; distinguishes Earth from all other planets in our solar system as life evolved (and continues to evolve) since Earth's early history between 4.5 and 3.8 billion years ago. 3. Cryosphere - contains huge quantities of ice at the poles and elsewhere; refers to any place on Earth where water is in its solid form, where low temperatures freeze water and turn it into ice. 4. Geosphere/Lithosphere - also known as ‘land’; is associated with solid portions of the Earth. o 94% of the solid Earth is made up of the following elements: oxygen, iron, silicon, and magnesium. o Plate Tectonics - movement creates continents, oceans, and their landforms. 1  5. Hydrosphere - the layer of water surrounding the lithosphere; is associated with water in the liquid state, which covers about 70% of the Earth's surface; gives Earth a distinct appearance as a blue marble and separates us from other planets in the solar system. INTERNAL STRUCTURE of the EARTH 1. Crust - consists of continental and oceanic crust separated by Conrad discontinuity. 2. Mantle - is separated from earth crust by Moho Discontinuity. 3. Upper Mantle - It exists between the crust and the transition zone. This layer is hard and brittle and is where tectonic plates exist. 4. Inner Core - It is estimated to be of about 850 km in thickness; It is solid with the same composition and contains very high- density materials with an average density 17 gm/cm3. 5. Outer Core - It surrounds the inner core which is liquid, its composition is similar to that of the inner core, mainly iron and nickel; It is of 2100 km in thickness and average density 10-15 gm/cm3. Discontinuity - The boundary between these envelopes which indicates to changes in properties DISCONTINUITIES IN THE EARTH’S LAYERS 1. Conrad Discontinuity - separates the upper and lower crust 2. Mohorovicic (Moho) Discontinuity - the transition zone between the crust and the mantle; It was discovered by Mohorovicic in 1909 by observing the break in the velocity of seismic waves. 3. Repetti Discontinuity - separates the upper mantle from the lower mantle THEORIES: UNIFORMITARIANISM VS CATASTROPHISM - Uniformitarianism (James Hutton) ▪ “The Present is the Key to the Past” ▪ assumes that the chemical and physical laws of nature have not changed through Earth’s geologic past/history. ▪ also called Theory of Gradualism ▪ is the assumption that the chemical and physical laws of nature have not changed over the course of Earth’s long history. ▪ Beauty: is that it allows us to use observations of the modern world to understand Earth’s history. - Catastrophism ▪ suggested the features seen on the surface of Earth, such as mountains, were formed by large, abrupt changes—or catastrophes. ▪ proposes the idea that catastrophes are responsible for mass extinctions and other processes. ▪ Charles Lyell successfully challenged the principle of catastrophism ▪ Catastrophism (Baron Georges Cuvier) WEEK 3 What is TECTONIC PLATE? - are composed of the oceanic lithosphere and the thicker continental lithosphere, each topped by its own kind of crust. Along convergent plate boundaries, the process of subduction carries the edge of one plate down under the other plate and into the mantle. CONTINENTAL DRIFT THEORY - sought to explain how continents shift position on Earth's surface - set forth in 1912 by German Meteorologist, Alfred Wegener PANNOTIA - It was formed by the agglutination of previous continental landmasses PANGAEA - was the only major landmass on Earth, and with a single large ocean filling the interior of the supercontinent, this caused very large-scale interactions between atmospheric circulation. - supercontinent which later broke up in the Jurassic period LAURASIA - It median on the Northern hemisphere with almost all landmasses in North America, Europe and Asia except for India. GONDWANA - was a southern hemisphere landmass comprising present-day South America, Africa, Antarctica, Australia and Indian subcontinent. EVIDENCES that support PLATE TECTONICS - Fossil Evidence o Mesosaurus - ancient reptile; found both in South America