The thrust belt in my driveway

It's snowed a lot in the past two weeks. Somewhere around two feet of snow fell between the last day of classes and December 26. Good for ski areas, but a lot of work to shovel. Fortunately, structural geology can make all kinds of difficult labor fascinating.

When you push a shovel through a relatively thin layer of snow, it piles up next to the shovel in a wedge shape. Push the shovel along, and the wedge gets longer and thicker, but it maintains the same shape: a triangular wedge, with a consistent angle at its front end.

Photo: a wedge of folded and faulted snow in my driveway, 12/22/08.


You see similar shapes in belts of thrust-faulted rocks from mountain belts all around the world, from the Himalayas to the Canadian Rockies to the Appalachians to Taiwan:

The cross-section above is from a classic paper by Davis, Suppe, and Dahlgren (1983) that explains what's going on mechanically in these wedges. The shape of the wedge is governed by a balance of horizontal forces: the push from behind the wedge; gravity, which would tend to flatten out the wedge (by moving material from the higher back part of the wedge to the front); and the frictional resistance to sliding, which tends to keep the front of the wedge from sliding along, causing the wedge to be steeper. The other big assumption is that the wedge is always just about to fail: its internal strength exactly balances the stresses that compress it. This means that the nature of the material also makes a difference - cohesive sheets of material behave differently from loose sand.

There's a lot of underlying math behind the explanation of wedge mechanics, but the cool thing about it is that it all boils down to a pretty simple concept. If the friction at the base of the wedge and the mechanical behavior of the rock (or snow) stays the same, the wedge should maintain the same shape. It can get bigger, but the front of the wedge should keep the same angle. That simple geometry has a lot of predictive power. It tells what should happen in a mountain belt that's eroded by a lot of rain or glaciers, compared to one that's in a rain shadow. It's been used as one explanation for the exhumation of high-pressure metamorphic rocks. And it solved a long-standing problem for structural geology: how could huge masses of rocks slide along a nearly flat plane for immense distances, as had been observed in places like the Canadian Rockies.

And it turns snow shoveling into an analog modeling experiment. Take a driveway made of smooth concrete. Drive a truck over it, and pack down snow in parallel ridges. Then let it snow another couple inches before shoveling the driveway. The results of the experiment look like this:


The wedge started out small. It's hard to see the exact structure forming - are there thrust faults beneath the folds on that surface? But it formed a nice taper, and slid along fairly easily. (Note the highly rigorous descriptions of basal friction from this experiment.)

I pushed the shovel a bit more, and the wedge got longer and thicker, but kept the same shape:


But then I reached the old tire track, and it suddenly got really hard to push that shovel. And the wedge looked like this:


The taper of the wedge suddenly got steeper, at least until I got past the tire track. But by that time I was experiencing significant edge effects, both from the top of the shovel and the snowbank beside the driveway, so the experiment ended.

The different snow storms led to somewhat different wedge shapes. Over Thanksgiving, we had a couple inches of wet snow. It formed a cohesive layer, and I could see the individual fault blocks. (I even had some tear faults separating thrust faults with different offset! Unfortunately, I didn't have the camera yet.) Before AGU, we had an inch or so of powder, which compacted somewhat when I shoveled it. And on Christmas night, we had about five inches of wet, heavy snow, and I stopped doing experiments because moving it was a lot of work, and besides, it kept falling over the top of my shovel.

My students still think that snow is for skiing, not for experimenting with structural geology. But if you've got to shovel, you might as well have geeky fun at the same time.

Reference: Davis, D., Suppe, J., and Dahlgren, F. A., 1983, Mechanics of fold-and-thrust belts and accretionary wedges: Journal of Geophysical Research, v. 88, n. B2, p. 1153-1172.

Photo note: I adjusted the levels on all the snow photos, because I haven't figured out how to take good photos of snow with my new camera yet.

Wait! Field season isn't done yet!

Well, actually, I guess it probably is for this year:

(image deleted, because I screwed up my saving and linking)

There are two inches of snow on the ground. (I would take a picture, but I still don't have a camera.) Total daytime accumulation of 1-3 inches is expected, according to the National Weather Service. More snow possible tonight and tomorrow morning, and a mixture of rain and snow tomorrow afternoon.

Yay!

Except my mapping class is still mapping. And some of them didn't start the most recent map, because they were voting last week.

