Geomorphic Processes PDF

**GEOMORPHIC PROCESSES** - the physical processes which create and modify *landforms* on the surface of the earth → can be *ENDOGENOUS (Endogenic)* vs. *EXOGENOUS (Exogenic)* processes → Involves the rock cycle **EXOGENOUS PROCESSES** *(GRADATIONAL)* - A geomorphic process that happens on the sur...

**GEOMORPHIC PROCESSES** - the physical processes which create and modify *landforms* on the surface of the earth → can be *ENDOGENOUS (Endogenic)* vs. *EXOGENOUS (Exogenic)* processes → Involves the rock cycle **EXOGENOUS PROCESSES** *(GRADATIONAL)* - A geomorphic process that happens on the surface of the Earth, and modify relief → they comprise ***degradation*** and ***aggradation*** they modify relief → these processes are carried through by Geomorphic Agents: gravity, flowing water (rivers), moving ice (glaciers), waves and tides (oceans and lakes), wind, plants, microorganisms, animals, and humans → a continuum of processes \[*weathering, mass wasting, erosion, transportation, deposition* +-----------------------------------+-----------------------------------+ | **DEGRADATION PROCESSES** | **AGGRADATION PROCESSES** | | | | | → *Denudation Processes* | → Deposition by river and streams | | | | | \- Weathering | a. Deposition - fluvial, | | | glacial, coastal | | \- Mass wasting | | | | | | \- Erosion and Transportation | | | | | | **EROSION** - earth materials are | | | worn away by natural forces | | | | | | → small kind of mass wasting and | | | has normal movement | | | | | | **TRANSPORTATION** - Process of | | | moving the resulting sediment | | | | | | **DEPOSITION** - eroded rocks and | | | sediments settle somewhere new | | +-----------------------------------+-----------------------------------+ **WEATHERING** - disintegration and decomposition of rocks in situ - no transportation involved → Produces **REGOLITH** - product of weathering; loose materials from rocks →involves the mechanical or physical disintegration and/or chemical decomposition that fragments rock masses into smaller components that amass on-site, before being moved by gravity or transported by other agents → The processes begin in microscopic spaces, cracks, joints, faults, fractures, lava vesicles and other rock cavities **[TYPES OF WEATHERING:]** **01 PHYSICAL OR MECHANICAL WEATHERING** -- Disintegration and decay of rocks via weather elements: high temperatures, extreme cold and freeze-thaw cycles → No change in chemical composition of rocks - **EXFOLIATION** - due to thermal - expansion/contraction and/or release of pressure when buried rocks are uplifted and exposed - e.g., Exfoliation Dome (Stone Mountain, GA) and Exfoliation Sheets (Sierra Nevada)  **02 CHEMICAL WEATHERING** - breakdown of rocks by chemical mechanisms → decomposes rocks through a chemical change in its minerals → ***Oxidation** -* important in iron-rich rocks - reddish coloration like rust → ***Hydrolysis*** - igneous rocks have much silica which readily combines with water → ***Carbonation and Salution*** - carbon dioxide dissolved in water reacts with carbonate rocks to create a soluble product (calcium bicarbonate) **03 BIOLOGICAL WEATHERING** - weakening and subsequent disintegration of rock by plants, animals and microbes  **MASS WASTING** - Downslope movement of rock, soil and other debris due to the pull of gravity → Factors affecting or inducing the event: - Speed - Type of material - Nature of movement - Water - Soil Cover - Geologic features **[FACTORS AFFECTING MASS WASTING]** **01 ANGLE OF REPOSE** - highest angle that the side/slope of a mound of unconsolidated sediments will achieve under the influence of gravity **02 WATER** - Moist sand will be able to achieve steeper sides (higher angle of repose) - the water is enough to fill in some spaces for additional surface tension, cohesion and adhesion which keeps the sediments together → Too much water, the grains will tend to slide past one another and become more fluid (lower angle) **03 SOIL COVER** - Soil is basically a mixture of rocks, regolith (weathered rock materials), organic matter, water and air → Expansion and contraction of soil containing clay minerals affect the stability and consolidation of the material potential for mass wasting → Because of expansion, intergranular contact may be decreased and it increases the susceptibility to a mass wasting event **04 GEOLOGIC FEATURES** - Presence of Structures and rock types → Structures: beddings, joints and faults → ***JOINTS AND FAULTS*** - provide additional conduits for water to pass through inner regions of rock mass → ***BEDDING PLANE*** - zone of weakness of a rock that may increase the potential of slide **05 TRIGGERING EVENTS** - Earthquakes → Excessive Rainfall → Volcanic Eruptions  +-----------------------------------------------------------------------+ | Distance travelled affects *Clast size, Clast shape, and Class | | sorting* | | | | → Farther from source