and in Africa o Glossopteris – its distinctive fern-like leaves, has been found in South America, Africa, Antarctica, and Australia. - Rock Formations and Geological Structures - Paleoclimatic Evidence - Past climatic evidence such as glaciers in areas that are now close to the Equator - Glacial striations - scratch the surfaces of rocks and other things that they float above. - Bituminous Coal - a type of fossil fuel which is made of compressed plant remains - continents fit together almost like puzzle pieces forming Pangaea - similar fossils and rock units on different continents - occurrence of earthquakes - continental and ocean floor features including mountains, volcanoes, faults, and trenches SEA FLOOR SPREADING - the process where the oceanic ridges spreads and moves away from the ridge axis with a motion like that of a conveyor belt as new lithosphere is created - occurs at DIVERGENT PLATE boundaries 2  - helps explain continental drift in the theory of plate tectonics - creates NEW CRUST CRUSTS 1. Continental Crust - the layer of igneous, sedimentary and metamorphic rocks (mostly granite); forms the continents and the areas of shallow seabed close to the shore (CONTINENTAL SHELVES); Lighter than oceanic crust 2. Oceanic Crust - uppermost layer of the oceanic portion of a TECTONIC PLATE (mostly basalt); Denser than continental crust. MID – OCEAN RIDGE - large mountain ranges rising from the ocean floor where SEA FLOOR SPREADING occurs. 1. Mid-Atlantic Ridge o separates the North American plate from the Eurasian plates o separates the South American plate from the African plate 2. East Pacific Rise o separates the Pacific plate from the North American plate, the Cocos plate, the Nazca plate, and the Antarctic plate 3. Southeast Indian Ridge o marks where the southern Indo-Australian plate forms a divergent boundary with the Antarctic plate. SUBDUCTION - destroys OLD CRUST - occurs at CONVERGENT PLATE boundaries - another part of PLATE TECTONICS occurs at SUBDUCTION ZONES, when tectonic plates crash into each other instead of spreading apart SUBDUCTION ZONES - zones where edge of denser plates subducts/slides’ goes down under the lighter or less dense one HOT SPOTS - spots where magma from the mantle concentrates and is capable of breaking through the Earth’s surface - DO NOT MOVE...the continental plate above them moves - builds an archipelago…volcano arcs as it goes PLATE TECTONICS - a SCIENTIFIC THEORY describing the large-scale motion of nine (9) large plates and the movements of a larger number of smaller plates of Earth's lithosphere - explains the features and movement of Earth's surface in the present and the past 3 FORCES as MAIN DRIVERS of Tectonic Plates 1. Ridge Push - gravitational force at the spreading ridges 2. Mantle Convection Currents - heat driven 3. Slab Push - gravitational force in subduction zones ALFRED WEGENER - German geophysicist and meteorologist credited as the first to develop a THEORYOFPLATETECTONICS, a modern version of the Continental Drift. ASTHENOSPHERE - the plastic-like layer of Earth below the lithosphere on which tectonic plates (lithospheric plates) float TECTONIC PLATES - also called lithospheric plate - is a massive, irregularly shaped slab of solid rock, generally composed of both 1. continental lithosphere/crust 2. oceanic lithosphere//crust 9 MAJOR TECTONIC PLATES 1. Pacific Plate - largest plate 2. Antarctic Plate - 2nd largest plate 3. South American Plate 4. North American Plate 5. African Plate 6. Eurasian Plate 7. Indian Plate 8. Indo-Australian Plate 9. Australian Plate PLATE BOUNDARIES 1. Divergent Plate boundary - plates rip or move apart (e.g., Baja, California) 2. Convergent Plate boundary - one plate dives (“subducts”) beneath the other, resulting in a variety of earthquakes and a line of volcanoes on the overriding plate (e.g., Taal Volcano) a. Continental-Continental collision (C-C) b. Oceanic-Continental (O-C) c. Oceanic-Oceanic (O-O) 3. Transform Plate Boundary - where plates slide laterally past one another in opposite directions (e.g., San Andreas Fault) CONVERGENT boundaries occur where plates push together. Because the plates are pushing together, crust is either FOLDED or CRUNCHED at the boundary. When one plate SUBDUCTS or goes under the lighter plate, it is called SUBDUCTION. 