The high temperatures are supposed to be above freezing today and tomorrow, so maybe it will all melt down here. Or maybe I'll need to go into the field next week, and talk about the cross-sections and the report this week (before some people have done their mapping).

I would make jokes about global warming going away, but someone would probably take them seriously. (Snow in late October or early November isn't that unusual here at 7000 feet.)

Gustav and uncertainty

I'm watching the forecasts for Tropical Storm Gustav with dread.


Image: five-day track forecast for Gustav, from NOAA.

Three years ago this week, I began my first Earth Systems Science lecture with an image of a swirling cloud looming over the Gulf of Mexico. On the second day of class, I was asking students if they knew anyone from New Orleans, and whether they were all right. It was horrifying, particularly because I had used the geology of New Orleans as an example in classes for years, ever since I read The Control of Nature.

But even though Gustav appears to be headed on the absolute worst course for the city of jazz, levees, and elevations below sea level, Forecaster Franklin of the National Hurricane Center added this reminder to the end of Wednesday's 11 pm discussion:

IT PROBABLY WOULDN'T HURT TO REMIND EVERYONE THAT THE AVERAGE 5-DAY OFFICIAL TRACK ERROR IS ABOUT 300 MILES...AND THE AVERAGE 5-DAY INTENSITY ERROR IS ABOUT 25 MPH.

Error. In other words: there are reasonable odds that we'll be wrong, and the storm will hit Houston or the Florida Panhandle.

I'm not a statistician. In fact, I've never taken a statistics class. (I'm embarrassed enough to have bought an undergrad statistics textbook, but not shamed enough to have buckled down and worked through it.) But I am a scientist and a teacher, and that means that I need to somehow get students thinking about uncertainty.

I'm not a weather modeler, so I think about uncertainties more in the context of measurements than of predictions. I learned about the concepts of accuracy and precision in chemistry classes, and about error estimates in intro physics. My geology classes never took on the topic directly. But it should be possible to think about the ideas in geology, as well. How good is that bearing you measured on your compass? When should I count your answer as "wrong" - when it's half a degree from mine? One degree? Five degrees? Even if you weren't balancing on a cliff with shaking hands, would our measurements always be identical? When I talk about uncertainty in class, it's usually in that context.

Uncertainty in weather models is something I know less about. I know, from reading the discussion of the hurricane forecasters, that they look at the predictions of a number of different models (which presumably use different ways to weigh the effects of wind shear and warm Gulf water and other weather systems). I don't know where the 300 mile uncertainty comes from. (Is it the same kind of sense based on experience as I have about the correctness of my compass measurements? Or is there a more formal statistical way to derive the model's uncertainty?)

I hope that Gustav does not become a teachable moment. May the predictions be wrong, and may the storm weaken. And may everyone be prepared, in the event that it is correct.

Flaky weather

On Tuesday, temperatures were in the 80's Fahrenheit. It cooled off Wednesday, and today, it did this:



It started snowing on Wednesday in the high country, which may explain the hydrograph for the Animas River:



(Image source: USGS Water Watch)

I was talking to one of my colleagues about the daily peaks: notice that they were always before noon. (Compare it to the gage height graph from Ouray, posted at Geology Happens for this month's Accretionary Wedge.) And the peak discharge was on Wednesday, when it started cooling off.

My colleague reminded me that the Animas has a long way to go from the high country. Nobody rafts all the way from Silverton to Durango - there's an impossible-to-run section deep in the canyon, clogged with logs, certain death to even the most skilled kayaker - but he had a good sense of how long it takes to get through town at high water. It made sense that the water might take around 16 to 20 hours to make it down to Durango. That would explain the morning peaks, and also the highest discharge on the day it started to cool.

And the diurnal fluctuations have disappeared. The snow is currently accumulating again, up to a foot and a half of snow predicted in the high country this weekend. I hope for the sake of the soon-to-arrive field camps that it melts quickly. Though the water managers may have different wishes.

Watching the Mississippi basin

Has anyone else been watching the USGS flood map this spring?

This is what it looks like today, April 10.



There are at least three things that scare me on this map.

1) All those black triangles represent places where the rivers are above flood stage. Look how many of them there are!

