Earth science
Rocks and plate tectonics
Rock cycle, earthquakes, volcanoes, plate boundaries.
Basics
Rock cycle
Igneous: cooled magma. Sedimentary: particles, precipitation, compaction. Metamorphic: recrystallized by heat and pressure. Weathering, erosion, and melting link them.
Plate tectonics
Lithospheric plates move over the asthenosphere. Divergent: rifts and ridges, new crust. Convergent: subduction or collision mountains. Transform: side-by-side slip. Most quakes and volcanoes hug boundaries.
Earthquakes
Elastic rebound: a fault slips. P waves (compressional, faster) then S waves (shear, not through liquid) then surface waves (most damage). Focus is inside; epicenter is above it.
Formulas
Density
Crust is lighter than mantle; oceanic (basaltic) crust is denser than continental (granitic) crust.
Symbols
-
ρdensity -
mmass -
Vvolume
Moment magnitude (idea)
Uses rigidity, fault area, and slip. Better than Richter for large events.
Symbols
-
μrigidity -
Afault area -
Daverage slip
Key table
| Crust | Continental ~30–70 km, oceanic ~5–10 km |
|---|---|
| Age of Earth | about 4.54 billion years |
| Outer core | Liquid Fe–Ni — S-wave shadow, geodynamo |
In this field
Atmosphere and weather
Layers, wind, clouds, fronts.
Oceans, climate, time
Currents, carbon, climate vs weather, relative and absolute age.
Minerals and water
Minerals and Mohs, water cycle, groundwater, soil.
Hazards and resources
Volcanoes, slides, storms; fuels and ores.
Geologic time and carbon
Relative and absolute ages, the carbon cycle.
Weathering, soil, and the water cycle
Weathering, erosion, soil profiles, and the water cycle.
Earth’s magnetic field
The dynamo, the dipole, inclination and declination, paleomagnetism and seafloor stripes.
Glaciers and sea level
Glacier budget, isostasy, sea level, and glacial deposits.
Groundwater
Porosity, permeability, water table, Darcy, aquifers and aquitards.
Seismic waves
P, S, and surface waves, travel-time curves, magnitude, and Earth’s interior sketch.