3  When two CONTINENTAL plates meet, it is called continental-continental collision. Because both crusts have the same DENSITY neither plate will sink below the other. If the plates keep moving, their edges will eventually CRUMPLE and FOLD. Sometimes, the folded crust pushes up to create MOUNTAINS. When an oceanic plate sinks under another oceanic plate it is called OCEANIC-OCEANIC subduction. The OLDER plate sinks because it is COLDER and DENSER than the plate on top. As the it sinks into the asthenosphere, it MELTS, getting destroyed and reabsorbed into the mantle. OCEAN TRENCH - area that shows where the plate disappears and where subduction zones are found OCEANIC PLATES pulling apart would result in: - escaping magma to pile up and be extruded to the surface - magma would cool and turn into igneous rocks - mountains will be formed over a long period of time CONTINENTAL PLATES colliding against each other would result in: - Earthquakes - Area of collision of both plates will be lifted to form mountains WEEK 4 MINERALS - are essentially the building blocks of rocks; also called ‘NATIVE ELEMENTS’ HOW MINERALS are FORMED 1. crystallization from a solution - evaporation of a liquid solution 2. crystallization from magma 3. changes in heat and pressure CHARACTERISTICS OF MINERALS 1. inorganic 2. naturally-occurring 3. solid 4. specific or definite chemical composition 5. crystalline structure MINERAL GROUPS: Minerals are grouped by their chemical composition - Minerals that form the rocks within Earth’s crust belong to 7 Main Mineral Groups/Examples: 1. Silicate - Quartz, Feldspar, Olivine, Mica 2. Oxide - Hematite, Magnetite, Corundum 3. Sulfate - Gypsum, Barite, Anhydrite 4. Sulfide - Galena, Pyrite, Bornite 5. Carbonate - Calcite, Dolomite, Malachite, Azurite 6. Native elements - Silver (Ag), Copper (Cu), Gold (Au) 7. Halides - Halite (NaCl) PHYSICAL PROPERTIES OF MINERALS 1. Color - best described by using primary or simple colors, with descriptors and subsidiary colors added as necessary - least useful property when identifying minerals 2. Streak - color of a mineral when powdered and observed against an unglazed white porcelain plate (streak plate) 3. Hardness - a measure of the mineral’s resistance to scratching o FRIEDRICH MOHS - Austrian mineralogist who devised a scale based on one mineral's ability to scratch another (1822) - 1 (softest mineral-TALC), and 10 (hardest-DIAMOND) 4. Cleavage - describes how minerals break along certain plains of weakness in their crystal structure - How easily the cleavage is obtained: a. Perfect b. Good c. Imperfect - Direction of the cleavage surfaces: a. Cubic cleaves in 3 directions @ 90o to one another b. Rhombohedral cleaves in 3 directions but not @90o to one another c. Octahedral cleaves in 4 directions d. Dodecahedral cleaves in 6 directions e. Basal cleaves in 1 direction f. Prismatic cleaves in 2 directions 5. Fracture - describes the quality of the cleavage surface - It is the property of a mineral breaking in a more or less random pattern with no smooth planar surfaces a. Conchoidal - fracture surface is a smooth curve, bowl-shaped(common in glass) 4  b. Hackly - fracture surface has sharp, jagged edges. c. Uneven - fracture surface is rough and irregular. d. Fibrous - fracture surface shows fibres or splinters 6. Crystalline Structure - arrangement of the atoms, molecules or ions that make up the crystal and how they are joined (crystal lattice) a. Microcrystalline structure - can only be viewed using high magnification b. Cryptocrystalline structure - can only be viewed using high magnification c. Amorphous - If there is no crystalline structure; there are very few amorphous crystals; can only be observed under extremely high magnification 7. Luster - the property of mineral that indicates how much the surface of a mineral reflects light - luster of a mineral is affected by the brilliance of the light used to observe the mineral surface - Terms to describe LUSTER: a. Metallic - the mineral is opaque and reflects light as a metal wood b. Sub-metallic - the mineral is opaque and dull; the mineral is dark-colored c. Non-metallic - the mineral does not reflect light like a metal; are described using modifiers that refer to commonly known qualities: i. Waxy - the mineral looks like paraffin or wax ii. Vitreous - the mineral looks like broken glass iii. Pearly - the mineral appears iridescent, like a pearl iv. Silky - the mineral looks fibrous, like silk v. Greasy - the mineral looks like oil on water vi. Resinous - the mineral looks like hardened tree sap(resin) vii. Adamantine - the mineral looks brilliant, like a diamond 8. Transparency or Diaphaneity - a mineral’s degree of transparency or ability to allow light to pass through it - depends on the thickness of the mineral 9. Tenacity - describes how the particles of a mineral hold together or resist separation 10. Magnetism - allows a mineral to attract or repel other magnetic material 11. Odor - most minerals have no odor unless they are acted upon in one of the following ways: moistened, heated, breathed upon or rubbed 12. Taste - only soluble minerals have a taste, but it is very important that minerals not be placed in the mouth or on the tongue 13. Specific Gravity - a comparison or ratio of the weight of the mineral to the weight of an equal amount of water MOH’S SCALE OF HARDNESS ROCKS - the materials that form the essential part of the Earth’s solid crust. - hard mass of mineral matter comprising one or more rock-forming minerals - are formed from the cooling and crystallization of molten material (magma/lava) - importance: (a) make up earth’s crust and landscape (b) contain fossils and minerals that tell earth’s history PETROLOGY - the study of rocks (Greek: ‘petra’– rock; ‘logos’–science) deals with the description of rocks 5  PETROGENESIS - The study of the origin of rocks ROCK CYCLE - links the 3 MAIN GROUPS or TYPES of ROCKS through processes of formation and transformation 3 MAIN GROUPS or TYPES OF ROCKS 1. Igneous Rocks – can look different and have many different compositions, depending on how quickly they cool and solidify. 2. Sedimentary Rocks – are formed form the accumulation and compression of mineral and organic particles over time. o Types of Sedimentary Rocks a. Clastic – sandstone b. Chemical – limestone c. Organic - Coal 3. Metamorphic Rocks – are created when existing rocks are transformed by heat, pressured, or chemical processes. o Types of Metamorphic Rocks a. Foliated – slate b. Non-foliated - marble PROCESSES involved in the ROCK CYCLE - Internal Processes 1. Burial and compaction 2. Deformation and metamorphism (heat and pressure) 3. Uplift 4. Melting 5. Cooling 6. Crystallization of magma (solidification) - External Processes 1. Weathering Process a. weathering b. erosion c. transportation d. deposition e. lithification - compaction and cementation 2. Hydrologic Cycle The ROCK CYCLE is a never-ending cycle - it has no beginning and no end. ROCKS can change throughout many different processes through the rock cycle. RELATIONSHIPTS OF THE 3 TYPES OF ROCK 1. Igneous to Sedimentary - Igneous rocks, like basalt or granite, can be broken down by weathering and erosion into small particles. These particles are transported and deposited in layers, eventually compacting and cementing together to form sedimentary rocks like sandstone or shale. 2. Sedimentary to Metamorphic - Sedimentary rocks can be buried deep within the Earth, where they are subjected to intense heat and pressure. This process alters their structure and mineral composition, transforming them into metamorphic rocks, such as limestone becoming marble. 