2) Some of the places above flood stage include the Mississippi River at Baton Rouge and the Atchafalaya River at Morgan City. (Recommended background reading: "Atchafalaya" in The Control of Nature by John McPhee. For anyone who hasn't read it: the Atchafalaya River would probably be the main course of the Mississippi River by now, if it weren't for some massive engineering. The Old River Control Structure, which tries to let just enough water into the Atchafalaya to prevent floods in Baton Rouge and New Orleans, nearly failed in the 70's. It's been strengthened since then, but it hasn't faced huge floods, either.) Both places have been a few feet above flood stage for a week, at least.

3) Of the big tributaries of the lower Mississippi, only the Ohio is currently above flood stage. But it's still snowing across the Rockies, the northern plains, and Minnesota:



The Missouri and upper Mississippi drain areas where the snow hasn't melted yet.

I was frantically writing my dissertation in 1993, and water data wasn't on the web for daily ogling. I remember some discussion that the 1993 floods on the upper Mississippi and Missouri didn't result in danger for Louisiana because the Ohio basin was fairly dry that summer.

I hope the Ohio goes down before the Missouri and upper Mississippi rise.

Edit: The National Weather Service flood warning for Natchez, Mississippi (above the Old River Control Structure) says the Mississippi should crest just below the level of floods in 1983:

THE FLOOD WARNING CONTINUES FOR THE MISSISSIPPI RIVER AT NATCHEZ
* UNTIL FURTHER NOTICE...OR UNTIL THE WARNING IS CANCELLED.
* AT 8:00 PM WEDNESDAY THE STAGE WAS 54.4 FEET.
* MODERATE FLOODING IS OCCURRING AND MODERATE FLOODING IS FORECAST.
* FLOOD STAGE IS 48.0 FEET.
* FORECAST...THE RIVER WILL CONTINUE RISING TO NEAR 55.5 FEET BY
TUESDAY MORNING.
* IMPACT...AT 55.0 FEET...FORT ADAMS POND ROAD IS FLOODED.
* FLOOD HISTORY...THIS CREST COMPARES TO A PREVIOUS CREST OF 55.7
FEET ON MAY 31 1983.

According to John McPhee (Control of Nature, p. 53), the 1983 flood was the 3rd largest of the 20th century. (1973 was the year the Old River Control Structure nearly failed.)

Hmm... what's up with the jet stream?

It snowed on our winter festival this year.

It never snows on the winter festival. Ever since I've moved here, it's been the big joke in town: at the end of January, right at the time of the winter festival, the snow will all melt. And when La Nina kicked into gear this fall, season passes at the ski area seemed like a really bad idea.

We were wrong. We've had a good three feet of snow at the foot of the mountains, and up high, on the Continental Divide, there's a lot more. Good news for skiers and for places that rely on water from the Colorado and Rio Grande. Not such good news for geology field trips (though my classes, for some reason, are not complaining).

So what's going on?

We're on the south side of a mountain range that has several 14,000 foot peaks, and that averages 10,000 feet in elevation. That means that we get rather strange orographic effects: in order to get big dumps, we need our air to come from the southwest, from San Diego or Baja, rather than directly from the west. And this year, when we've had the big storms, the jet stream has done this:



(Source: San Francisco State University/California Regional Weather Server.)

When it gets to the Pacific, the jet stream makes this big loop north, sometimes all the way to the Bering Sea, and then goes almost straight south again, down to the Mexican border, and then shoots back north again... right over us. Over the course of a few days, the entire pattern shifts eastward, so later in the same week, there's a big loop from Alberta down to the Gulf of Mexico and back up the East Coast to the Canadian Maritimes.

Now, I've been hearing about the jet stream for years, and even though I briefly touch on it in my intro earth science course, I don't fully understand it. The jet stream is a region of strong winds high in the troposphere (the bottom layer of the atmosphere), and is caused by temperature differences between the tropics and the poles. The temperature differences create pressure differences (because warm air is less dense than cold air, and less dense air rises), and the addition of the Coriolis effect means that the winds blow mostly in big circles around the globe. "Mostly," that is, because there are also waves in the jet stream (called "Rossby waves"), and their movement around the globe creates troughs and ridges that, in turn, create low and high pressure systems.

But why are the Rossby waves so big this winter? And, if this is a typical La Nina pattern, why didn't it happen last time there was a La Nina event? (La Nina events have colder than normal water in the eastern Pacific, and warmer than normal water in the western Pacific, and strong east-to-west trade winds. And they're traditionally associated with dry winters in the Southwest. I've always explained that pattern by invoking the lower evaporation of colder water over the Pacific, but perhaps I've understood it wrong all along.) And why do the big Rossby waves seem to develop over the Pacific - the winds through Asia are fast and strong and mostly west-to-east, but when the big storms develop here, the winds start looping way north and south across the Pacific.

