Geophysics & Environmental Physics — 60 Terms Defined

Adiabatic Lapse Rate Geophysics & Environmental Physics °C/km or K/km The rate at which the temperature of a rising or descending air parcel changes as it expands or compresses adiabatically without heat exchange with surroundings. Dry: Γ_d = g / c_p ≈ 9.8 °C/km; Moist: Γ_m ≈ 4–7 °C/km

Albedo Geophysics & Environmental Physics Dimensionless Fraction (0.0 to 1.0) The fraction of total incident solar electromagnetic radiation reflected back into space by a surface or planetary body. α = Reflected Solar Irradiance / Total Incident Solar Irradiance

Asthenosphere Geophysics & Environmental Physics Pa·s (Mantle Viscosity ~10¹⁹–10²¹ Pa·s) The ductile, mechanically weak, deformable upper mantle layer located directly beneath the rigid lithosphere. Seismic Low-Velocity Zone (LVZ): Depth ~ 100–250 km

Atmospheric Aerosols Geophysics & Environmental Physics μg/m³ (Concentration) Microscopic solid particles or liquid droplets suspended in the atmosphere originating from natural or human sources. Aerosol Optical Depth (AOD) τ, Direct/Indirect Radiative Effect

Auroral Oval Geophysics & Environmental Physics Degrees Latitude (~60°–70° Geomagnetic Latitude) An elliptical ring-shaped belt around Earth's magnetic poles where energetic magnetospheric electrons precipitate into the upper atmosphere to create auroras. Excitation: e⁻ + O → O* → O + h ν (557.7 nm Green Light)

Chandler Wobble Geophysics & Environmental Physics Arcseconds or Meters at Surface A small periodic nutation wobble of Earth's rotational axis relative to its solid crust with a period of ~433 days. Period T ≈ 433 days, Amplitude ~ 3–15 meters

Continental Drift Geophysics & Environmental Physics Geologic Time Scale (Millions of Years) The historical hypothesis proposed by Alfred Wegener in 1912 stating that Earth's continents were once joined in a single supercontinent (Pangea) before drifting apart. Historical Wegener Hypothesis (Pangea Supercontinent)

Cryosphere Geophysics & Environmental Physics km² (Spatial Extent) or Gt (Mass) The collective portion of Earth's surface where water exists in solid frozen form. Components: Sea Ice, Glaciers, Ice Sheets, Permafrost, Snow Cover

Darcy's Law Geophysics & Environmental Physics m/s (Darcy Flux q) A foundational hydrogeological equation describing the flow rate of fluid through a porous medium under a hydraulic gradient. Q = -K A (dh / dl), q = Q / A = -K ∇h

Dendrochronology Geophysics & Environmental Physics Annual Calendar Years The scientific discipline of dating annual tree rings to reconstruct past local climate conditions and calendar dates. Tree Ring Width w = f(Temperature, Precipitation, Soil Moisture)

Earth's Energy Budget Geophysics & Environmental Physics W/m² (Watts per square meter) The precise balance between incoming solar radiation absorbed by Earth and outgoing thermal infrared radiation emitted back into space. F_solar (340 W/m²) = F_reflected (100 W/m²) + F_emitted_IR (240 W/m²)

Earth's Inner Core Geophysics & Environmental Physics GPa (Pressure) & Kelvin (~5700 K) The solid, innermost spherical core of Earth composed primarily of a crystallized iron-nickel alloy at intense pressure. Radius R ≈ 1220 km, Pressure P ≈ 330–360 GPa

Earth's Outer Core Geophysics & Environmental Physics Pa·s (Liquid Viscosity ~10⁻³ Pa·s) The fluid interior layer of Earth ~2,260 km thick composed of liquid iron-nickel alloy surrounding the solid inner core. Radius ~ 3480 km to 1220 km (Liquid Iron-Nickel Alloy)

Geoid Geophysics & Environmental Physics Meters (Geoid Undulation Height) The hypothetical shape of Earth's surface defined by an equipotential surface of Earth's gravity field matching mean ocean sea level in the absence of tides and winds. Equipotential Surface V_gravity = Constant

Geomagnetic Reversal Geophysics & Environmental Physics Geologic Time Interval A major planetary event during which Earth's magnetic field undergoes a complete polarity flip, swapping magnetic North and South poles. Reversal Interval ~ 200,000 to 300,000 years

Geomagnetic Storm Geophysics & Environmental Physics nT (Nanoteslas, Dst / Kp Index) A major temporary disturbance of Earth's magnetosphere caused by solar wind shockwaves or Coronal Mass Ejections (CMEs). Dst Index < -50 nT (Distortion of Equatorial Ring Current)

Geomagnetism Geophysics & Environmental Physics μT (Microteslas, ~30–60 μT at surface) The scientific study of Earth's magnetic field, its internal origin in the liquid outer core, spatial variations, and temporal fluctuations. B_geo = ∇ × A (Geodynamo Induction: ∂B/∂t = ∇ × (v × B) + η ∇²B)

Geostrophic Wind Geophysics & Environmental Physics m/s (Wind Velocity) A theoretical atmospheric wind resulting from a exact balance between the horizontal Pressure Gradient Force and the Coriolis acceleration force. v_g = (1 / (2 ρ Ω sin φ)) (dP / dn) = (1 / f ρ) ∇P

Geothermal Gradient Geophysics & Environmental Physics °C/km or K/km The rate at which Earth's interior temperature increases with increasing depth below the surface. q = -k (dT / dz) (Heat Flux = Conductivity × Gradient)

Glaciology Geophysics & Environmental Physics m/year (Glacier Flow Velocity) The scientific study of glaciers, ice sheets, snow, and all natural ice phenomena in the cryosphere. Glen's Flow Law: ε̇ = A τ^n (Non-linear ice creep)

Gravimetry Geophysics & Environmental Physics mGal (Milligals = 10⁻⁵ m/s²) The precise measurement of spatial and temporal variations in Earth's gravitational acceleration field. g_observed = g_theoretical + Δg_FreeAir - Δg_Bouguer + Δg_Terrain

Greenhouse Effect Geophysics & Environmental Physics °C or Kelvin (Warming Effect) The thermodynamic warming process by which atmospheric greenhouse gases absorb outgoing infrared terrestrial radiation and re-emit it in all directions, raising surface temperatures. T_surface = T_effective (1 + ¾ τ_IR)^(1/4) (Radiative Equilibrium)

Gutenberg Discontinuity Geophysics & Environmental Physics km (Boundary Depth) The major geophysical boundary located at a depth of ~2,890 km marking the sharp transition between Earth's solid mantle and liquid outer core. Depth z ≈ 2890 km (Core-Mantle Boundary D'' Layer)

Hydrologic Cycle Geophysics & Environmental Physics Global Water Flux (km³/year) The continuous global movement and transformation of water through Earth's atmosphere, land surface, oceans, and subsurface aquifers. Water Balance: P = E + R + ΔS (Precipitation = Evaporation + Runoff + Storage Change)