3. Metamorphic to Igneous - Metamorphic rocks can melt due to extreme heat, often associated with tectonic activity. When this molten material (magma) cols and solidifies, it forms new igneous rocks, completing the cycle. WEEK 5 MAGMA - contains mixture of minerals, small amounts of dissolved gases (H20 vapor, CO2, Sulfur) - high temp and pressure underneath the earth keeps magma in a FLUID state - will either be erupted to the top or may cool in place causing crystals to form and eventually solidify a. lighter SILICA-rich minerals > float tot the TOP b. heavier SILICA-rich minerals > go to the bottom PROPERTIES/CLASSIFICATION of MAGMA 1. Temperature - difficult to measure due to danger and risks involved 2. Density - Controlled by MAGMA COMPOSITION a. Basaltic Magma – rich in Fe (Iron), hence its dark color b. Rhyolitic Magma – rich in Silica, hence it light color c. Andesitic Magma – falls in between - Controlled by TEMPERATURE & PRESSURE a. High Temp: melts EXPAND b. Low Density & High Pressure: melts COMPRESS 3. Volatile Content - H20: most abundant volatile in most magmas - CO2: next most abundant volatile 6  4. Viscosity (thickness) - resistance to FLOW (opposite of FLUID) - depends primarily on: a. Magma Composition o higher SILICA content: higher viscosity o lower SILICA content: lower viscosity b. Temperature: viscosity decreases with increasing temperature of magma o low TEMP: higher viscosity o higher TEMP: lower viscosity - viscosity (thickness) of the magma that erupts from a volcano affects the shape of the volcano - very viscous (thick) magma: volcanoes with STEEP slope - less viscous magma: FLATTER volcanoes IGNEOUS ROCKS - formed through cooling, solidification and consolidation of molten material within(magma)oron the surface of earth (lava). BASES FOR CLASSIFICATION OF IGNEOUS Rocks 1. Texture a. Aphanitic - fine-grained b. Phaneritic - coarse-grained c. Porphyritic - large crystals embedded in fine-grained matrix d. Pyroclastic - consolidation of volcanic fragments e. Vesicular - contain voids left by bubbles as magma solidifies f. Glassy - resembles dark manufactured rx 2. Mineral Composition - Feldspar is the most common mineral found in igneous rocks - Basalt is the most common igneous rock - Others: olivine, quartz, amphibole, pyroxene, and muscovite 7  2 MAIN CATEGORIES of IGNEOUS ROCKS 1. Intrusive (Plutonic) Igneous Rocks o formed beneath the surface of the Earth’s crust, where magma COOLS SLOWLY, resulting in COARSE-GRAINED mineral grains. 2. Extrusive (Volcanic) Igneous Rocks o formed on the surface of the earth as a result of volcanic activity where it COOLS and CRYSTALLIZES RAPIDLY, resulting in FINE-GRAINED mineral grains. WEEK 6 VOLCANOES - an opening in the earth's surface where molten rock can escape - are closely associated with PLATE TECTONIC activity - can be active, dormant or extinct - are powerful agents of change…they can create new landforms, but they can also destroy everything in their path - The 2 types of plate boundaries that are most likely to produce volcanic activity: 1. divergent plate boundaries 2. convergent plate boundaries VOLCANISM - is the dynamic process of magma ascending from beneath Earth's crust to its surface. - This powerful phenomenon shapes our planet's landscape and creates volcanoes. As molten rock rises, it brings heat and pressure from deep within the Earth. TYPES OF VOLCANOES 1. Cinder Cones 2. Composite Volcanoes (Stratovolcanoes) 3. Shield Volcanoes 4. Lava Domes Volcanoes can be categorized into several types based on: - Shape - eruption style - the materials they erupt CATEGORIES of VOLCANIC ERUPTIONS 1. Effusive eruption - build up gently-sloping Shield volcanoes 2. Explosive eruption - build up more steeply-sloping Composite volcanoes VOLCANIC ERUPTIONS 1. Icelandic - often build lava plateaus 2. Hawaiian - form shield volcanoes (quite large and have gentle slopes) 3. Strombolian - moderate bursts of expanding gases that eject clots of in can descent lava in cyclical or nearly continuous small eruptions 4. Vulcanian - forms dark, turbulent eruption clouds that rapidly ascend and expand in convoluted shapes 5. Pelean - associated with explosive outbursts that generate pyroclastic flows, dense mixtures of hot volcanic fragments and gas 6. Plinian - intensely violent kind of volcanic eruption VOLCANIC HAZARDS 1. Tephra/ash 2. Lava Flows 3. Pyroclastic Density Currents 4. Pyroclastic Falls 5. Lahars - specific kind of mudflow made up of volcanic debris 6. Volcanic Gases 7. Volcanic landslides 8. Climate change STEPS IN MITIGATING VOLCANIC HAZARDS 1. Understanding what a volcano can do 2. How volcanic hazards behave 3. What can be done to avoid them COMMON VOLCANIC CHARACTERISTICS IN THE PHILIPPINES 1. Steep Conical Shapes - Many Philippine volcanoes are stratovolcanoes. They have distinctive cone-like profiles. 