Chapter 9. Components of the Earth’s Environment
Recommended post : 【Earth Science】 Table of Contents for Earth Science
1. Overview
2. Atmosphere
3. Hydrosphere
4. Lithosphere
5. Biosphere
1. Overview
⑴ Earth System
① Types of Systems
○ Type 1. Isolated System : No movement of matter and energy
○ Type 2. Closed System : Movement of energy but no movement of matter
○ Type 3. Open System : Both movement of matter and energy exist
② Earth’s environment can be considered an open system
⑵ Components of the Earth’s Environment
① Each element constituting the Earth’s environment is independent and interacts with each other
② Components of the Earth’s environment: Atmosphere, Hydrosphere, Lithosphere, Biosphere
③ Interactions between components
Table 1. Interactions between Components of the Earth’s Environment
2. Atmosphere
⑴ Atmosphere
① Layer of atmosphere surrounding the Earth at about 1,000 km altitude
② Composed of troposphere, stratosphere, mesosphere, and thermosphere
③ Upper boundary of the atmosphere is not well-defined: Hydrogen is distributed up to about 10,000 km
⑵ Troposphere
① Extends from the surface to about 11 km
② Factors affecting tropospheric temperature are mainly terrestrial radiation
③ Temperature decreases as altitude increases due to decreasing terrestrial radiation, causing instability
④ Instability leads to vigorous convection movements in the atmosphere
⑤ Temperature lapse rate: 6.5 ℃ / km
⑥ Tropopause: Boundary between troposphere and stratosphere
○ Tropopause height increases with lower latitudes due to vigorous convection
○ Tropopause height is higher during summer than winter due to more active convection
○ Equator: 17.5 km
○ Mid-latitudes: 11.5 km
○ Polar regions: 7.5 km
⑶ Stratosphere
① Presence of ozone layer: 20 ~ 30 km, 2 ~ 8 ppm
② Ozone layer absorbs harmful ultraviolet radiation from the Sun
③ Temperature increases with altitude due to high absorption of UV radiation: Stable atmosphere
④ Stability leads to the absence of convection movements
⑤ Absence of convection creates a stable route for prolonged aircraft flight
⑷ Mesosphere
① Factors affecting mesospheric temperature are mainly terrestrial radiation
② Temperature decreases as altitude increases due to decreasing terrestrial radiation, causing instability
③ Instability leads to vigorous convection movements
④ Despite vigorous convection, lack of water vapor prevents weather phenomena
⑤ Coldest region in the atmosphere
⑥ Almost no oxygen
⑸ Thermosphere
① Very high altitudes, air density is extremely low, temperature varies significantly due to space heat sources
② Temperature increases with altitude due to proximity to the Sun
③ Large temperature variation due to direct absorption of solar energy, resulting in strong diurnal changes
④ Aurora occurs due to external radiation
N < C < … < He < H
⑹ Exosphere
① Spans from about 60 km to 500 km
② Overlaps with the stratosphere, mesosphere, and thermosphere
③ Air molecules ionized by X-rays and ultraviolet radiation from the Sun in this region
○ Ions and free electrons distributed in the atmosphere
○ Bohr atom model: Electrons absorb energy and are emitted, forming ions
④ Divided into D, E, and F layers based on electron density
Figure 1. Ionospheric Layers
○ D layer: About 60 km ~ 80 km, long-wave reflection, daytime
○ E layer: About 100 km ~ 120 km, medium-wave reflection
○ F1 layer: About 170 km ~ 230 km, short-wave reflection, daytime
○ F2 layer: About 200 km ~ 500 km, short-wave reflection
○ Daytime: E layer, F layers
○ Nighttime: D layer, E layer, F1 layer, F2 layer
④ Roles
○ Role 1: Blocks ground waves
○ Role 2: Blocks external waves, higher altitudes block more energy from outside
○ Long-distance communication medium
⑺ Homosphere: Within about 80 km. Gas is uniform due to convection and mixing interactions. Extends up to mesosphere
① Dry air
○ Air excluding water vapor
○ Nitrogen (78%): Essential element for plant growth (cf. nitrogen, phosphorus, potassium)
○ Oxygen (21%): Important element for respiration and combustion in plants and animals
○ Argon (0.9%)
○ Carbon dioxide (0.03%)
② Gases that vary with time and location
○ Water vapor
○ Main cause of weather changes
