Chapter 14. Geology
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2. Down-lift Geographic Motion
1. Up-lift Geographic Motion
⑴ Type 1. Atmospheric Erosion
① Mechanical Destructive Action
② Chemical Decomposition
③ Weathering and Soil Formation
○ Development of Soil : The state of soil due to the actions of climate, reproduction, groundwater, etc.
○ Types of Soil Formation : Tundra Soil, Podzol, Gray Brown Forest Soil, Chernozems, Solontshak and Solonetz, Red Soil, Laterites, Prairie Soil, Tirs, Rendzina, Terra Rossa, Moor
○ Soil Profile : Initially categorized by Russian soil scientists using the A, B, C horizon system
○ Types of Soil : Original Soil, Transported Soil
⑵ Type 2. Erosion by Freshwater : Can be classified into surface water, subsurface water, groundwater, and lake water erosion
⑶ Type 2-1. Erosion by Surface Water
⑷ Type 2-2. Erosion by Subsurface Water
① Alluvial Fans and Alluvial Plains
② Streams
○ Outer Side of Streams : Active erosion due to higher kinetic energy
○ Inner Side of Streams : Slower flow with reduced transport capacity leading to deposition
○ Positive Feedback : Streams develop in the direction of greater curvature
③ Alluvial Plains
④ Floodplains
○ Cause : Intense deposition due to reduced flow velocity
○ Differences in Triangle Diagrams, Classifications, and Source Materials
⑤ Delta and Alluvial Fans
⑥ River Mouths
⑦ Cyclic Nature of Erosion
○ Young Terrain
○ Mature Terrain
○ Old Terrain
⑸ Type 2-3. Erosion by Groundwater
⑹ Type 2-4. Erosion by Lakes
⑺ Type 3. Erosion by Seawater
① Destructive Action of Seawater
② Constructional Action of Seawater
⑻ Type 4. Erosion by Glaciers (Glacial Erosion)
① Types of Glaciers
○ Local Glaciers : Valley Glaciers, Alpine Glaciers, also known as Alpine-Style Glaciers
○ Continental Glaciers (Antarctica) : Begin moving outward from a central point
○ Ice Sheet, Ice Cap : Cover a substantial land area with an ice thickness facing downwards
○ Piedmont Glaciers : Valley glaciers that merge and expand at the foot of mountains, like in Alaska
② Flow Velocity and Size of Glaciers
③ Glacial Landforms
○ Cirque
○ Hanging Valley
○ Glacial Lake
○ Fjord
○ Moraine
④ Transport and Depositional Action of Glaciers
⑼ Type 5. Erosion by Organisms
① Destructive Action
② Constructional Action
2. Down-lift Geographic Motion
⑴ Regulation Movement
① Evidence of Melting Movement : Melt Pits, Coastal Erosion, Parallel Discordances, Shell Holes on the Pillars of Serapis Temple
② Evidence of Subsidence Movement : Subsidence Coast
⑵ Orogenic Movement and Moisture-Curve Monolayer
① Moisture-Curve : Rock layers bending due to lateral pressure on strata
○ Anticline : Upward-convex moisture-curve
○ Syncline : Downward-concave moisture-curve
② Types of Moisture-Curves
○ Normal Folding
○ Inclinal Folding
○ Isoclinal Folding
○ Recumbent Folding
○ Fan-Shaped Folding
○ Dome-Shaped Folding
○ Centroclinal Folding
③ Fault
○ Hanging Wall : Upper portion relative to the fault plane
○ Footwall : Lower portion relative to the fault plane
○ Normal Fault : Hanging wall is below footwall, caused by tension
○ Reverse Fault : Hanging wall is above footwall, caused by compression
④ Fault Movement
○ Step Fault
○ Splintered Fault
○ Tilted Block
○ Overthrust Fault
⑶ Orogenic Periods and Arrangement of Mountain Ranges
① Arrangement of Mountain Ranges
○ Anticlinal Valleys
○ Chains
⑷ Volcanic Phenomena
① Principles of Volcanic Activity
② Gains and Losses from Volcanic Activity
⑸ Earthquakes
① Overview
○ Seismic Intensity : Measures earthquake damage
○ Magnitude : Measures energy released during an earthquake
② Causes of Earthquakes
○ Fault Origin Hypothesis
○ Igneous Origin Hypothesis
③ Earthquake Weather
④ Changes in Terrain due to Earthquakes
⑹ Stratigraphic Principles of Geology
① Principle of Uniform Processes
○ Proposed by James Hutton
○ Claims Earth’s history is longer than the 6,000 years suggested by the Bible
② Principle of Superposition
