“You like the names.”
“Yes,” surprised, “I do.”
He led Wade under the side of the glacier, right up to its faceted cliff of a sidewall, which gleamed pale blue in the bright sun. Spills of broken ice splayed out from the wall here and there, as if ice machines had churned out a vast oversupply of ice cubes. “See how rounded all the chunks are,” Michelson pointed out. “They’re subliming away in the arid winds, and they’ll be gone before there’s another calving in the same spot. That’s why there’s no build-up of ice, and the glacier’s sides are sheer like this. They break off as a result of slow pressure from behind, and then the wind cleans up the mess at the bottom.”
Eventually they climbed onto a section of rubble bordering the glacier that ramped up until it was level with the broad surface of the glacier, then just above it, so that they could see beyond the glacier, and a long way up the ice plain of the polar cap, rising gently to the south. It was not perfectly smooth, but had broad undulations that formed very low hills and valleys, Wade saw; subtle contours of up and down, all very smooth except in certain zones, where it was completely shattered. A kind of white frozen ocean, pouring through a break in the shore and down to a lower world. Also curving down in places to stand right over the shore, like waves that would never break. Puffing, sweat stinging one eye, Wade was nevertheless fascinated by the sight, glaring even through his polarized sunglasses; it was surreal, a kind of Dalí landscape, with all its features made impossible and subtly ominous, as the ocean bulked higher than the land, and one surge of the immense white wave would sweep them all away.
But of course it stayed put. Michelson had hiked ahead, and joined Graham Forbes between the glacier and a broken cliff of reddish stone facing it. There at the foot of the red stone was a band of lighter sandstone, freckled with pebbles embedded in it. Graham Forbes was already kneeling before this sandstone, tapping away with a geologist’s hammer.
“Now this is a very nice example of the Sirius group,” Michelson said as Wade approached them. “Almost a textbook example of it, in that it would make a good photo in a textbook. See how it’s laminated against the dolerite? Like the dirty ring of a bathtub. It’s a sedimentary rock, called tillite or diamictite, depending. Glacial till, from an ancient glacier.”
“Not from this one?” Wade said, gesturing at the ice mass looming behind them.
“No, from a predecessor. It’s been here a while.”
“How long?”
A snort from Forbes.
Michelson’s moustache lifted at the corners. “That’s the question, isn’t it. We maintain that some Sirius group sandstones date from around three million years ago.”
“Other people don’t agree?”
“That’s right. There are those who say that the eastern ice cap has been very stable, and has been here for fourteen million years at least. So—” He shrugged. “We look at Sirius sandstone wherever we can find it, and see what we can see.”
“How have you established the three-million-year date?”
“There are microfossils buried in the rock, the fossil remnants of marine diatoms and foraminifera. These creatures have evolved over time, so that different kinds have lived in different eras, and the diatom record on the ocean floor is very well stratified and preserved. So when you find certain kinds of diatom fossils, you can match them with the record and say with fair confidence that the rock they are in is of a certain age.”
“And this is a real method—I mean, an accepted method?”
The little smile. “Oh yes, very real. It’s called biostratification, and it’s very well established.”
“I see.”
“We’ve also found evidence of a fuller biological community than just marine diatoms—members of a beech tree forest biome. Which suggests it was so warm that the ice cap would have been substantially gone, with western Antarctica an archipelago, and even eastern Antarctica covered in parts by shallow seas.”
“You carbon-14 dated the beech trees?”
“No no, carbon-14 dating only works for a short distance back in time. These are much older. And beech trees have remained stable evolutionarily for many millions of years, so we can’t date them by their type. There are some beetle fragments among the beech remains, however, and some other plants, lichens and mosses, and some of these can be dated using various methods, uranium-lead, argon-argon, amino acid … every little bit of biological material in Sirius tends to add its part to the puzzle.”
“Look,” Forbes said to Michelson, pointing with the geologist’s hammer to the rock of the slope at about his knee level. “A dropstone of diamictite, within the massive diamicton here.”
Wade saw that a round boulder of sandstone, the same color as the rest but with more pebbles in it, was embedded in the rest of the sandstone.
“Interesting!” Michelson said, going to one knee to have a closer look. “So this boulder must be very much older than the matrix.”
“Older, anyway,” Forbes allowed.
They continued to discuss the band of sandstone, pointing out features invisible to Wade. “Do you think this could be our D-7 disconformity again, cropping up here?”
“It looks like that could be some crude stratification below it, see that.”
“And above, massive clast-rich diamictite, with dolerite boulders, and more water-lain gravels.”
Back and forth they went, in a flurry of terms, as they wandered up and down the slope: deformed laminites, clast-poor muddy diamictite, rudimentary paleosols, lonestones, metasediments; “And then at the bottom the Dominion erosion surface again, perhaps. See how scoured this dolerite is, with north-south striations.”
“Very nice,” Michelson said.
They were seeing much more in this rock than Wade had ever realized could be there, much as he might hear more than them if confronted with an unfamiliar piece by Poulenc. They were reading the landscape like a text, even like a work of art in some senses.
“See here!” Michelson exclaimed to Forbes, pointing at a patch of whitish rock at one end of the sandstone band, laminated very finely. “Silt layers, calcite crystals perhaps, and deposited here certainly—these couldn’t have been moved here, they’re much too delicate, see? You can break the layers with a finger.” He demonstrated. “Beautiful.”
“I’ll take some samples,” Forbes said, getting a flat rectangular white canvas bag out of his daypack.
“Is this the first time you’ve found this kind of thing?” Wade asked, feeling pleased: a scientific discovery!
“The first time here, anyway.”
“And what does this indicate?”
“Well, these silt or clay layers suggest the bottom of a lake, and as you can see, boulders have dropped onto the layers while they were still wet and could be bowed down under the weight, see that? One explanation of that could be that this was a lake in a glacier’s margin, and icebergs calving would melt, and drop the boulders in them onto the silt on the bottom of the lake. We certainly see results just like these around living glaciers. So we may be looking at the bottom or shore of a lake.”