○ Important in Earth’s heat balance through heat energy transport
○ Carbon dioxide (CO2)
○ Decreases due to plant photosynthesis
○ Increases due to emissions from Earth’s interior, industrial and vehicle emissions, respiratory activity of organisms, oceanic carbonates
○ Controlled by oceans
○ Major contributor to global warming
○ Ozone
○ Concentrated around 20 ~ 30 km
○ Absorbs ultraviolet radiation
○ Methane (CH4)
○ Increases due to livestock grazing, microbial methane production in terrestrial environments
⑻ Heterosphere: Within about 80 km to 1,000 km. Gas is uneven due to sparse density and diffusion. Begins in thermosphere
① Distribution of gases in the atmosphere: Heavier gases lower, lighter gases higher
② Hydrogen at 1,000 km
③ Helium at 600 ~ 1,000 km
④ Oxygen at 300 ~ 600 km
⑤ Nitrogen at 200 ~ 300 km
⑼ Karman Line
① Boundary defined by physicist Theodore von Kármán between Earth’s atmosphere and outer space
② Defined at 100 km altitude: However, there are claims to lower it to 80 km
3. Hydrosphere
⑴ Components of the Hydrosphere
① Natural water = Seawater (97.22%) + Freshwater (2.78%)
② Components of freshwater
○ Freshwater = Glaciers and ice sheets (1.91%) + Groundwater (0.84%) + Others (0.03%)
○ Rainwater dissolves minerals on land, resulting in high CO32- and Ca2+ content
③ Components of seawater
○ Composition of salt
○ Weathering and erosion of rocks
○ Submarine volcanoes: Highest concentration of Cl- due to underwater volcanic eruptions
○ Absence of CO32- and Ca2+ in seawater compared to freshwater due to biological utilization
○ 6 major elements in seawater (by mass)
○ Chloride ions (Cl-) : 55.0%
○ Sodium ions (Na+) : 30.6%
○ Sulfate ions (SO42-) : 7.7%
○ Magnesium (Mg2+) : 3.7%
○ Calcium (Ca2+) : 1.2%
○ Potassium (K+) : 1.1%
○ Element distribution in seawater (molar concentration)
Table 2. Element Distribution in Seawater
○ Variation in salinity according to latitude
○ Equator: Precipitation > Evaporation, low salinity
○ Mid-latitudes: Evaporation > Precipitation, high salinity
○ Polar regions: Intense ice melting, low salinity
○ Salinity of South Korea’s seas
○ Yellow Sea has lower salinity than East Sea: Yellow Sea is surrounded by land and has characteristics of freshwater
○ Salinity is lower in summer than winter: High precipitation - evaporation ratio in summer
○ Law of Constant Proportions of Salinity
Table 3. Law of Constant Proportions of Salinity
○ Mechanism: Mixed over long periods
○ Ion residence time
Figure 2. Ion Residence Time
○ Useful minerals extracted from seawater: Salt, magnesium, bromine, etc.
○ Gases dissolved in seawater: Oxygen, carbon dioxide, nitrogen, essential for marine life survival
⑵ Vertical Structure of Seawater: Differentiated by water temperature changes with depth
Figure 3. Division of Oceanic Layers
① Mixed Layer: 50 m ~ 200 m
○ Defined by a constant temperature in the vertical structure
○ Influenced by solar energy and wind: Wind-induced mixing maintains constant temperature
○ Thickens in winter: Cooling of surface water due to density currents increases the thickness of the mixed layer
○ Thickest at mid-latitudes: Strongest winds at mid-latitudes (due to atmospheric circulation)
○ Low concentration of carbon dioxide due to photosynthesis
② Thermocline: 200 m ~ 1,000 m
○ Defined by a rapid decrease in water temperature with increasing depth
○ Influenced by solar energy and wind: Less influence by wind
○ Stable: Lower layer always colder than upper layer, preventing convection
③ Deep Layer: 1,000 m ~
○ Definition: Zone with almost no temperature change below the thermocline layer.
○ Solar energy influence: No, Wind influence: No
○ Consistent water temperature regardless of latitude or season: 2 ~ 4 ℃. Density is highest at 4 ℃, but maximum density temperature varies under high-pressure situations.
○ Very low water temperature. High density. Low salinity.
○ Increased dissolved oxygen concentration due to cold subsurface seawater at high latitudes.
⑶ Seafloor Topography
Figure. 4. Seafloor Topography
① Continental Shelf: Gentle slope with depth less than 200 m, near land.
○ Near the continent.
② Continental Slope: Extends seaward from the continental shelf.
○ Steep gradient.
