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Dupdup Trench

by Chris Wayan, 2005-6

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Map of equatorial Dupdup Trench on Tharn, a mostly dry Marslike world-model.


Dupdup is a trench below the southeast rim of Dejah Upland. It's about 3200 km (2000 mi) long, 1-200 wide, and 3-4 km deep--modest, as Tharnian trenches go. It crosses the equator, where hot, rising air tends to precipitate rain, so two large lakes fill much of the trench floor: Lakes Yegweh and Kyekyek.

Dupdup Trench is flyote land; at least they're the only flying people who've settled this air oasis. Lebbirds and wingbok could certainly fly here too, but they haven't yet reached Dupdup Trench. They may be a long time coming--it's 2000 km over jagged mountains to the next oasis where people can fly. Bos, lobbras and thotters live here too, but being wingless, they enjoy only the dense air's secondary benefits: a stable hot climate, reduced UV (lush crops, no sunburn), invigorating air and fertile land. But it's the flamboyant (indeed, buoyant, in this dense air) flyotes who run the show--they dominate both numerically and culturally. It's only natural; flyers get (and spread) all the news first.

To the north, the trench leads to the Artolian Chaos and Ohh Forest on the Sea of P'tang, a land dominated by huge elaffes. To the northeast is Lushanta Veldt, a rolling savanna 1000 km wide; due east, Ksaksa Sea and Polodona Forest, where bos are a majority; to the south and west, huge Felatheen Veldt, home to three grazing species, and to the northwest, the Aihu Range, a spur of Dejah Upland, where mops and camaroos predominate.


The hot, rainy shores of Lake Yegweh straddle the equator. They'd be the hottest place on Tharn, if the skies weren't so cloudy. Cloudy for Tharn, I mean--most days in orbital winter, the sky's a deep blue dappled with puffy clouds, alternating sun and mild showers; in orbital summer, torrential rains fall, though it's not relentless--between storms you get windows of sun. It's never cold and often hot. The heat and rain make the shores of Yegweh as lush as the Amazon, despite the Alpine air pressure--after all, that's twice normal for Tharn, and both flora and fauna luxuriate in it.

The only winged people taking advantage of that air are flyotes. But these aren't the desert-canyon dwellers you've met elsewhere on Tharn--simple farmers living in cliff-houses above irrigated fields. Dupdup flyotes don't even resemble other trench-dwelling flyotes. Three factors have shaped their bodies and culture: dense air, of course (increased stature and brain size), isolation (this is the only flyote-dominated trench; elsewhere they're minorities in civilizations dominated by lebbirds, arthom and others) and the jungle itself.

A wolf-sized flyote, a winged, intelligent canine, of Dupdup Trench on Tharn, a biosphere much like a warm Mars. Based on a drawing by ShinigamiGirl of VCL.
The sketch of a Dupdup woman above is typical; quite wolflike in size (though not weight; hollow bones). We're on a ledge high above the trench proper; in the rainy season, Dupdup flyotes will often ride updrafts above the cloud layers to get some sun.

The landscape is a bit deceptive: we're near the shallow, drier northeast end of Dupdup Trench. Atop these bluffs in the background is savanna, and the trench floor is a pleasant open wood, not a jungle. But most of Dupdup is greener; in the far south, it gets quite wet--and lush. We'd call it true rainforest.

Deep in Dupdup's heartland, flyotes live in treetop villages, practice silviculture (tending fruit and nut trees for most of their food), siesta in afternoon and dine by Zeus-light in the cool of the night--no need for fires in that brilliant, warm light, like a thousand full moons. They'd seem lazy to desert flyotes--no ditch-digging, no cave-chipping. Languid and sensual, in the humid heat. Polynesian? Readers who've visited other Tharnian trenches will feel deja vu: these flyotes behave remarkably like lebbirds in other jungle trenches--arboreality, nocturnality, the whole pattern right down to body language. It raises the question: is lebbird character itself just a cluster of adaptations ideal for a big rainforest flier? A thotter, a large, intelligent otter, leans on a fish-spear and looks out over a mountain lake in the Wabba Basin on Tharn, a biosphere-model much like a warm Mars.


North of Lake Yegweh lies an odd area called the Wabba Spur, a young (or abortive) arc basin. Here the Aihu Mountains draw back, and several parallel valleys break off from the main trench, widening the lowland jungle into a triangle 500 km on a side, from Yegweh's shores to the Wabba Lakes. This twisting chain of lakes--the largest, Wabba itself, is a C-shape 200 km long (125 mi)--range in altitude from bedlevel to two km down. Since the spur is shallower, air pressure is lower; more bos and thotters call Wabba home than flyotes. Above the lakes soar the jagged, broken peaks of a very different range: the Artolian Chaos, a maze of blind valleys and lake basins like nothing on Earth, and with an unearthly cause: converging shockwaves from the Heloon impact. Crags and falls (based on The Sentinel in Yosemite in the floods of 2005) in the Aihu Range on Tharn, a biosphere-model much like a warm Mars. Click to enlarge.

In between, poised on the brink between high Artol and deep Wabba, is Yakkakee Ring, 175 km wide (110 mi), looking from space like a lake-filled impact crater or huge caldera. But the rocks say otherwise: Yakkakee is a gigantic sinkhole, a round plug of sagging crust over a downwelling plume of magma--the reverse of a volcano! Odd features like this, called 'coronae', are quite common on Venus, but rare on cooler worlds like Earth and Tharn. Yet several more possible coronae are visible in the orbital photos, around the edges of Wabba Spur.

