Unit 4: Earth Systems and Resources Study Notes

Unit 4: Earth Systems and Resources - Exhaustive Study Notes

Topic 4.1: Plate Tectonics and Earth's Structure

• Composition of Earth's Core     * The core is a dense ball composed of nickel and iron.     * It contains radioactive elements that undergo decay, releasing a tremendous amount of heat.

• The Mantle and Lithosphere     * The mantle is a molten magma sea kept in a liquid state by the heat from the core.     * Tectonic plates are huge slabs of rock, also known as the lithosphere, that float on top of the mantle.

• Plate Boundaries and Landforms     * Divergent Boundaries:         * Plates move away from each other due to rising magma from a hot portion of the mantle.         * This process, typically occurring between oceanic plates, is called seafloor spreading.         * Features formed include mid-oceanic ridges and underwater trenches.     * Convergent Boundaries:         * Plates collide with one another.         * Subduction: When an oceanic plate and a continental plate collide, the more dense oceanic plate is forced beneath the continental plate.         * Consequences of Subduction: Magma is forced up through the lithosphere, leading to the formation of volcanic mountain ranges along the coast.         * Trenches often form at the exact point where one plate slides beneath the other.     * Transform Plate Boundaries (Transform Faults):         * Plates slide past each other in opposite directions.         * Earthquakes: Occur because plates get "stuck" or "locked" while trying to move. When the force of the underlying magma overcomes the friction at the locked fault, they slide instantly, releasing energy through the surface.

Topic 4.2 & 4.3: Soil Formation and Properties

• Defining Soil vs. Dirt     * Soil is a complex mixture of weathered rock particles (sand, silt, and clay) and organic material.     * Organic Content: Includes living microbes (decomposers) and non-living matter (decomposing leaves and animal waste).     * Pore Space: Empty spaces within the soil that allow oxygen and water to reach plant roots.

• Soil Formation and Weathering     * Parent Material: The original rocks that break down to form the inorganic/mineral components of soil.     * Weathering: The breakdown of rocks into smaller pieces through mechanical forces like rain and the freeze-thaw cycle of water.     * Erosion: The movement of rock pieces by wind and rain. This is a natural process but can be worsened by human activity.         * Impact of Erosion: Removes topsoil, along with vital nutrients, microorganisms, and bacteria necessary for plant growth.

• Earth's Soil Horizons (Layers)     * O Horizon: The top layer filled with organic material, decomposers, plant roots, and partially decomposed biomass (e.g., Dead Leaves).     * A Horizon (Topsoil): A critical layer containing both organic matter and mineral components ($N$, $P$), oxygen, and water.     * B Horizon (Subsoil): Contains very little organic material but still holds nutrients for growth.     * C Horizon: Deepest layer containing parent material that has undergone very little weathering.

• Soil as a Filtration System     * Rainwater seeps down (infiltrates) through pore spaces. Soil acts as a filter, trapping pollutants and allowing clean water to recharge aquifers.

• Physical Properties: Soil Texture     * Determined by the percentage of sand, silt, and clay.     * Particle Sizes: Sand is the largest, followed by silt, and clay is the smallest.     * Permeability: The ease or speed with which water moves through soil.         * Larger particles (sand) create larger pores, leading to high permeability.         * Smaller particles (clay) pack together tightly, leading to low permeability.     * Water Holding Capacity: The opposite of permeability. Soils with high permeability (sand) have low water holding capacity.     * Goldilocks Level: Most plants prefer intermediate pore sizes (Loam). Too much clay can drown roots by preventing oxygen access; too much sand lets water drain too fast for roots to absorb it.

• Soil Texture Triangle Example     * A sample with $20\%$ clay, $35\%$ silt, and $45\%$ sand is classified as a Loam.     * Other classifications include silty loams or sandy loams.

• Chemical Properties     * Soil PH: A measure of acidity ($H^+$ ion concentration). Low pH signifies high acidity.         * Nutrient Leaching: $H^+$ ions can leach nutrients like nitrogen or calcium out of the soil.         * Toxic Metals: Acidic soil makes metals like aluminum ($Al$) more soluble, allowing them to enter and damage plant roots.     * Nutrients: Nitrogen ($N$) and Phosphorus ($P$) are the primary limiting factors for plant growth.     * Soil Fertility: The overall ability to support plant growth, influenced by high nutrients and optimal pH.

Topic 4.4: Earth's Atmosphere

• Composition of the Atmosphere     * Nitrogen ($N_2$): approx. $78\%$ (not biologically available until fixation into ammonia).     * Oxygen ($O_2$): approx. $21\%$     * Argon ($Ar$): approx. $1\%$     * Trace Gases (including $CO_2$ and $CH_4$): approx. $0.4\%$     * Note: Greenhouse gases represent a tiny fraction but can dramatically alter climate due to heat-trapping abilities.