○ Downwelling currents primarily occur here.
③ Trench: Deep trench with depth over 6,000 m.
④ Abyssal Plain: Broad, flat seafloor terrain at depths of about 3,000 m to 6,000 m.
⑤ Seamount: Underwater mountain rising from the ocean floor, pushed up by rock beneath.
○ Heat flux increases closer to seamount.
○ Thickness increases farther from seamount.
○ Over time, points on tectonic plates move away from seamount.
○ Thermoclines develop dominantly.
⑥ Volcanic Island: Island formed by accumulation of underwater volcanic eruptions.
⑦ Seaknoll: Conical peak rising from the ocean floor.
⑧ Guyot: Flattened top of a submerged volcanic peak due to erosion from waves.
⑨ Continental Rise: Gradual sloping area extending from the continental slope to the deep seafloor.
4. ** **Lithosphere (rock sphere)
⑴ Methods of Earth’s Interior Investigation: Include drilling, volcanic eruption analysis, seismic wave analysis, etc.
① Drilling Method
② Volcanic Eruption Analysis
③ Seismic Wave Analysis
○ Seismic Waves: Waves generated by earthquakes observed by seismometers.
○ Characteristic 1: Reflect or refract when encountering different materials during propagation.
○ Characteristic 2: Velocity varies based on material through which they pass.
○ Type 1: P-waves
○ Key Features: Primary waves. Speed of 5 ~ 8 km/s. Low amplitude and damage.
○ Passes through solids, liquids, and gases.
○ Wave direction aligns with propagation direction.
○ P-waves drastically decrease at the boundary between the upper mantle and the outer core.
○ Type 2: S-waves
○ Key Features: Shear waves. Speed of about 4 km/s. Greater amplitude and damage.
○ Passes only through solid materials.
○ Wave direction is perpendicular to propagation direction.
○ PS Time (Initial Motion Duration): Time difference between P-waves and S-waves’ arrival.
○ Type 3: L-waves
○ Key Features: Surface waves. Speed of about 3 km/s. High amplitude and destructive. Propagates only on the surface.
○ Both shear and longitudinal waves are present.
○ Category 1: Love Waves
○ Category 2: Rayleigh Waves
○ PS Interval: Measures epicentral or hypocentral distances.
Figure. 5. PS Interval and Travel Time Curve
○ Method to determine hypocenter and epicenter through three observatories
○ P: Epicenter
○ Radius of the circle equals hypocentral distance from each observatory
○ Distance between epicenter and hypocenter is half of HH’ length
Figure. 6. Method to determine hypocenter and epicenter through three observatories
Figure. 7. Enlarged view of observatory A from the above figure
Point O is where the origin (hypocenter) is located, descending vertically by a length of OP or OP’.
○ Time-Distance Curve (Travel-Time Curve) for P-waves describes central P-wave.
Figure. 8. P-wave Time-Distance Curve
a represents direct wave, b represents refracted wave, bending point is the cross-over distance
Figure. 9. Refracted Wave and Direct Wave
○ Direct Wave: Time taken by direct seismic wave to travel from the epicenter S to observation point D.
○ Refracted Wave: Time taken by seismic wave to reach point D after being refracted at the crust-mantle interface.
○ Reflected Wave: Always arrives later than direct wave.
○ Cross-Over Distance: Distance to the point where direct and refracted waves meet. Proportional to the thickness of the crust.
○ If the hypocentral distance ℓ is short, the shorter distance covered by the direct wave causes it to arrive faster at D.
○ If the hypocentral distance ℓ is long, the difference in travel distances is minimal. Depending on density differences, faster refracted waves arrive at D.
○ Inference 1: Mantle’s P-wave velocity is faster than crustal velocity, as seismic waves refract.
○ Inference 2: Thicker crust results in a longer bending distance in the travel-time curve. With increased distance of the refracted wave, the time taken for it to reach the observation point is delayed.
○ Useful Formulas
④ Estimation Methods for Earth’s Internal Materials
○ Investigate seismic wave velocity distribution in Earth’s interior.
○ High-temperature, high-pressure experiments.
○ Chemical analysis of meteorites.
⑵ Earth’s Layered Structure
① Overview
○ Distinguishable through changes in seismic wave velocities.
○ Pressure and temperature increase with depth.
○ Density: Crust ＜ Mantle ＜ Outer Core ＜ Inner Core
○ Gravitational Acceleration: Highest at mantle’s boundary, decreases towards the center.
