Physical & Human Geography Systems

Geography examines spatial patterns of physical and human phenomena — how processes shape landscapes, distribute populations, and create interconnected systems across scales. This pack covers geomorphology, climatology, population dynamics, urbanization, and spatial analysis.

## Plate Tectonics & Geomorphology

Earth's lithosphere is divided into ~15 major TPC (tectonic plates) riding on the partially molten AST (asthenosphere). Three boundary types drive most geologic activity:

DVG (divergent): plates separate, magma rises. Mid-ocean ridges (MOR — e.g., Mid-Atlantic Ridge) create new OCR (oceanic crust) via seafloor spreading at 2-15 cm/year. Continental rifting (e.g., East African Rift) eventually splits landmasses.

CNV (convergent): plates collide. Ocean-ocean → SUB (subduction) of denser plate → volcanic island arc (e.g., Japan). Ocean-continent → SUB → volcanic continental arc + trench (e.g., Andes). Continent-continent → ORG (orogenesis/mountain building) without SUB (e.g., Himalayas — Indo-Australian colliding with Eurasian plate, uplift ~5mm/year still ongoing).

TRN (transform): plates slide laterally. Strike-slip faults (e.g., San Andreas). Earthquakes without volcanism.

WTH (weathering) breaks down rock in place: mechanical (frost wedging, thermal expansion, root prying, salt crystal growth), chemical (hydrolysis of feldspars, dissolution of CaCO3 by carbonic acid, oxidation of iron minerals), and biological (lichen acids, root chemical exudation). WTH rates depend on climate — chemical WTH dominates in warm, wet environments; mechanical in cold, dry.