• AMAZONIAN: rainforests as tall, dense, wet and warm as the Amazon--but such forests are only the second densest biomass on Venus--the deepest rainforests, utterly dwarfing Earth's, are dubbed MEGAZOIC.
• ARACHNOID: see TICK.
• ARCUATE: crescent-shaped. Venus is a curvy place. The edges of coronas often have ridges, valleys, lakes, and (if the sea level's right) islands, all shaped like fingernail-parings. Sometimes a ring of arcuate islands around a "blue hole" is all that's visible on the surface. Partly buried impact craters also create arcuate shapes. And calderas can have arcuate cliffs, some of them miles high--the most impressive arcuate features of all.
• BLUE HOLE: Venus's seas are generally shallow, but scattered through the turquoise coral shallows are round indigo pits, tens to hundreds of kilometers wide. The heat of Old Venus made crater walls sag over time, so old craters are mere round wells; they rarely form ring-islands as they often do on Mars. Also, some coronas sag instead of bulging; if they're undersea, they can be indistinguishable from old impact craters. And undersea chasmas create narrow blue rifts. Blue holes can cup stagnant pools of cold salty water, or they may divert currents and generate whorls or plumes rich in nutrients, downstream.
• CALDERA: a large volcanic crater, often lake-filled after terraforming. Many had overlapping vents, so various cliff-walled pits of different depths combine into complex shapes.
• CENOTE: a pit-lake, a cliff-lined "well" with a lake filling the bottom. Properly a feature of limestone country, which Venus lacks--but analogous lava structures do exist, often in chains, and on quite a large scale, though they're usually called fossae--"cracks", a catchall term.
• CHASM, CHASMA: a deep valley, usually a winding groove walled by twin ridges, often quite high and steep. The best Earth analogy are rift valleys as in East Africa. With terraforming, they often hold long narrow lakes, like Baikal or Tanganyika on Earth. Chasma is often anglicized as Chasm, Rift, or Valley, and sometimes, if underwater, as Trench or Deep--but when the ridges predominate, a chasma may show up as a mountain range, ridge, island or chain.
• CORONA: a round or oval blister, sometimes bulging, sometimes sagging, sometimes popped--occasionally a smooth dome but usually with concentric ridges and rifts. Coronas are big--from 100 to 1000 or more km across. If you count Artemis, make that 2500 km across! They're probably upwellings from the mantle, but just possibly down-wellings that pull surface stuff together. After terraforming, "corona" often becomes terms like
  • dome (a relatively smooth highland)
  • hills
  • arc (a broken or partly flooded corona)
  • eye (a sagging corona cupping a central lake)
  • blue hole (see).
• CRATER: always an impact crater, not volcanic (see CALDERA). Because Venus's air was so thick before terraforming, smaller meteors burned before they hit the ground, so no small craters formed. But erosion was slow, so the few really big scars survived much longer than on Earth. The result: nearly 1000 large craters, but none under two kilometers across. Most have low walls, compared to Mars; the heat of old Venus made them sag over time. Many are just circular pits.
• CYTHERAN (variants: Cytherean or Cytherian): Venusian. No one uses that term, though--in English it sounds like, ummm... latex aliens in bad 1950s movies. And Venerian sounds like a disease unless you're Russian. So Cytherean, from the minor Greek goddess Cythere, is the most common adjective, though no single spelling dominates the literature.
• DEEP: a deeply flooded chasma or rift; usually a narrow sound flanked by the twin ridges typical of a chasma. By Terran standards, deeps aren't that deep--just a mile or two.
• DORSA, DORSAE: ridge, straight mountain range.
• FARRUM, FARRA: see PANCAKES
• FLUCTUS: flow, lava flow. Venus was so hot that lava could flow up to 6000 km before solidifying (not a typo! Six thousand.) Most of the big flows are now undersea; some are capes just above water. Small flows through uplands often became riverbeds--drainage is drainage, after all.
• FOSSA, FOSSAE: cracks. Usually, straight narrow canyons caused by crustal stretching. Today, fossae often hold rivers or fingerlakes. A second sort of feature once called fossae, oval or chained subsidence pits, aren't stretching-scars at all: lava drains out from under the crust, which collapses. After terraforming, these often become pit-lakes called cenotes.