2. Frequently Activity - The region experiences regular eruptions. This is due to its position in the Pacific Ring of Fire. 3. Diverse Eruption Styles - Philippine volcanoes exhibit both effusive and explosive eruptions. This variety stems from differing magma compositions. TECTONIC FORCES DRIVING VOLCANIC ACTIVITY - Plate Convergence o Subduction zones create pressure and heat, melting rock into magma. - Plate Divergence o Spreading centers allow magma to rise, forming new crust. 8  - Mantle Plumes o Hot spots in the mantle generate magma, often far from plate boundaries. PLATE TECTONIC AND VOLCANISM IN THE PHILIPPINES 1. Philippine Mobile Belt - Complex tectonic region between major plates. Experiences frequent seismic and volcanic activity. 2. Subduction Zones - Philippine Sea Plate subducts beneath the Eurasian Plate. Creates volcanic arc along eastern Philippines. 3. Collision Zones - Taiwan-Luzon region experiences active collision. Contributes to volcanic and tectonic complexity. EXAMPLES OF VOLCANIC TYPES IN THE PHILIPPINES 1. Stratovolcano: Mount Mayon - Known for its perfect conical shape. Located in Albay Province. 2. Caldera: Taal Volcano – Complex volcano with a lake-filled caldera. Situated in Batangas Province. 3. Potentially Shield: Mount Isarog – Broad, shield-like volcano. Found in Camarines Sur Province. RELATION TO PLATE TECTONICS: TRENCHES, SUBDUCTION 1. Oceanic Plate Subduction - Philippine Sea Plate dives beneath the Eurasian Plate. Creates deep trenches along the eastern Philippines. 2. Magma Generation - Subducting plate releases fluids. This lowers the melting point of surrounding mantle rocks. 3. Volcanic Arc Formation - Rising magma forms a chain of volcanoes. Creates the distinctive Philippine volcanic arc. ASSOCIATED HAZARDS OF VOLCANISM - Lava Flows o Molten rock destroys everything in its path. Can cause long-term land use changes. - Ash Fall o Volcanic ash damages crops and infrastructure. Poses respiratory health risks. - Pyroclastic Density Currents o are mixtures of fragmented volcanic particles (pyroclastics), hot gases and ash that rush down the volcanic slopes - Debris Avalanche, Landslide o The mass failure of the flanks of a volcano edifice due to magma intrusion, a strong earthquake or the movements of faults beneath the edifice. - Volcanic Tsunami o occur in caldera lakes when water is displaced by deformation of the lake floor caused by rising magma or the entry of PDCs or landslides into the lake, or in seas when water is displaced by PDCs or debris avalanches from volcanoes. - Lahars o sometimes called volcanic mudflows or debris flows, are slurries of volcanic sediment, debris and water that cascade down a volcano’s slopes through rivers and channels. Volcanic mudflows are highly destructive. Often triggered by rainfall after eruptions. - Secondary Explosion o can be generated in still hot volcanic deposits such as those of PDCs and lava flow when these come into contact with water by erosion, rising groundwater or rainfall. ENGINEERING MITIGATION MEASURES 1. Monitoring Systems o Advanced seismic and gas monitoring equipment. Provides early warning of potential eruptions. 2. Hazard Mapping o Detailed maps of risk zones. Guides evacuation planning and land use decisions. 3. Diversion Structures o Engineered barriers and channels. Redirects lava flows and lahars away from populated areas. 