• Atmospheric Layers (Temperature/Altitude Relationships)     * Troposphere: Closest to Earth. Site of weather and breathable air. Gets colder as altitude increases.     * Stratosphere: Second layer. Contains the Ozone Layer, which absorbs $UVB$ and $UVC$ radiation (preventing cancer/cataracts).     * Mesosphere: Middle layer; gas molecules become less dense.     * Thermosphere: Hottest layer due to direct solar radiation. Site of the Aurora Borealis (Northern Lights), caused by solar wind particles colliding with $N$ and $O$.     * Exosphere: Outermost layer merging with space.

Topic 4.5: Global Wind Patterns

• Fundamental Properties of Air     1. Warm air holds more moisture than cold air.     2. Warm air rises.     3. Rising air experiences less pressure and cools.     4. Water vapor condenses as air cools.

• Hadley Cell Circulation     * At the Equator ($0^\circ$), direct sunlight heats air, causing it to rise and drop heavy rain (low pressure).     * The air spreads out and sinks at $30^\circ$ North and South.     * Sinking air is dry, creating deserts and high-pressure conditions.

• Coriolis Effect and Trade Winds     * Air moves from high pressure ($30^\circ$) to low pressure ($0^\circ$).     * Earth spins West to East at nearly $1,000\,mph$ at the equator.     * This causes the deflection of wind: Eastern Trade Winds (Easterlies) move East to West between $30^\circ$ and the Equator.     * Westerlies: Between $30^\circ$ and $60^\circ$, the Earth's surface moves slower (approx. $380\,mph$ slower than at $30^\circ$). This causes the air moving toward the poles to deflect with the spin (West to East).

Topic 4.6: Watersheds

• Definition: An area of land that drains into one central body of water (visualized as a giant land funnel).
• Key Characteristics:     * Slope: Topography determines where water drains; ridges separate different watersheds. Steeper slopes increase runoff and decrease infiltration.     * Vegetation/Soil: More plants and permeable soil lead to better groundwater infiltration and pollutant filtration.
• Human Impact (Urbanization): Pavement and impermeable surfaces cause rainwater to become runoff, carrying pollutants like sediment, plastic, motor oil, and fertilizer into rivers.

Topic 4.7: Solar Radiation and Seasons

• Insolation: Amount of solar radiation reaching an area, measured in Watts per meter squared ($W/m^2$).

• Variations in Insolation:     1. Curvature: Equator receives perpendicular (direct) rays, concentrating energy. Higher latitudes receive oblique (angled) rays, spreading energy over larger areas.     2. Atmosphere: Rays travel through more atmosphere at higher latitudes, causing more scattering.

• The Seasons     * Caused by Earth's tilt ($23.5^\circ$), not distance from the sun.     * June Solstice (June 21): Northern Hemisphere tilted toward the sun; summer. Sun rays most direct at Tropic of Cancer ($23.5^\circ\,N$). Longest day in North.     * December Solstice (December 21): Northern Hemisphere tilted away; winter. Sun rays most direct at Tropic of Capricorn ($23.5^\circ\,S$).     * Equinoxes (September and March): Earth positioned parallel to the sun. Equal day length and insulation in both hemispheres. Sunlight direct at Equator.

Topic 4.8: Geography and Climate

• Lake Effect Snow: Prevailing winds pick up moisture moving across large bodies of water (e.g., Great Lakes). As the air mass hits land and cools, the moisture falls as heavy snow. In Michigan, snowfall tapers off from West to East as moisture is depleted.
• Rain Shadow Effect:     * Windward Side: Portion of mountain facing the wind. Air rises, cools, and drops precipitation, supporting forests.     * Leeward Side: Portion facing away from the wind. Air descending is very dry. This creates arid/desert conditions (e.g., Mojave Desert, Death Valley on the leeward side of Sierra Nevada).

Topic 4.9: El Nio Southern Oscillation (ENSO)

• Normal Conditions:     * Trade winds blow warm water East to West (toward Australia/SE Asia).     * Upwelling: Cold, nutrient-rich water rises off South America to replace warm water. This supports productive fisheries.     * Thermocline: Tilts East to West.

• El Nio Conditions:     * Trade winds weaken or reverse.     * Warm water pools near South America.     * Effects: Flooding/rain in South America; drought in Australia/SE Asia. Upwelling is suppressed, causing fisheries to suffer from lack of nutrients/oxygen.

• La Nia Conditions:     * Trade winds intensify East to West.     * Greater warm water accumulation in the West.     * Effects: Excessive rain/flooding in Australia/SE Asia; colder/drier conditions (drought) in South America. Extremely strong upwelling improves fisheries.

Questions & Discussion

• Question from student: "bruh Mr SME why do the arrows change direction from $30^\circ$ to $60^\circ$?"
• Response: It is due to the difference in surface rotation speed at different latitudes. Because the Earth has a larger circumference at $30^\circ$ than it does at $60^\circ$, the surface moves about $380\,mph$ faster at $30^\circ$. This causes air moving toward the pole to be deflected in the direction of earth's spin (West to East).