The High Sierra

So going uphill or downhill creates different kinds of unknowns. Going up, what you can't see is likely to be easier than what you can; going down, what you can't see could be much steeper than what you're on. Either way, you can't see enough of the terrain to be entirely sure which is the right way to go. It's a little exploration.

So, basins are made by glaciers. They're the empty rock containers of the upper ends of glaciers that are now gone. Their floors were therefore under ice for thousands of years. The ice scraped the floor as it flowed down and away. The ridges walling the basin, often in a horseshoe shape, were plucked at by the freeze-thaw cycle of water and ice; chunks of rock broke off after water seeped into cracks, then froze and expanded. When newly broken-off rocks fell on the ice, or got caught in its texture lower down, they were carried downhill and away. The ice mass resting against the curve of the headwall thus slowly ate back into it. Now that the ice is gone, or confined to little residual strips in the shade, the basin floors left behind are typically bare rock, dotted with boulders

SCREE is sand and gravel that will slide under your feet. TALUS refers to bigger rocks, sized from say softballs to refrigerators, with smaller fragments joining them or not. Talus will mostly hold under your foot, but not always. BOULDERS are, yes, boulders, sized from refrigerators to houses. They will almost never move under you, but occasionally one will.

Sierra Nevada is unusual in its combination of a Mediterranean climate and great height. There aren't that many Mediterranean climates on Earth, found as they are behind west-facing mid-latitude coasts, with their brief cool damp winters and their long hot dry summers. There are five, in fact: the Mediterranean itself, southwest Africa, west Australia, Chile, and California. Tall mountain ranges in these regions occur only in California and Chile, with lower (and thus less glaciated) examples around the western end of the Mediterranean itself, in Spain's Sierra Nevada and Morocco's Atlas Mountains.

For the body, the less dense atmosphere means there is both less oxygen to be taken in, and less partial pressure to push that oxygen into your lungs' cells. The body adjusts with a slightly quickened breathing and heart rate that you can't notice or control. This is the cause of altitude sickness; that quickened breathing blows off more CO, than is normal, and this reduces the acidity of your blood. That change in your blood's pH, becoming more basic, causes the various symptoms of altitude sickness, which can include head-aches, nausea, and lassitude. Bad cases are called "acute mountain sickness" and manifest as edema, meaning trapped water in cells. Both pulmonary edema and cerebral edema are very bad for you, and can be quickly fatal, as in, over a matter of hours. Ordinary altitude sickness is an adjustment problem, and your body will reacidify your blood by natural means, usually within a day or two. Diamox speeds up that process in ways not fully understood. The side effects of Dia-mox, mostly its diuretic effect (lots of peeing) and its central nervous effect (tingling and numbness, especially in fingers and lips) are apparently not directly related to the desired reacidification of your blood One mild altitude effect is a lessened appetite. Some people get ravenous up there, but others don't get as hungry as their exertions should have made them. Pim in the latter group, which can be useful when packing food for a tip. When Tim up there I can only eat about a pound of food a day, minus its water weight.

So the Farallon Plate shoved under the North American Plate and dove into the mantle, where the leading edge melted, five to ten miles down. If that melted rock had risen to the surface while still melted, volcanoes would have resulted, and the emergent lava would have quickly cooled to become various kinds of volcanic rock. The Cascades are a volcanic range like that. It happens quite often. In the Sierras, the Alps, and the Himalayas, the melted rock never made it to the surface. It pushed up against the rock over it, but that roof held, so the melted rock slowly cooled down there. That deep slow cooling of melted crustal rock creates granite; and a big mass of granite is called a batholith. The Sierra Nevada batholith emerged into the light of day only after the vertical miles of Earth over it eroded away. Now it extends from a bit north of Lake Tahoe to Tehachapi Pass in the south. If you could see the whole batholith free and clear in the air, it would be shaped something like a backpacker's air mattress: 450 miles long, 60 miles wide, and, because it still extends about six miles deep into the earth, while standing two to three miles above the land surrounding it, about eight or nine miles thick. None of this was a uniform process. The batholith never looked exactly like an air mattress down there; it was maybe more like a band of cumulus clouds, with individual blobs of melted rock mashed together at their edges. Those individual blobs are called plutons. They're lumped together like party balloons, or the bumpy top of a parasail. That's the range as we see it: the slightly rounded tops of about 20 oval blobs, all pressed together. They're often oval rather than circular, averaging around 10 miles by 20 in size.

So, for many years I loved my Stephenson's Warmlites. But they're bulky, and just recently the newest generation of Therm-a-Rest air mattresses, some of them called the Neo-Air, have become the best yet: warm, light, tall, comfortable, easy to blow up, and compact when packed. You can be about as comfortable as you are at home in bed. Always take one that extends from head to foot, of course.

We knew just enough to realize this was a Native American knapping site. We had recently learned that there is no endemic obsidian in the high Siera, so that whenever you find it up there, you are seeing something that humans brought and left behind. So this was a place where Native Americans, Paleo-Indians as they are sometimes called, or the first people, had sat around, smacking blocks of obsidian maybe the size of bread loaves, using stone tools to knock off shards that they then knapped further, until they had arrowheads, spearheads, hand tools with cutting edges, and so on. There were so many shards under our feet that it had to have gone on like that for — who knows? Hundreds of years, it looked like. This place had been a human place for hundreds of years, you could see that just looking around.