③ Principle of Biological Evolution
④ Principle of Inclusion
⑤ Principle of Disconformity
⑺ Interpretation of Strata
① Conformity and Disconformity
○ Conformity : Layer with continuous deposition
○ Disconformity : Layer with signs of halted deposition for a considerable period
○ Parallel Disconformity : Layers above and below appear parallel, like conformity
○ Angular Disconformity : Layers above and below meet at an angle due to uplift
○ Discordant Intrusion : Intrusion in disconformity plane, observed in angular disconformity
○ Unconformity : Layer eroded due to disconformity
② Dip and Strike : (Note) Original layers deposited horizontally but tilted due to tectonic movements
○ Strike : Intersection line between
strata and horizontal plane
○ Dip : Angle between strike and the bedding plane of a rock layer. 0° ≤ θ ≤ 90°
○ Symbols for Strike and Dip on Maps
○ Strike represented as ‘ㅜ’, dip as a short line
○ Example of Strike : N30°E
○ Example of Dip : 25°SE = 25°NW
○ Horizontal layers represented as ⊕
○ Clinometer
Figure 1. Clinometer
○ Strike : Represents the direction of true north.
○ Dip : Represents the direction of gravity.
○ Bubble in the spirit level : Indicates horizontality when located at the center. Should be centered when measuring strike.
○ Measurement of strike : Long side of the clinometer should be parallel to the strike line. The outer number indicated by the needle represents the strike.
○ Measurement of dip angle : Long side of the clinometer should be parallel to the bedding plane. The inner number indicated by the dip needle represents the dip angle.
○ Measurement of dip direction : Measure strike using the direction of the dip needle.
③ Interpretation
○ Horizontal intrusion : When lava intrudes parallel to the surface.
○ Dyke : When lava intrudes vertically to the surface.
○ Fault : A specific part of the ground rising. Occurs along with intrusion.
○ (Note) Extrusive features are not related to intrusion.
④ Submarine Basaltic Ridge : Observed in the deep ocean.
⑤ Submarine Volcanic Ridge : Observed in shallow seas.
Figure. 2. Submarine Volcanic Ridge[Note:1]
○ Definition : Layered structure formed by irregular sedimentation due to flowing water, wind, etc.
○ Formed in shallower depths or basins.
○ Indicates wind or water direction during deposition of layers.
○ Well represented in volcanic rocks.
○ Not observable in bedding planes.
⑥ Erosion : Traces of flowing water. Observed in shallow seas.
Figure. 3. Erosion[Note:2]
○ Observable in bedding planes.
⑦ Desiccation : Marks of ground splitting due to drying. Observed in dry climates.
⑧ Cross-section and Three-dimensional Model of Geological Structures
Figure. 4. Cross-section and Three-dimensional Model of Geological Structures[Note:3]
3. Plate Tectonics
⑴ Evidence of Continental Drift Proposed by Wegener
① Continuity of geological structures observed across the Atlantic Ocean.
② Identical plant fossils found on various continents.
③ Traces of Ice Age glaciers in tropical regions.
④ Matching coastlines of South America and Africa.
⑤ (Note) Later, inconsistencies in the path of movement were discovered in paleomagnetic studies and became accepted as the theory.
⑥ (Note) The peninsula landmasses during the Ice Age were located between the southern peninsula and the equator.
⑵ Driving Forces of Plate Motion
① Factor 1: Mantle convection
② Factor 2: Slab pull
○ Plates are denser as they are subducted.
○ Result: Plates are dragged upwards due to tension.
③ Factor 3: Slab suction
○ Slabs detach and rapidly descend during subduction.
○ Result: Intensification of mantle convection, subduction of plates.
④ Factor 4: Ridge push
○ Ridges push plates away with gravitational slopes.
⑶ Major Plates and Boundaries
Figure. 5. Major Plates and Boundaries[Note:4]
① Continental Plate
② Oceanic Plate
⑷ Divergent Boundary (E) : Oceanic Plate - Oceanic Plate
① Characteristic 1: Trenchless earthquakes due to the absence of subducted plates.