How do ocean temperatures affect the development of these big waves in the jet stream? Does it have anything to do with ocean surface temperatures in the Bering Sea? How far south is the sea ice this winter, for that matter? Is this some of the stuff that's so hard to model in global climate models?

And is it going to dump snow on me again on Monday? I've run out of indoor things for the intro class to do.

And they won't be covering weather until the end of the semester.

(For the Accretionary Wedge, February 2008: "Things that make you go hmmmmmmm.")

In which climate and weather are not the same thing...

It's a good thing that I'm not teaching Earth Systems Science this semester, and don't have to deal with the inevitable questions about whether this winter disproves global warming.

Here's the view from my house yesterday.



Hobbit Four-year-old for scale. If you look closely. See that red hood kind of sticking up out of the snow fort? That's him.

Classes were cancelled today, so that the college could plow parking lots and remove dangerous snow from roofs. I suspect, though, that today will go down in college legend as the Official Powder Day.

Meanwhile, there was an avalanche on the south end of town this afternoon. And I have the urge to make my structure class calculate the shear and normal stresses acting on the roof over their heads...

Power-less

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1025 AM MST MON JAN 7 2008

...ONE MORE ROUND OF HEAVY SNOW FOR SOUTHWEST COLORADO AND HEAVY
SNOW EXPECTED FOR EXTREME SOUTHEAST COLORADO...

.HEAVY SNOW WILL INCREASE FROM EXTREME SOUTHEAST UTAH INTO
SOUTHWEST COLORADO. SNOW WILL BE HEAVY AT TIMES THIS AFTERNOON
BEFORE TAPERING OFF IN THE EVENING. VALLEY AREAS OF EXTREME
SOUTHEAST UTAH AND SOUTHWEST COLORADO WILL RECEIVE ANOTHER 4 TO 8
INCHES TODAY AND THIS EVENING. NEW SNOW IN THE SAN JUAN FOOTHILLS
COULD PICK UP ANOTHER 8 TO 12 INCHES.

We've already had a foot and a half of snow at my house (less than half the accumulation at Purgatory, in case you're interested in skiing when the passes open). It's wet and heavy, and the beetle-damaged trees aren't taking it very well. I haven't had electricity since Saturday evening (which means, most importantly, no water - though it also means no internet). I would like to blog more about it, but it's the first day of classes, and I need to teach a topo maps lab (to the students who made it to town), and then go home and hibernate some more.

I hope Ron is doing all right with his southwestern photography expedition. If you read this, Ron: this is not a good time to take photos of rocks around Durango. :D

Teaching: thinking globally, observing locally

Yesterday morning, the National Weather Service issued a blizzard warning for my local mountains. It was the perfect set-up for a winter storm: a storm off the coast of Baja California, a jet stream that looped way down to Baja, and then up across central Arizona and straight for our mountains. I was on my next-to-last day discussing weather in my intro class, and it made for a perfect discussion. We could talk about winds, about low and high pressure, about the role of the mountains in controlling the weather in Durango and Denver.

The students were attentive and engaged, in the way that’s only possible when the professor is discussing the possibility of a powder day with a class full of skiers.

And then it fizzled.

It’s been raining. Raining hard. The temperature has stayed in the mid-30’s (F), even through last night. If it had been just a few degrees colder, there would be more than a foot of snow on the ground. But even though it has cooled a bit this afternoon, and there are now some big, fluffy flakes in the air, the snow isn’t sticking. I can see where the snow line probably is: there’s a layer of low clouds around 8000 feet, and that’s where the NWS is currently predicting the snow accumulation stops.

I only live at the edge of the mountains, and the ski area reportedly has two feet of fresh snow, and expects at least another foot. So the students won’t be disappointed.

But the lack of snow down here is important. Snow stays on the ground for months, and a lot of the water soaks into the ground. Rain runs off. And the cold and the snow help the pinyons and the Ponderosas fight off the bark beetles that have been killing the trees and making the summer fire hazards that much worse.

One storm doesn’t mean much. But changes in the snow level are one of the predictions of climate scientists like Jonathan Overpeck (who spoke here a couple years ago). And on Monday I’m talking about climate. So: do I use this storm as an example?

