by Chris Wayan, 2006
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Agassiz Basin
The Agassiz Ocean was once the southwestern Pacific. It's one of the largest remaining seas--a fairly compact, unbroken triangle of water as big as our Arctic Sea, over 12 M sq km (5 million sq mi). That comparison's a poor one: the Agassiz is not just warm, parts of it are hotter than any sea on Earth today. Though much of it lies in the high latitudes, the climate's still mild at 50-60 south and sauna-like near the equator. The reason? Sea level is very far down indeed, fully 5 km (3 mi) below ours. In this deep well, air pressure is 1.7 times normal, trapping heat, flattening temperature swings, and filtering ultraviolet.
Let's circle the Agassiz Basin and have a look at its regions. I'm still constructing maps of this region, since the sea floor here is one of Earth's least-known and most poorly documented regions. To the right is a rough altitude map. Green areas have air denser than one atmosphere; yellow, roughly like our sea level; orange and above, thinner, mostly like Earth from one to two miles up. Remember, the colors do NOT indicate rainfall or vegetation! And the real coastline is far more complex; this is largely from late 20th Century soundings (i.e. not terribly accurate even before I oversimplified them).
The east coast, south of the Polynesian Ranges, is dry and hot, the second hottest in the world (after the Baja Desert). Prevailing winds here blow off the land; storms from the seas to the east rarely manage to cross the Ducie Mountains, culminating in Mt Pitcairn, 5330 m high (17,500'). The Agassiz Lakes, in a rugged fracture zone, are deep enough not to be seasonal, but only a few rivers here reach from the mountains to the sea. A series of jagged "fjords" cut this coast; low, barren ridges divide lush fingers of coral reef, something like the fingers of the Red Sea around Sinai, but dozens. Volcanic islands like Marie Therese and Legouve offshore are tall enough to snag clouds on their wooded shoulders.
Further northeast, the coasts below the three great Polynesian Ranges would be scorching desert if the air pressure were like Earth's. These plains (and the valleys between the Polynesian chains) still get no rain during most of the year; but in high summer, the desert air to the southeast heats and rises, sucking great storms from the Penrhyn Gulf (northernmost Agassiz); the mountains block much of the rain, but enough gets through to sustain open monsoon woods patchy with meadows (like the central Outback), and replenish seasonal lakes and marshes. Though not all are seasonal: Lakes like Tubuai and Tahiti in the west, and huge Lake Moruroa in the east (600 km/370 mi long) are deep and stable; in the dry season, they're fed by delayed runoff in the form of springs from the Polynesian Mountains around them; last season's rains percolating through porous limestone, once coral reefs.
As we head northwest, past Mt Wachusett, a snowless but forested volcano 5 km high looming over the coast, the rains grow heavier and last longer. Mt Haymet and Mt Fabert are wooded to their feet; after this it's solid forest. No wonder. Past Cape Beveridge and around Manihiki Bay, the northern shores of Agassiz face fierce storms almost year-round. The mean rainfall's 2.5 meters (100"). It's sweltering, too, except for the Manihiki Highlands. Slopes on the western shore of Manihiki hold Siphonia's rainfall record--up to 20 m (nearly 800"), nearly double Earth's wettest spot on Kauai. The Manihiki uplands are a chain of ecological islands--former atolls and lagoons now high up, in a cool, perpetual spring. Misty fern forests, but few running streams; like Polynesia, these coral-capped volcanoes are porous and cave-riddled. Waterfalls burst from their flanks lower down, where limestone ends and lava begins.
The sketch below, based on the newest data I've found, is still rough but gives some idea of the full complexity of the coasts and climates of the Agassiz.
The western shore of the Agassiz is simple: a brutally straight line, rising fron a deep offshore trench swiftly to the Kermadec Mountains, 5 km high. This mountain wall traps storms nearly as heavy as in Manihiki; the Kermadecs are clad in belts of steamy rainforest hotter than anything on Earth, through Amazonian rainforest, upland cloud forest, fern forest, and finally alps. Peaks are snowy in winter but not glaciated. The back side of the Kermadecs, in Lau Valley, is open dry grassland, with trees only along the Lau River and a few lakes.
The rugged, spectacular Louisville Islands have varied climates. If you don't like the weather, just climb, for these huge whalebacks rise 3-5 km from sea level, from hotter-than-tropical into cool-temperate zones; the southernmost even have glaciers on the shady sides of their summit ridges.
The cooler highlands of Chatham and Campbell and the Bounty Valley, more like Earth's cool-temperate zone; winter is harsh, especially in Chatham. Since the air's in these uplands is as thin as on our Earth, they're the one area that lacks the distinctive flying species of the Agassiz Deep (see LIFE IN THE AGASSSIZ below).