② Characteristic 2: Tholeiitic magma. Active volcanic activity.
○ Tholeiitic magma is generated deeper and contains more iron.
○ Mostly tholeiitic magma in divergent boundaries.
③ Characteristic 3: Formation of oceanic lithosphere at divergent boundaries.
○ Thickness of the plate increases as moving away from rift.
○ Heat flow decreases as moving away from rift, representing the rise of mantle convection.
○ Depth increases as moving away from rift.
○ Age of oceanic lithosphere increases as moving away from rift.
○ Sediments on the ocean floor increase as moving away from rift.
④ Terrain : Mid-ocean Ridge (e.g., Mid-Atlantic Ridge, East Pacific Rise)
⑸ Divergent Boundary (A) : Continental Plate - Continental Plate
① Characteristic 1: Tholeiitic magma.
○ Tholeiitic magma is generated deeper and contains more iron.
○ Mostly tholeiitic magma in divergent boundaries.
② Characteristic 2: Formation of rift valleys.
② Terrain : Rift valley (e.g., East African Rift)
③ Divergent boundaries are mainly observed in oceanic plates.
○ Heat flow from mantle convection concentrates mainly in oceanic plates.
○ Continental plates act as insulators and do not focus heat flow.
○ Heat flow in continental plates is transferred by radioactive elements.
⑹ Convergent Boundary : Oceanic Plate - Oceanic Plate
① Characteristic 1: Shallow and deep earthquakes.
○ Shallow earthquakes occur together with deep earthquakes.
○ Due to subduction of denser oceanic plates, deep earthquakes occur.
② Characteristic 2: Tholeiitic or andesitic magma.
○ Tholeiitic magma when both subduct and generate magma at greater depths, containing more iron.
○ Andesitic magma when one oceanic plate is pushed upwards.
③ Characteristic 3: Volcanic arcs.
○ Volcanic Arcs: Chains of islands formed by volcanic activity about 100-400 km away from subduction zones towards the continent.
○ Volcanic arcs are the most representative structures at convergent boundaries between oceanic plates.
○ Andesitic magma is observed in volcanic arcs or subduction zones, while tholeiitic magma is observed beneath volcanic arcs.
○ Volcanic arcs are also called volcanic chains or island arcs.
④ Characteristic 4: Increase in density at the convergent boundary.
○ Denser oceanic lithosphere reaches the mantle faster and sinks beneath it.
○ Hydrous minerals with abundant hydroxyl groups (OH groups) lower melting points and increase volatility.
⑺ Convergent Boundary : Oceanic Plate - Continental Plate
① Characteristic 1: Shallow and deep earthquakes.
○ Shallow earthquakes occur together with deep earthquakes.
② Characteristic 2: Andesitic magma.
○ Andesitic magma is generated at shallower depths and contains less iron.
○ Produced due to the subduction of oceanic plates pushing the continental plate upwards.
③ Characteristic 3: Almost always involves subduction of oceanic plates : Due to higher density of oceanic plates.
④ Characteristic 4: Volcanic Arcs : Volcanic arcs develop at the convergent boundary between oceanic and continental plates.
Figure. 6. Formation of Volcanic Arcs at Oceanic-Continental Plate Boundary[Note:5]
⑤ Terrain : Andes Mountains, Nazca Plate - South American Plate
○ The continental landmasses are well developed on the eastern side of South America where no trench develops.
⑻ Convergent Boundary : Continental Plate - Continental Plate (B)
① Characteristic 1: Trenchless earthquakes due to the absence of subducted plates.
② Characteristic 2: No magma formation.
○ Reason: No subduction of continental plates.
○ No pathway for magma to escape.
○ Granitic magma intrusion can occur.
③ Characteristic 3: Thrust faulting with the involvement of the principal stress direction.
○ (Note) Transformation fault : Mainly generated at trenches. Formed due to differences in speed.
④ Terrain : San Andreas Fault, Transform Fault
⑼ Transform Boundary (D)
① Characteristic 1: Trenchless earthquakes due to the absence of subducted plates.
② Characteristic 2: No volcanic activity : No chance for magma to emerge.
③ Characteristic 3: Shear stress involved in the movement of the principal stress.
○ (Note) Conversion fault : Primarily generated at ridges. Formed due to differences in speed.
④ Terrain : San Andreas Fault, Conversion Fault
Input : 2019.04.07 12:11