Geophysics & Environmental Physics

Adiabatic Lapse Rate

The rate at which the temperature of a rising or descending air parcel changes as it expands or compresses adiabatically without heat…

Dry: Γ_d = g / c_p ≈ 9.8 °C/km; Moist: Γ_m ≈ 4–7 °C/km °C/km or K/km

Albedo

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 Dimensionless Fraction (0.0 to 1.0)

Geophysics & Environmental Physics

Asthenosphere

The ductile, mechanically weak, deformable upper mantle layer located directly beneath the rigid lithosphere.

Seismic Low-Velocity Zone (LVZ): Depth ~ 100–250 km Pa·s (Mantle Viscosity ~10¹⁹–10²¹ Pa·s)

Geophysics & Environmental Physics

Atmospheric Aerosols

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 μg/m³ (Concentration)

Geophysics & Environmental Physics

Auroral Oval

An elliptical ring-shaped belt around Earth's magnetic poles where energetic magnetospheric electrons precipitate into the upper atmosphere…

Excitation: e⁻ + O → O* → O + h ν (557.7 nm Green Light) Degrees Latitude (~60°–70° Geomagnetic Latitude)

Geophysics & Environmental Physics

Chandler Wobble

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 Arcseconds or Meters at Surface

Geophysics & Environmental Physics

Continental Drift

The historical hypothesis proposed by Alfred Wegener in 1912 stating that Earth's continents were once joined in a single supercontinent…

Historical Wegener Hypothesis (Pangea Supercontinent) Geologic Time Scale (Millions of Years)

Geophysics & Environmental Physics

Cryosphere

The collective portion of Earth's surface where water exists in solid frozen form.

Components: Sea Ice, Glaciers, Ice Sheets, Permafrost, Snow Cover km² (Spatial Extent) or Gt (Mass)

Geophysics & Environmental Physics

Darcy's Law

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 m/s (Darcy Flux q)

Geophysics & Environmental Physics

Dendrochronology

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) Annual Calendar Years

Geophysics & Environmental Physics

Earth's Energy Budget

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) W/m² (Watts per square meter)

Geophysics & Environmental Physics

Earth's Inner Core

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 GPa (Pressure) & Kelvin (~5700 K)

Geophysics & Environmental Physics

Earth's Outer Core

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) Pa·s (Liquid Viscosity ~10⁻³ Pa·s)

Geophysics & Environmental Physics

Geoid

The hypothetical shape of Earth's surface defined by an equipotential surface of Earth's gravity field matching mean ocean sea level in the…

Equipotential Surface V_gravity = Constant Meters (Geoid Undulation Height)

Geophysics & Environmental Physics

Geomagnetic Reversal

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 Geologic Time Interval

Geophysics & Environmental Physics

Geomagnetic Storm

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) nT (Nanoteslas, Dst / Kp Index)

Geophysics & Environmental Physics

Geomagnetism

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) μT (Microteslas, ~30–60 μT at surface)

Geophysics & Environmental Physics

Geostrophic Wind

A theoretical atmospheric wind resulting from a exact balance between the horizontal Pressure Gradient Force and the Coriolis acceleration…

v_g = (1 / (2 ρ Ω sin φ)) (dP / dn) = (1 / f ρ) ∇P m/s (Wind Velocity)

Geophysics & Environmental Physics

Geothermal Gradient

The rate at which Earth's interior temperature increases with increasing depth below the surface.

q = -k (dT / dz) (Heat Flux = Conductivity × Gradient) °C/km or K/km

Geophysics & Environmental Physics

Glaciology

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) m/year (Glacier Flow Velocity)

Geophysics & Environmental Physics

Gravimetry

The precise measurement of spatial and temporal variations in Earth's gravitational acceleration field.

g_observed = g_theoretical + Δg_FreeAir - Δg_Bouguer + Δg_Terrain mGal (Milligals = 10⁻⁵ m/s²)

Geophysics & Environmental Physics

Greenhouse Effect

The thermodynamic warming process by which atmospheric greenhouse gases absorb outgoing infrared terrestrial radiation and re-emit it in…

T_surface = T_effective (1 + ¾ τ_IR)^(1/4) (Radiative Equilibrium) °C or Kelvin (Warming Effect)

Geophysics & Environmental Physics

Gutenberg Discontinuity

The major geophysical boundary located at a depth of ~2,890 km marking the sharp transition between Earth's solid mantle and liquid outer…

Depth z ≈ 2890 km (Core-Mantle Boundary D'' Layer) km (Boundary Depth)

Geophysics & Environmental Physics

Hydrologic Cycle

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) Global Water Flux (km³/year)