Friday, May 25, 2007
So I’m gonna personalize the lesson for today and delve into what I’ve been working on so diligently. Let’s start with my research area: the lovely Cascadia Basin.Cascadia Basin is an underwater feature nestled in the North Pacific off the coast of Washington, Oregon and Canada. It’s pretty deep (~ 3000m) for not being so far offshore and it gets deeper as you move from the north to the south. As you can see from the map above, it’s cut by Cascadia Seachannel which runs north/south. You can think of seachannels as basically underwater canyons. HUMONGOUS canyons that make the Grand Canyon look like a baby.
If you’ve been with me from the beginning, which I think is only one person, you’ve read “Science Lesson #1: Oceanograph-me”. I told you a little bit about what I’m doing in this part of the ocean, but let me back up and explain things more thoroughly.
There is a shitload of the nutrient silica in this part of the world. Silica is what little phytoplankton called Diatoms use to make protective coatings called frustules. We like diatoms because they’re plants that can photosynthesize and wisk away some of the CO2 we are pumping into the atmosphere as we burn fossil fuel. Good guys. People like my advisor (and therefore me) want to know why there is all this silica in the North Pacific. Does it have to do with having a ton of diatoms, or is it because of something else?
There are two ways to get this much silica into the waters of the North Pacific. One way is to pump it through the oceanic crust via hydrothermal vents. You’ve all seen these things. They look like this:
Another way to get all this silica is by the dissolution of those diatom frustules as they fall through the water column. This is a two part process because not only does the silica dissolve as it makes it’s way to the seafloor, but whatever solid chunks make it to the seafloor continue to dissolve as they’re sitting around. Lots of biology = lots of silica.
How do we tell where our silica has come from? We look at another element called germanium. Hydrothermal vents pump out all sorts of chemicals, one of which is germanic acid (GeOH4). If you’ve got water that has been thru a hydrothermal vent, you’ve got yourself a ton of germanium. On the other hand, when diatoms make their little frustules, a little bit of germanium sneaks in there with the silica. Not much, but just a little.
What I do is jump on a big boat and collect water from all different depths within the basin. I take this water and analyze it for silica and germanium concentrations and then plot it up on a graph like this.
Looking at the picture, if we’ve got water with silica that is hydrothermally derived, the majority of our data points will cluster on a really steep line. If we’ve got water with silica that is from dissolution of diatoms, our points live on a much shallower line.
Sounds easy right? Oh, but that’s where you’re wrong! There’s so much nit-picking and number crunching and migraine inducing data reduction that goes on when you want to make a graph like this. Always remember that the first 4 letters of analytical chemist are ANAL. And I am tits deep in it, folks. Back to work!
*TM: Le Bomb
Wednesday, May 23, 2007
Advection is considered “Directed Velocity”. Just movin’ along in a straight line. How we describe advection is by flux. Advective flux is velocity (in meters/time) multiplied by Concentration (in moles/volume). The units of flux are moles/area-time.
Let me refresh your memory on what a “mole” is. A mole, in the chemistry realm, is a shitload of atoms (6.022 x 10^23 atoms to be exact). We can convert from moles to mass if we know an element’s atomic weight.
Look at our periodic table of the elements. See that number with a bunch of decimal places behind it? That’s the atomic mass. One mole of that element weights that many grams. For example, the atomic weight of Germanium is 72.59 so a mole of Germanium weights 72.59 grams. That’s 20.74 eightballs of Germanium to a mole. Don’t do drugs, kids.
Advection is a great way to describe stuff that is sinking. Diffusion on the other hand tells you about how things are spreading out. Diffusion is “Random Motion”. Remember that whenever you have a big glob of something that is really concentrated, like pee-pee in a swimming pool, it wants to move from an area of high concentration to low. We describe diffusion using Fick’s First Law.D stands for “diffusivity” and is in units of area per time. This law is also really great if you want to describe eddy transport. Eddies are big, swirly, chaotic regions of fluid movement. You can see them when you put cream in your coffee. The fluid mechanics within those eddies are hard to describe because the movement is so random, but the transport of particles via those eddies can be figured out using Fick’s first law.
Want to know more about this mysterious Fick? Adolf Eugen Fick was a 19th century
German physiologist who defined laws that we use for diffusion. He also invented the contact lens.
Kind of an intense lookin’ dude. It’s interesting that the man who invented the contact lens came up with laws that we use for Geochemistry. Laws that I will be grilled on during my Qualifying Exams. Thanks buddy.
Monday, May 21, 2007
Liquefaction happens when you take a bunch of unconsolidated (loose) sediments, like sand, get’em wet, and then shake the shit out of ‘em. Wet sand might be fine on its own, but once it’s shaken (like during an earthquake) the sand looses its resistance to shear stress and behaves like a fluid. As you can imagine, this causes a lot of problems in the realm of engineering and structural design. You might think “Well, no big deal. I’m sure structures are built to withstand this by sinking the foundation deep into the ground”. Unfortunately this is not the case around the world. The US enjoys pretty strict building codes and organizations that are paid to enforce them. Such is not the case in places that can’t afford to be as stringent about building safety or just don’t have the time to think about the buildings they live in.
This is what liquefaction does.
