Acasta gneiss: the old world -- Allochthon: rocks that roam -- Amethyst: purple haze -- Amygdule: on the bubble -- Anthropocene: it's about time -- Areology: wars of the worlds -- Benioff-Wadati zone: off the deep end -- Bioturbation: the worm churns -- Boudin: secrets of sausage making -- Breccia: you're breaking up -- Brimstone: volcanic theology -- Chondrite: recipe for a small planet -- Cryogenian: many are cold but few are frozen -- Darcy: a truth universally acknowledged -- Deborah number: beyond measure -- Dreikanter: three, of a kind -- Eclogite: pulling its weight -- Ediacara: peaceable kingdom -- Erg: the sands of time -- Firn: snows of yesteryear -- Gastrolith: from the gizzards of lizards -- Geodynamo: electromagnetic blanket -- Geophagy: raw terroir -- Geosyncline: magic mountains -- Granitization: igneous agnostics -- Grus: things fall apart -- Haboob: dust in the wind -- Hoodoo: hats off -- Jökulhlaup: breaking the ice -- Karst: the holey land -- Katabatic winds: blow me down -- Kimberlite: diamonds are ephemeral -- Klippe: strata gone astray -- Komatiite: the rock that went extinct -- Lahar: abhorrent torrent -- Lazarus taxa: zombie fossils -- Lusi: its name is Mud -- Moho: setting boundaries -- Mylonite: faulty logic -- Namakier: salt - water = taffy -- Nuée ardente: cloud with a white-hot lining -- Nunatak: peaks in a blanket -- Nutation: nodding off -- Oklo: the original Manhattan project -- Ophiolite: crocodile rock -- Panthalassa: oceans of time -- Pedogenesis: dirt rich -- Pingo: young as the hills -- Pneumonoultramicroscopicsilicovolcaniconiosis -- Polynya: window of opportunity -- Porphyry: all crystals great and small -- Pseudotachylyte: hot flashes -- Rapakivi: oddballs -- Scree: slippery slopes -- Skarn: a slow roast -- Slickensides: science fiction -- Speleothem: drip feed -- Stygobite: what lives beneath -- Stylolite: marble marvels -- Sverdrup: current affairs -- Taphonomy: what becomes a fossil most -- Thalweg: the valley below -- Thixotrophy: call me quick -- Tiktaalik: fish out of water -- Tully Monster: alien autopsy -- Turbidite: muddy waters -- Twist hackle: give me a break -- Unconformity: conspicuous absence -- Uniformitarianism: same as it ever was -- Varve: dear diary -- Xenolith: wayfaring stranger -- Yardang: gone with the wind -- Yazoo: parallel lives -- Zircon: I will survive -- Appendix 1. Simplified geologic timescale -- Appendix 2. Entries by language of origin -- Appendix 3. Entries by topical category -- Appendix 4. Entries by geographic location -- Appendix 5. Biographical references.