means rounder and smaller | | | | → ***Steepness of slope*** - poorly sorted and angular | | | | → ***Strength of Current*** | | | | - Strong - large clasts | | | | - Weak - fine grained | | | | → ***Agent of Transport*** (water, wind or ice) | | | | - Wind - fine | | | | - Glaciers - large & small | +-----------------------------------------------------------------------+ **ENDOGENOUS PROCESSES** - a geomorphic process that often happens beneath the surface of the Earth, and create relief → are large - scale landform building and transforming processes **01 TECTONIC PROCESSES** - (Also called Diastrophism) a.Folding: anticlines (up), synclines (down), mountains b.Faulting: rift valleys, c.Lateral Faulting: strike slip faults **02 IGNEOUS PROCESSES** \- a. Volcanism: Volcanic eruptions Volcanoes b.Plutonism: Igneous intrusions - Earthquakes - evidence of present-day tectonic activity **MAGMA** - This comes form igneous rocks and some semi molten materials composed of molten rocks and minerals → A molten or semi-molten rock mixture found under the surface of the Earth. This mixture is usually made up of four parts: - a hot liquid base, called the melt; - minerals crystallized by the melt; - solid rocks incorporated into the melt from the surrounding confines; and - dissolved gases **[MAGMA FORMATION:]**  +-----------------------------------------------------------------------+ | **DECOMPRESSION MELTING** - Involves the upward movement of Earth\'s | | mostly solid mantle. | | | | → This hot material rises to an area of lower pressure through the | | process of ***CONVECTION*** | | | | → Areas of lower pressure always have a lower melting point than | | areas of high pressure. | | | | → This reduction in overlying pressure, or decompression, enables the | | mantle rock to melt and form magma. | | | | → often *[occurs at divergent boundaries]*, where | | tectonic plates separate. The rifting movement causes the buoyant | | magma below to rise and fill the space of lower pressure. The rock | | then cools into a new crust | | | | → Decompression melting also occurs at mantle plumes (hot spots), | | columns of hot rock that rise from Earth\'s high pressure core to its | | lower-pressure crust. | +-----------------------------------------------------------------------+ | **TRANSFER OF HEAT** - Magma can also be created when hot, liquid | | rock intrudes into Earth\'s cold crust. | | | | → As the liquid rock solidifies, it loses its heat to the surrounding | | crust. Much ike hot fudge being poured over cold ice cream, this | | transfer of heat is able to melt the surrounding rock (the \"ice | | cream\") into magna | | | | → Transfer of heat often happens at convergent boundaries, where | | tectonic plates are crashing together. | +-----------------------------------------------------------------------+ | **FLUX MELTING** - occurs when water or carbon dioxide are added to | | rock | | | | → These compounds cause the rock to melt at lower | | | | temperatures. This creates magma in places where it originally | | maintained a solid Structure. | | | | → Much like heat transfer, flux melting also occurs around subduction | | zoned | +-----------------------------------------------------------------------+ **PLUTONISM** - The formation of intrusive igneous rock by solidification of magma beneath the earth\'s surface → James Hutton (and others) - Plutonism Theory: rock forming processes are driven by heat contained within the interior of the Earth **VOLCANISM** - Any of various processes and phenomena associated with the surficial discharge of molten rock, pyroclastic fragments, or hot water and steam →eruption of molten rock (magma) onto the surface of a planet → Volcanoes are evidences of the internal heat that the earth can release unto the surface **METAMORPHISM** - Alteration of the composition or structure of a rock by heat, pressure, or other natural agency \- The process by which rocks are changed in composition, texture or structure by extreme heat and pressure +-----------------------------------------------------------------------+ | **[TYPES OF METAMORPHISM:]** | | | | **1. Contact Metamorphism** - due to proximity to igneous | | | | Intrusions | | | | **2. Cataclastic Metamorphism** - due to mechanical deformation (ie | | the sliding of rock material between faults) | | | | **3. Hydrothermal Metamorphism** - due to high temperatures and | | moderate pressures by hydrothermal fluids | | | | **4. Regional Metamorphism** - occurs in large areas and accompanied | | by deformations from non-hydrostatic or differential stress | | conditions | | | | **5. Burial Metamorphism** - due to temperatures reached when rock is | | buried to depths of several hundred meters | | | | **6. Shock/Impact Metamorphism** - due to stresses from the impact of | | extraterrestrial material or large volcanic eruptions | +-----------------------------------------------------------------------+