In some ways, that would be a very dangerous thing to do. Many people confuse climate with weather, and assume that if a winter is snowy, or a summer is cool, or a hurricane season is less active than expected, then global warming has turned out to be wrong. But weather and climate are not the same thing: weather is local and short-term; climate is regional or global, and deals with longer-term trends.

On the other hand, global climate can seem distant and irrelevant. Even with CNN and the internet and Google Earth exercises, it’s easier to care about things in one’s own backyard. One of the successes of An Inconvenient Truth, in my opinion, was the way it took a global scientific issue and made it personal, made it worth caring about.

So. Should I use the local weather as an example, and risk students walking out of class convinced that a single storm is what confirms or denies the existence of global warming? Or should I stick with discussing evidence that has been peer-reviewed by specialists, and remember that I’m professionally a structural geologist, not a meteorologist, and I am probably missing some crucial explanation for why this storm appears to be fizzling out, at least at my elevation?

(As I write, of course, the snow has begun to stick. Maybe we’ll get something out of this one after all.)

Teaching: more on weather journals

John Fleck asked for more info about my weather journal exercise. Here it is.

Every semester, I end Earth Systems Science by talking about weather and climate, and instead of giving quizzes, I make the students keep a weather journal.

Here's what I ask them to do:

1. (3 points) Keep a journal of the weather that occurs for the next three weeks. Every day, record:

➢ maximum and minimum temperatures (temperatures at Durango airport are available from the National Weather Service)
➢ clouds -- how much of the sky is covered (as a percent), what types of clouds are present
➢ precipitation -- does any occur? In what form (rain, drizzle, snow, hail, etc.)? Is it continuous in time or space, or does it occur as showers? How much falls?
➢ wind -- speed (qualitatively) and direction
➢ any other interesting phenomena

Detailed weather observations from the Durango airport are available at http://weather.noaa.gov/weather/current/KDRO.html . You may use the NOAA observations as a source, but I would also like you to include your own observations.

2. (2 points) Explain the weather patterns you observed. Check out weather discussions at the National Weather Service web site (http://www.nws.noaa.gov/) for information about national and global weather patterns.

Why do I do it that way? Well, mostly because that's what I brainstormed the first time I taught the class. But I wanted to create an assignment that would get the students to look at the world around them, and think about what they were learning in class, and connect them together. So when they wake up in the morning and see this:



... they have some idea why there is frost on the car windows but not on the house windows (as was the case at my house on Saturday). Or so, when the smoke from the Durango-Silverton train hangs down in the valley on a cold morning, they realize that they're seeing a temperature inversion.

And I didn't want to make the assignment too complicated - I didn't want them to need access to a barometer, or for them to get up in the middle of the night to measure the temperature.

So does it work? Well, it's hard to say. A few students make great, detailed observations. Other students do the bare minimum. And it seems like it's pretty hard to connect the local observations to bigger picture questions - I would need to have them look at the National Weather Service web site daily, or something.

I also hope that the weather journals will give me some concrete examples of things to discuss in class. I started class this morning (on humidity and the dew point and ways that clouds form) with a picture of frost on my car, and we talked about that (and about the experiences of students who have grown up in more humid climates with a lot of dew). We still didn't end up talking about some of the more interesting things I saw over the weekend, such as the fog that formed at dusk on Friday, after the sun had started sublimating the new snow. (I think - though I'm not certain - that I was seeing something like the crazy freezing fog that Albuquerque had last winter, when the snow sublimated and raised the relative humidity near the ground, and then the cold air near the ground condensed it into fog.)

This morning, however, I asked how many students had described frost in their weather journals. Only a couple students raised their hands. So it doesn't seem like most of them are paying very close attention. They've got a few more days, though, so maybe their observations will improve.

Teaching: understanding graphs

Do you remember when you first learned to read a graph?

I don't. And that might be a problem for teaching.

I'm not talking about the various weird graphs that geologists use. (Stereonets, Ar release spectra, U-Pb concordia plots, ternary phase diagrams... ) I'm talking about a nice, straightforward, x-y plot. Two dimensions, commonplace variables like temperature and time, no logarithmic scales or ratios between variables or anything like that.

