Earth science
Oceans, climate, time
Currents, carbon, climate vs weather, relative and absolute age.
Basics
Oceans
Surface currents: wind and Coriolis (Ekman, gyres). Deep water: temperature and salinity density (thermohaline). El Niño is a shift in equatorial Pacific temperature and pressure.
Climate
Weather is day-to-day; climate is the long-term statistics. Greenhouse gases (CO₂, CH₄, H₂O, …) absorb infrared and keep the surface warmer. Milankovitch cycles are orbital changes on ice-age scales.
Geologic time
Relative: superposition, cross-cutting, unconformities, fossil assemblages. Absolute: radioisotopes (e.g. ¹⁴C, ²³⁸U). Precambrian is most of Earth history.
Formulas
Half-life
Age from remaining parent isotope. ¹⁴C for thousands of years; U–Pb for hundreds of millions.
Symbols
-
t_{1/2}half-life -
Nremaining nuclei
Residence time
Reservoir size divided by the flow that fills or empties it. Used in water and carbon cycles.
Symbols
-
τresidence time
Key table
| Seawater | mean salinity ~35 PSU (‰) |
|---|---|
| Phanerozoic | from ~540 Ma — conspicuous fossils |
In this field
Rocks and plate tectonics
Rock cycle, earthquakes, volcanoes, plate boundaries.
Atmosphere and weather
Layers, wind, clouds, fronts.
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.