• HADLEY CELL: a loop of air, rising in a warm region, then traveling north or south as a high-altitude wind until it cools and grows denser, dropping back to the surface as a cool dry wind that heads back to where it rose, warming and picking up moisture as it goes. The rising zone is usually rainy; the falling zone, arid. Venus has two Hadley cells per hemisphere, where Earth has three.
• MEGAZOIC: rainforests unique to Venus--hotter, taller and denser than any on Earth--in some places, taller than redwood forests, and much faster-growing. Around the edges of Megazoic zones are lesser rainforests dubbed Amazonian.
• MONS: mountain of any sort.
• PANCAKES: flat round lava mesas, 1-10 km across, with 100-meter cliffs at the edges. The name's not just whimsical: they formed much like pancakes, from frothy lava-upwellings that solidified first at the edge.
• PATERA: a volcano with a wide caldera (crater). On Venus, most are low, broad shield volcanoes like Hawaii.
• PLANITIA: a low plain. After terraforming, this may as well be translated "sea": nearly all planitia are under water.
• PLANUM: plain or plateau. After terraforming, those more specific terms usually replaced planum, though Lakshmi Planum is still used as much as Lakshmi Plateau.
• RAINSHADOW: a mountain range or desert can strip winds of most of their moisture, so no rain falls downwind--they cast a rainshadow! Single mountains can cast small rainshadows on their own downwind slopes. Or rainshadows can be continental in scale--even an island may be in a rainshadow if its usual wind blows off a dry continent nearby. On the other hand, seas and rainforests moisten winds passing over them, erasing rainshadows. And mountains or ridges casting rainshadows often trap enough rain to nourish high-altitude forests on their slopes, and send streams down into dry country at their feet, creating vital oases.
• REGIO: region, land. Little used after terraforming.
• RIFT: properly, a chasma where tectonic plates are spreading or slipping; but used rather loosely on Venus, where plate tectonics are in an embryonic stage (or were); here, it's just a shorter word for Chasma, especially the central valley as opposed to the ridges.
• RUPES: cliffs, scarps or steep slopes.
• RINGWALL: the circular rim of an impact crater.
• RINGS, RINGSHADOW: a complex of variously tilted artificial rings now orbit Venus, shading the equator and to a lesser extent the mid-latitudes. The result is a relatively mild dry equatorial zone flanked by jungly torrid zones around 45 degrees north and south. Convection patterns confine most of Venus's deserts to the equatorial zone.
• SCARP: a sudden, steep slope or break. A broader term than cliff, which implies a near-vertical drop. Still, some scarps are true cliffs.
• SCORPION: See Aphrodite.
• SPIDER: see TICK
• SPLASH APRON, SPLASH RIDGES: When a meteor blasts out a crater, not all the material ends up in the ringwall. Both molten and solid debris falls outside the crater rim, usually thickest near the wall and tapering off--an apron. Splash ridges are radial lines of rugged debris, like rays around a child's drawing of the sun. They glow white on radar scans, in stark contrast to smooth black crater floors.
• SULCI: Wrinkles, folds, roughly parallel ridges, like many hill-ranges on Earth.
• TERRA: literally just "land," virtually interchangeable with "regio." But on terraformed Venus it's come to mean a giant island--over a million square kilometers. Earth has only one such not-quite-continent, and it's iced over: Greenland. Venus has over a dozen.
• TESSERA, TESSERAE: tesseration (literally "tiling") means fields of wrinkles that intersect to make grids or nets of repeating landforms. May resemble a brick walk (mesas in a grid of valleys), or a waffle (pits in a grid of ridges; the pits often fill up, leaving a grid of small lakes.) Unlike waffles, tesserae may not be right-angled; and the intersecting wrinkles may run in MORE than two directions. You can get many strange textures--brain coral, nail files, alligator skin... Terra's tessera are few and small: cracked mudflats, or Arctic tundra studded with hexagonal ponds and pingoes (turf-clad ice pyramids).
• THOLUS: a steep volcano, like Fuji--conical or a dome. Contrasts with PATERA, a low, broad vent with a wide caldera (crater).
• TICK: a pancake with radial ridges, looking like a tick or spider from above. Ticks are unstable--the legs are eroded edges. Terraforming's winds and rains can cause further slides.
• UNDAE: the Latin plural of underwear. No, no, I lied. Undulations--winding, snaky ridges, like the earthworks that the Mound Builders left in America. Wiggly sulci (see).
• VALLIS, VALLES: valley, valleys. Given Venus's primitive drainage, they're often lakes.

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