4. Building Codes o Strengthened construction standards. Improves resilience to ash fall and seismic activity. WEEK 7 SEDIMENTARY ROCKS - formed by the accumulation of sediments - product of: 1. weathering of pre-existing rx 2. transport of the weathered products 3. deposition of the materials followed by LITHIFICATION: 4. compaction and 5. cementation of the sediment - the only type of rock that may contain fossils, or evidence of life 3 BASIC TYPES/CLASSIFICATION OF SEDIMENTARY ROCKS 1. Clastic/Detrital sedimentary rocks - made from pieces of rock (called clasts) that have been mechanically weathered 2. Chemical sedimentary rocks - form from the inorganic precipitation of minerals from a fluid (chemical weathering) 9  3. Organic sedimentary rocks - form from the accumulation and lithification of organic debris, such as leaves, roots, and other plant or animal Material (biological weathering) WEEK 8 WEATHERING - he physical and chemical breakdown/disintegration) of rocks at or near the surface–exposed to wind, water, ice, acids, salt, living organisms (plants...animals) and temperature 3 TYPES OF WEATHERING 1. Mechanical/Physical Weathering - disintegration (Ex: Sand Dunes and Rock Formations shaped by winds) 2. Chemical Weathering - decomposition (Ex: Carbonic Acid forms the shapes observed in caves) 3. Biological Weathering - disintegration + decomposition (Ex: Squirrels dig and create burrows in rocky areas) FACTORS that DIRECTLY INFLUENCE the RATE of WEATHERING 1. Temperature 2. Rock Type 3. Moisture Availability SOIL - The uppermost layer of the Earth's surface. - Is the result of weathering processes on the Earth's surface. - Consists of organic material, minerals, water, and air. - Form from transported material derived from elsewhere and deposited in a lowland or basin. REGOLITH - Residual soils develop on plains and lowlands with moderate to gentle slopes and consist of loose, heterogeneous material left behind from weathering. - This material may include particles of parent rock, clay minerals, metal oxides and organic matter. BEDROCK - The solid rock layer beneath the soil and regolith. - It is unweathered and forms the foundation of the Earth's surface. - Geological formations such as mountains and cliffs are often made up of exposed bedrock. SOIL HORIZONS - process of soil formation generally involves the downward movement of clay, water, and dissolved ions, and a common result of that is the development of chemically and texturally different layers 10  EROSION - physical removal and transportation of weathered material by water, wind, ice, or gravity - Mass wasting - also called gravitational erosion, is the transfer or movement of rock or soil down slope primarily by gravity 1. Fluvial Erosion (Water) 2. Aeolian Erosion (Wind) 3. Glacial and Periglacial Erosion (Ice) 4. Gravitational Erosion (Mass Wasting) a. Rock falls b. Landslides c. Debris/mud flows d. Slumps e. Creep DEPOSITION - process by which weathered and eroded materials are laid down or placed in a location that is different from their source DEPOSITIONAL ENVIRONMENTS - refers to the location where sediments are deposited (e.g., rivers, lakes, bottom of deep oceans…). - greatly influences the characteristics of sedimentary rocks, including their lithology, minerals, texture, sedimentary structures, and fossils KEYS to IDENTIFICATION of DEPOSITIONAL ENVIRONMENTS 1. Lithology - a combination of the mineral content and sedimentary texture of the rock 2. Sedimentary Structures - useful for determining which way was up in the original sequence of sediments especially if looking at beds of sediment that have been tilted to high angles, far from their original horizontal position 3. Fossils - remains or traces of biological organisms preserved in rocks commonly found in sedimentary rocks TYPES of DEPOSITIONAL ENVIRONMENTS 1. Continental/Terrestrial 2. Marginal Marine/Transitional 3. Marine FACTORS affecting SOIL FORMATION (Nature of Soils and Rate of Soil Formation (CLORPT)) 1. CL - climate 2. O - Organic Matter 3. R - Relief/Topography 4. P - Parent Materials 5. T – Time AGGREGATION - is important for increasing stability against erosion, for maintaining porosity and soil water movement SOIL PROFILE 1. Color 2. Structure 3. Texture 11