(Image source: Global Warming Art)
I started thinking about this while explaining a weather journal assignment to my Earth Systems Science class. I cover weather and climate at the end of the semester, in the slot that always gets shorted when I run out of time. But I figure that weather is something that the students ought to be able to observe, at least qualitatively, and I want to give them a reason to read the book and think about it, even when I don't get to all the material in class. So I have them keep a weather journal: every day they have to record temperatures, cloudiness, precipitation, wind direction, and anything they find interesting. The goal isn't to teach them how to professionally record weather observations - the goal is to get them to observe the world around them and relate what they see to the explanations from their book.

This year, I lost nearly an entire class because the students asked one good question: when, and where, and how, should they make their observations?

It's always a bit dangerous when students ask a good question that I don't have a canned answer for. They get to see me think on my feet - not always a pretty sight. And this time, to try to explain my thinking (and perhaps inspired by reading graphical arguments on Tamino’s blog), I started drawing a graph.

It wasn't a very good graph - it was qualitative, illustrative of an idea rather than a compilation of data. But it showed (maybe) what I was trying to illustrate: that temperatures vary throughout the day, so perhaps they should describe their observations qualitatively, and then look at the National Weather Service official maximum and minimum daily temperatures for comparison from one day to another.

I don't know whether the graph made sense to the students or not - I don't have a good technique for quickly assessing whether students understand what I'm saying. I’ve recently learned that graphs don’t make immediate, intuitive sense to a lot of people, and I didn’t take the time to slowly explain what I was showing them. If the graph made sense, then the discussion might have been effective – I asked the class to tell me how the temperature should change throughout the day, and built the graph pretty slowly, so I hope they thought through the problem with me. But if they didn’t understand the graph... well, I might as well have been lecturing in Klingon.

So I’ve been thinking about what I could do to improve their graph comprehension (and to assess whether I’m doing it effectively). The weather journal assignment might be a good place to start – it should be relatively easy for them to graph the daily minimum and maximum temperatures over these three weeks. I wonder if they could use the graph to look at other things – maybe qualitatively annotate the graph with wind direction, wind speed, precipitation, types of clouds, so they could look for patterns? (It seems like that is one of the uses of graphs: they show patterns.)

But when I start thinking about what to make them graph, maybe I’m getting away from the point. What kinds of activities help them really understand what they’re doing?

- Does it help to graph points by hand, or is that simply tedious and frustrating?

- Does it help to graph data they’ve collected, or data related to things they’ve experienced, so the numbers are associated with what they measure?

- How much data is enough, and how much is too much? It seems as though there might be a balance between having enough data to see a pattern, and having so much data that the exercise becomes tedious. (If the students graph data from a spreadsheet, the tedium disappears... but the kinesthetic experience of plotting the dots, and the spatial sense that comes with it, might diminish.)

- If I ask questions about the graph, how do I avoid mistakenly teaching them that correlation = causation? Or is it ok to first see that correlation can help one to figure out causation, and then explain the fallacy?

- Are they going to be too burned out after Thanksgiving to handle an addition to their assignment?

(Side note: there’s a project in the works at SERC to create online modules to give math practice to students in introductory courses. Graph-reading is one concept that the developers may add. If you’ve got math concepts that you need geoscience students to understand, take the survey for the project.)

Let it snow!

Here's the National Weather Service's forecast for my county for tonight:

SOME SNOWFALL IS ALSO EXPECTED OVERNIGHT ACROSS THE HIGHER MOUNTAINS...WITH SNOW LEVELS DROPPING TO AROUND 10000 FEET BY MORNING. ACCUMULATIONS OF 1 TO 3 INCHES WILL BE POSSIBLE ACROSS THE HIGHER PEAKS BY EARLY SUNDAY MORNING.

Thought #1: Yay! Must remember to grab camera when it clears. Maybe I'll be lucky and have the first clear day be Tuesday, when I'm going to be on a ridge with a view, teaching students to map.

Thought #2: On the other hand:

COLDER AIR MOVING INTO THE AREA WILL RESULTING IN SOME SNOW ACCUMULATIONS ABOVE THE 7000 FOOT LEVEL IN THE NORTHERN MOUNTAINS AND 8000 TO 9000 FOOT LEVEL IN THE SOUTHERN MOUNTAINS.

Well, I think the field area is below 8000 feet...

Thought #3: I love teaching in a science where I occasionally have to scrap a lab because of an early snow storm. :D And where my "work shoes" are Montrail Hard Rocks.

