Earth's interior: Crust (outer layer, 5-70 km thick — oceanic crust thinner/denser than continental), Mantle (middle layer, extends to 2,900 km — convection currents here cause tectonic movement), Core (innermost — outer core is liquid iron/nickel, inner core is solid). Lithosphere = Crust + upper mantle. Asthenosphere = partially molten upper mantle where tectonic plates float.

Latitude and Longitude: Latitude = angular distance north/south of equator (0° to 90°N/S). Important latitudes: Equator (0°), Tropic of Cancer (23.5°N — passes through Rajasthan's Banswara/Dungarpur), Tropic of Capricorn (23.5°S), Arctic Circle (66.5°N), Antarctic Circle (66.5°S). Longitude = angular distance east/west of Prime Meridian (Greenwich, 0° to 180°E/W). IST = GMT + 5:30 (82.5°E longitude, passes through Mirzapur, UP).

Types of rocks: Igneous (formed from cooling magma — granite, basalt), Sedimentary (formed from deposition and compaction — sandstone, limestone, shale), Metamorphic (formed from heat/pressure transformation — marble from limestone, slate from shale, quartzite from sandstone). Rock cycle: Igneous ↔ Sedimentary ↔ Metamorphic (any rock can transform into any other type).

Atmosphere layers (ascending): Troposphere (0-12 km — weather occurs here, temperature decreases with height), Stratosphere (12-50 km — ozone layer here, temperature increases), Mesosphere (50-80 km — coldest layer, meteors burn here), Thermosphere (80-700 km — ISS orbits here, ionosphere within this layer enables radio communication), Exosphere (700+ km — merges with space).

REET Exam Tips: 5 questions — focus on Earth's layers (crust-mantle-core), important latitudes (Tropic of Cancer through Rajasthan), rock types and transformations, and atmosphere layers in order with key feature of each.