How weather works

earth-sun geometry and its effects on the global weather system

Hadley cells

Inter-tropical Convergence Zone (ITCZ)

model of global winds and semi permanent high and low pressure

monsoons

ocean gyres

major ocean currents, their direction of flow and relative temperature

El Nino/La Nina

Climate classification - specifically the Köppen System know what the major categories are and roughly where they are located.

Tectonics and Geomorphology

theory of plate tectonics and continental drift

general theory of earthquakes, volcanoes, faulting and orographic processes

where major zones of subduction cause earthquakes and volcanoes

Soils

major classification systems USDA versus the UN's FAO 

some sense of how soils differ and where major soil groups are located

Biome classification - major plant/animal associations and rough locations

altitudinal and latitudinal zonation

Environmental Threats and Hazards, attempts at mitigation

General tools of Remote Sensing and Geographic Information Systems