Edit: Oh, and Thought #4: Today is the equinox. Happy fall to those in the northern hemisphere, and happy spring to everyone in the southern hemisphere! (That goes double for Alessia in Antarctica.)

And Thought #5: I hope this storm's most intense rainfall is hitting north of the Four Corners, and Brian's field trip to the Guadalupes hasn't suddenly turned miserable. Rain is good... unless you're in a tent. Or are trying to get across flashy streams.

spectacular volcanic eruption photo

An amazing photo of the volcano Tungurahua (in Ecuador) was posted as today's Astronomy Picture of the Day. (I'm going to link rather than posting the picture; the picture is copyrighted.) You can see lava flows pouring down in all directions, and a blast of dark tephra blowing off to the side. You can see the prevailing wind direction on the photo, too: the wispy clouds (almost lenticular?) are typical of clouds on the windward side of a peak, and there is a little snow on the windward side, as well.

The photo was taken by Patrick Taschler, who has other really beautiful photos of the eruption animated on the front page of his site.

thinking of Jamaica

I visited Jamaica once, over twenty years ago. It was my first time outside North America, and my first time to the tropics. I remember green mountains, and waterfalls, and a winding road, and tiny run-down houses perched on the mountainsides.

I'm thinking of Jamaica tonight.



Hang in there, Jamaica.

Hurricane Flossy (or: in which correlation is not causation)

This is the current predicted track for Hurricane Flossy:



My first reaction was: "oh, good - it looks like the 5-day cone doesn't include Hawaii any more."

My second reaction was: "wow, the predicted track is almost parallel to the trend of the Hawaiian/Emperor seamount chain! That means it's almost the same as the motion of the Pacific plate!"

Lessons from this:

1) Sometimes people see what they're trained to look for, even when there isn't a good reason to see it.

2) I, for example, teach plate tectonics way too much.

Though I am tempted to make up a reason why a hurricane storm surge would make an earthquake on the Big Island more likely. I don't know if the reason would be valid, though - my explanation would have to do with pore fluid pressure, but I doubt that the little extra weight of water from a storm surge would make a difference for an earthquake that occurs at a depth of 17 km. (I'm also not sure why there's a thrust focal mechanism for the earthquake. It's interesting to speculate about, though.)

nitpicking the media: of swamp coolers and heat waves

The West has been hot. Hot, hot, hot. Well, except for here; our July weather pattern arrived on Wednesday, and we're having these amazing afternoon thunderstorms. (Well, amazing for now; I'm doing lab work this week.)

In any case, when I saw CNN's headline about the weather (Stifling heat spreads throughout West), I had to check it out and see which West, exactly, was miserable.

As I read the story, this section stood out:

Air conditioners -- and even swamp coolers -- were predictably hot sellers at the hardware store.

"I'm telling you, it has been nuts," said Dennis VanDyke, a manager at Power Townsend in Helena. "The only thing I am getting calls for is air conditioners."

VanDyke said some people prefer swamp coolers, which use a fan and the condensation of water to cool the air, over the more power-hungry air conditioning units.

Ok. Let the nitpicking begin. Key point: it's the evaporation of water, not its condensation, that cools things off. It's all about latent heat: it takes energy to turn liquid water into water vapor, and as the energy gets sucked off to send those water molecules flying away, the surroundings cool. This is actually an important concept. It explains why 90 F is pleasant here and unbearable in New Orleans. It explains why exercise is more pleasant in an arid climate. And it explains very important things, like why hurricanes cool the ocean that feeds them.

What's weirder and more confusing is that condensation actually does the opposite: it warms its surroundings. This seems counterintuitive, especially for people like me who grew up in cold, humid places, and who know how cold dew can feel on the grass (or - shiver - on a tent). But the condensation of water to make clouds heats the air, high up, and can make rising air continue to rise.

So, anyway: CNN, you lose points. Sorry.

Second point: swamp coolers are really, umm, cool. They cool a house by evaporating water - that's it. They use a lot less energy than air conditioners do. They aren't an option for places with high humidity, but in a place where the humidity is often less than 10%, they're great. (I don't have one - I cool my house by keeping shades pulled during the day, and opening windows at night. But I think they're a great concept. Good way to reduce electricity bills, reduce one's carbon footprint, and so forth.)

(Aside: I think I might keep track of little errors in the media. They might make fun exam questions.)