Eltanin, the warm-temperate south shore of the Agassiz, is almost European; if not for the creatures flapping around in that dense air, it could almost be France.
Menardia, in the far southeast, has a gentle Californian climate. Even the topography's milder; instead of the savage volcanic verticality of the north or the pseudo-fjords common along other stretches of rift zone, only a few great fossae (linear canyons) break Menardia's broad, grassy, oak-dotted plains. The few fossae are classic: cliffwalled and lake-bottomed, running thousands of km. But if you ignore their geological origins and squint your eyes, you could convince yourself you're on America's west coast, or parts of Australia. Until one of the local people flaps by...
Which leads us to our next topic:
LIFE IN THE AGASSIZ
The Agassiz is one of only two seas fully 5 km below the old sea level. Beside trapping heat, the high air pressure makes flight easy. Even quite large mammals glide on skin flaps from tree to tree, and many fly.
Including the people. No, not humans. In the north at least, it's too hot for them: up to 50 C (120 F) and 100% humidity! The dominant species here will be giant parrots. Even our parrots are as bright as chimps, though it took until this decade for the evidence to finally overcome mammalian scientific prejudices. And they manage it with brains weighing only ounces. Bird brains (despite human insults) beat mammal brains for efficiency--by a wide margin!
But the dense air of the Agassiz basin supports fliers as heavy as 25 kg (55 lbs). Most parrots are only a bit over half this, but that's quite large enough for them to have brainweights approaching a pound. They're just as intelligent as a human--perhaps more so. These megaparrots are imposing creatures in other ways as well: brilliantly colored, with much deeper (but still operatic) voices, and wingspans up to 4 meters (13').
Equally imposing are their distant cousins: megaravens. They're even less recognizable, for in these hot basins, black feathers were a sun-absorbing disadvantage; as they grew, they lightened in color, ending up looking more like their close cousins the jays: various mixtures of gray, blue and white. But they're unmistakable: huge heads, rich but hoarse voices, playfulness tinged with a dark irony... really, they haven't changed a bit. A useful tonic to anyone grown tired of parrots' loud good cheer (punctuated by equally loud prima-donna tantrums).
But fliers aren't the only creatures who have grown larger, with startling consequences for brain size. For an example I'll use the species you're most likely to meet here in the Agassiz: a newly evolved people who cope with the heat and humidity in a different way, by hardly coming out of the water, in the day at least. You see them in every port and river town: those big wet furry things chirping at you and wiggling their whiskers. They're descendants of giant freshwater Amazonian otters, of course.
Their quick evolution was one of those unpredictable consequences of radical environmental change. Recent studies show that the size of animals and the number of species (and probably total biomass, too) correlate well with the oxygen content of the air. Earth's atmosphere has varied greatly over its history--in the last billion years alone, it's varied from 13 to 30% oxygen! While the percentage of oxygen on Siphonia isn't much higher than on our Earth, the dense rainforests in the deepest basins like Agassiz have pushed it higher, to 21 or 22%. However, that's merely the percentage. Down in these deep basins, the available oxygen is 70-80% higher--a bigger change than animal life has seen since brains evolved! All that extra oxygen makes it much easier for an animal to grow larger--OR to grow larger specialized, oxygen-hungry organs. Like brains! They're the costliest organ of all, pound for pound--hogs for both calories and oxygen. In an environment where food isn't too hard to get--and these lush coasts qualify--it turns out that supercharged air has freed many nonflying species to grow much larger and more intelligent. Amazonian otters, already big and bright, apparently crossed a crucial threshhold: social intelligence, the ability to understand, predict, and influence other creatures' behavior, became more important as they got less predictable. A spiral of brain-growth ensued, rather quickly tripling brain-size... just as it had in humans and dolphins.
Other than scaling up, they haven't changed much, physically. The main adaptation is to heat: they're gracile, that is, slenderer, with longer limbs. More surface area per pound means a cooler otter: more evaporative heat dispersal when they're on land.
While human intervention was essential in their appearance here, humans didn't breed or genetically engineer them--just gave them ship-passage from the Atlantic Ocean, and the promise of dockside and fishing jobs! Their descendants naturalized, and are found all over the warmer parts of the Pacific basin, including northern Agassiz. Though these otters are adaptable; some are now found in the southern Louisville Islands, at 50 south. It's much warmer than our Antarctic was, of course--air that dense guarantees it never snows, not at 50, and rarely at 60--but still, they've come a long way from muddy tributaries of the equatorial Amazon.
Of course, mentally they've come further still; from animals to people in a geological blink.
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