In short: the Wabba Spur is tilting, fracturing, churning up and swallowing the eastern edge of this older upland in unearthly but vigorous ways. The main practical consequence is that quakes are common in Wabba and northern Dupdup. So the local flyotes' preference for treehouses over traditional cliffdwellings may not be some mysterious lebbird-mimicry, just tectonic commonsense!


South of Yegweh the trench is a bit drier (it couldn't get wetter). So the next lake on the trench floor isn't nearly as deep, and its shores are fully 4 km down, the lowest in Dupdup. With no outlet but evaporation, Lake Kyekyek is brackish; both Lake Yegweh to the east and Yipyaa to the west drain into it. The salt has cultural consequences: people congregate along the many streams descending from the Aihu Mountains. Multispecies towns cluster around stream-mouths, dominated by thotters--elsewhere they live out on islands and capes, but here they live alongside veltaurs, flyotes and bos. It's a fascinating hybrid culture--certainly the only place on Tharn where you'll see a scaly bo dressed to the teeth trance-dancing thotter style, shouting life-questions to the dance gods...

LAKE YIPYAA and the NEIRA RIVER Carved wood effigies of guardian figures seen in the dreams of 'mops', a velociraptor-like people on Tharn, a biosphere-model much like a warm Mars.

West of Dupdup Trench rise the Aihu Mountains, in a spectacular, Himalayan front--icy peaks standing 9-10 km (30-33,000') above the steamy tropical trench. The abrupt rise snags storms--the slopes of Aihu are tall hardwood forests with torrential rains, especially in orbital summer.

The woodcarvers of the region are famous. They're a wingless but heavily feathered cold-tolerant species called mops. Above, in alpine meadows, a second mountain people, camaroos, herd flocks up to the snowline. The proximity of such diverse habitats has led to cultural borrowing; the bos and flyotes of the trench carve wooden house-posts and panels much as mops do; even their depictions of winged guardian spirits look quite moppian.

Over the great range is Aihu Valley, a broad arc basin 1600 km (1000 mi) long and hundreds wide. At its upper end lies Lake Neira, two km high, cupped in "oak"-studded Mediterranean hills. From it, the Neira River runs down the length of the basin, down through savanna with scattered groves, then dry treeless veldt. The Neira runs around the end of the Aihu Range, then turns sharply down into Dupdup Trench, collecting tributaries from a thousand miles of Felatheen Veldt as it descends. From Lake Yipyaa the Neira flows on down to Lake Kyekyek, the trench's lowest point. It ends up not far from its source... just ten kilometers lower!

"Aihu" and "Neira" are both veltaur names; the hills and plains around Lake Neira are about the highest, coolest habitat on Tharn for these playful, social grazers. Veltaurs evolved on hot savanna, so they're normally rangy, big-eared and thin-pelted. If tropical humans settled Neira, they'd simply wear coats; but veltaurs are just too fidgety and nervous to tolerate clothes. So their adaptation was slow, difficult, and biological: the Upper Neira subspecies is uniquely shaggy (and zebra-striped). They're an especially startling contrast to their slender heat-adapted cousins in the sweltering depths of Dupdup. Orbital photo of Dupdup Trench and Ksaksa Sea on Tharn, a mostly dry Marslike world-model.


The hills and plains east of the trench around Ksaksa Sea are warm and wooded--neither as hot or as torrential as the trench, but warm and rainy. This is just the western edge of Polodona Wood, the greatest rainforest in this hemisphere, covering perhaps 2M sq km (as big as Indonesia or the Orinoco Basin).

In its heart, annual rainfall's about 1.8 m (70")--not a true rainforest by Terran standards. Tharn's year is short, so in one Earth year the woods get more like 90", but this is offset by faster evaporation in the thin air. But in the end it's not numbers that make me call Polodona a rainforest. Tharn's vegetation is used to high evaporation and long dry seasons; year-round moisure in any amount is a bonanza. Polodona is lush. Two 'bos', people resembling kangaroos, in a rainforest on Tharn, a biosphere-model much like a warm Mars.

Only one Tharnian people is well-adapted to rainforest: the semi-arboreal bos; they overwhelmingly predominate here. A thotter, a large otterlike person, on Tharn, a biosphere-model resembling a warmer Mars.

You will find thotter villages along rivers and the Ksaksa seacoast. They escape the muggy heat by taking midday water-siestas.

You'd wrinkle. They don't.

Map of Tharn, a world-building experiment. Click a feature to go there.
Gazetteer: index of place names with descriptions. Or TOUR THARN! The following route snakes around Tharn, covering all major features
Tarkas Upland -- Tars Triangle -- Thoris Upland -- Raksar Sea -- Llana Upland -- Barsoom Basin -- Jahar Range -- Heloon Crater -- Heloon Desert -- South Pole -- Sola Upland -- Otz Trench -- Thuvia Upland -- Mrr Trench -- Far North -- Rronk Woods -- Parthak Crater -- Hastor Sea -- Varo Sea -- Yoof Trench -- Dejah Upland -- Dupdup Trench -- Felatheen Veldt -- Chinchak Mts -- South Seas -- Polodona Wood -- Sea of P'Tang

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