Figure. 10. Changes in Gravitational Acceleration with Depth[Note:8]
① Crust: Surface to Mohorovičić Discontinuity
○ Mohorovičić Discontinuity (Moho Discontinuity): 0 km to 100 km.
○ Discovered through refraction of nearby travel-time curves.
○ Consists of 1% of Earth’s total volume, solid.
○ Continental Crust: 30 ~ 50 km, average 30 km, density 2.7 g/cm³.
○ Upper Part: Granite rocks (sial layer).
○ Lower Part: Basaltic rocks (sima layer).
○ Oceanic Crust: 6 ~ 8 km, average 6 km, density 3 g/cm³, composed of basaltic rocks (sima layer).
② Mantle: Moho Discontinuity to Gutenberg Discontinuity
○ Structure:
○ Gutenberg Discontinuity: 2,900 km. Highest gravitational effect.
○ Mantle = Upper Mantle + Transition Zone + Lower Mantle.
○ Upper Mantle (Moho to 400 km) = Lithosphere + Asthenosphere.
○ Transition Zone: Faster seismic waves due to phase transitions.
○ Lower Mantle (700 to 2,900 km).
○ Slab: Solid part comprising crust and upper mantle.
○ Asthenosphere: 100 to 400 km. Partially molten, varying seismic wave velocity. Drives plate movement.
○ Characteristics:
○ Constitutes about 82% of Earth’s volume, largest volume and mass inside Earth.
○ About 67% of Earth’s total mass.
○ Density: 3.3 g/cm³.
○ Composed mainly of peridotite rocks, ultramafic composition.
○ Seismic Waves:
○ Shadow Zone: Area where seismic waves don’t reach due to presence of the core.
○ P-wave Shadow Zone: Seismic angle of 103 ~ 142°.
○ S-wave Shadow Zone: Seismic angle of 103 ~ 180°.
○ Low-Velocity Layer: Slows seismic waves in the upper mantle.
③ Outer Core: Gutenberg Discontinuity to Lehmann Discontinuity
○ Lehmann Discontinuity (Lehmann Discontinuity): 5,100 km.
○ Liquid state suggested due to presence of S-wave shadow zone.
○ Composed mainly of iron and nickel.
○ Highest rate of pressure increase within the Earth.
④ Inner Core: Lehmann Discontinuity to Earth’s center (6,400 km).
○ Presence of weak P-waves near a seismic angle of 110° suggests its existence.
○ Solid state inferred from increasing P-wave velocity.
○ Mainly composed of iron with some nickel.
⑶ Composition of Earth’s Crustal Materials
① Rocks Composing the Crust
○ Most common minerals in the crust are silicate minerals.
○ Near Surface Rocks: Sedimentary rocks (75%), igneous and metamorphic rocks (25%).
○ Rocks Near 16 km Below Ground: Sedimentary rocks (5%), igneous and metamorphic rocks (95%).
○ Upper Continental Crust: Granite rocks, rich in SiO2 and Al2O3 (sial layer), density 2.7 g/cm³.
○ Upper Part: Granitic rocks (sial layer).
○ Lower Part: Basaltic rocks (sima layer).
○ Lower Continental Crust, Oceanic Crust: Basaltic rocks, rich in SiO2 and MgO (sima layer), density 3.0 g/cm³.
② Eight Major Elements in the Crust (Mass Fraction)
○ O: 46.6%
○ Si: 27.7%
○ Al: 8.1%
○ Fe: 6.0%
○ Ca: 3.6%
○ Na: 2.8%
○ K: 2.6%
○ Mg: 2.1%
○ Mnemonic Tip: San Gu Al Cheol Na Cheol Ma
③ Clarke Number: Weight percentage of various elements present from sea level to about 16 km below ground.
⑷ Composition of Mantle Materials
① Closer to the crust than the core.
② Composed mainly of peridotite rocks containing pyroxene and olivine.
③ Rich in Fe and Mg, density between 3.3 to 5.5 g/cm³.
⑸ Composition of Core Materials
① Outer Core: Mixture of Fe including Ni (liquid state), density around 11 g/cm³.
② Inner Core: Mixture of Fe including Ni (solid state), density around 16.5 g/cm³.
5. ** **Biosphere
⑴ All living organisms on Earth and organic materials that haven’t decomposed yet.
⑵ Inhabit surface, internal soil, oceans, and subsurface of atmosphere (below about 8 km altitude).
⑶ Plays a crucial role in altering Earth’s atmospheric composition and surface.
Input : 2019.08.16 22:49