The picture above was taken after the Niigata Earthquake in 1964 (click here for a map). There was a magnitude 7.5 earthquake offshore that triggered a tsunami, but luckily the loss of human life was minimal. The apartment buildings in the picture are still totally intact, not much structural damage. Just tipped over. Kind of amazing, isn’t it?
Not all towns affected by liquefaction are that lucky. Just check out this newspaper illustration made after an earthquake struck Port Royal, Jamaica.
Port Royal was a popular pirate pit stop in the 17th century where debauchery reigned! I remember being told once that it was the inspiration for the port *his lordship* Johnny Depp puts together his crew of ruffians in the first Pirates of the Caribbean movie. It might as well have been, but don’t quote me on that. Anyways, the town was built on a sand spit and when an earthquake hit in 1692, a big chunk of the city literally sank into the ocean. During the shaking, the ground turned into sandy slurry and swallowed people up whole.
Warning! Stop reading if you are a squeemy baby! Probably the most horrifying part of all this is the people who were trapped in the sand once the shaking stopped. You see, without the shaking the sediments go back to normal, so anyone who had any part of their body trapped in the sand when it was liquid was crushed as it solidified. You probably can’t see it in the picture, but there are little people stuck in the ground and dogs eating the heads of the deceased. Gruesome!
So that’s liquefaction. What else is there to say about a process that swallows people whole and causes buildings to tip over? Liquefaction: the sporadic killer.
Friday, May 18, 2007
Soil is divided into five horizons:
O-horizon: O for organics. Lots of loose debris like dead leaves and dead asshole bees that will sting you even though they're dead.
A-horizon: The darker layer just below the O-horizon. Mixture of organics and sediment. Lots of live bugs.
B-horizon: More sediment than A-horizon. Lighter color, less organic material
C-horizon: Less of what we think of as “soil”, more weathered bedrock – bedrock being the super hard stuff that is way under the soil. Something like granite or slate or gneiss (see “Rocks for Jocks”)
R-horizon: Unweathered bedrock.
Soils are classified kinda like sedimentary rocks: according to their grain size. You’ve got fine stuff like clay and silt, then sand of various sizes, then gravel, cobble and finally boulders. What you do when you’re an engineer is construct a graph like this called a grading curve:
On your y-axis you have the % that passes thru a sieve of a particular size, also considered “percentage finer”. On your x-axis you’ve got grain size on a logarithmic scale (see "Science Lesson #4: MAGNITUDES! for a refresher on logarithims). Over on the left side of your x-axis you have itty-bitty grains like what would be in clays and silts. But as you move over to the right side of the x-axis you’ve got sediments the size of rocks and pebbles and the like.
Let's do a thought experiment: Say you’re in charge of classifying a soil that something big and important will be built on. Like a new burrito shop. How do you do it? Start by collecting a soil sample and running through a sieve that’s pretty porous (i.e. large holes). Drop the soil in the sieve and see how much comes out the bottom. If it’s a lot, meaning that your soil is relatively free of big rocks and pebbles, you say to yourself “this soil is 100% finer than the size of this sieve”. You move on to a smaller size sieve. About 80% of your sample comes out the bottom therefore 80% of your soils is finer than that sieve size. You keep doing this until you get to a sieve that is so fine none of your soil can get through. At that point you’ve got 0% finer and CONGRADULATIONS! You’ve constructed a grading curve.
Knowing what kind of soil you’re building on is important for a multitude of reasons. Moisture causes a lot of problems because certain types of clays start to behave like putty when they’re wet. Or you can get a soil that doesn’t compact very well or looses cohesion. Lots of engineering problems arise when you’re dealing with soil. Drainage, plumbing, septic tanks, gas and electrical lines are all things that you don’t want bad soil to muss up. So I guess soil is pretty important after all. Don’t ignore soil or soil will ignore you!*
* It pretty much does this already.
Wednesday, May 16, 2007
People like Al Gore have their hearts in the right place. He is being tutored in a very difficult subject by the very best minds in the field. He is a public figure and revered enough to garner the attention of the masses. And, come on, he was on Futurama so he’s awesome. Unfortunatley, some of the ideas he harps on have not been fully validated yet. I'm not saying that they won't be, it's just that some of his claims are a wee bit premature. For example: we get a lot of information from ice cores. Scientists take a slice of the core, look at the gas trapped in there, look at the isotopes in the water, and important implications follow thusly. Problem is that the gas and the ice are not the same age. It's really hard to get the precise age of that gas. There's all this hullabaloo right now about the claim that the rise in CO2 caused warming at the end of the last glacial or if warming started before the rise in CO2. It's a case of the chicken or the egg: warming then CO2, or CO2 then warming? Not clear just yet.
The Earth is warming, that’s a fact. The heart of the matter is whether or not we’re experiencing warming solely due to our own actions or if there are other natural processes involved. Like Milankovitch cycles. The Earth is very special planet and has gone through some dramatic periods of warming and cooling. What we forget is that humans have been around for climate change already, like during the Medieval Warm Period where the ice sheet on Greenland melted just enough so the Vikings could settle there and have agriculture. That didn’t last too long, and eventually the ice came back which made Greenland not that enticing, even to Vikings.
To bring this all home: there’s probably little, if anything, we can do now to halt the effects of all the greenhouse gasses we’ve been pumping into the atmosphere. The Earth will change, but like always humans will adapt. Unfortunately the folks at the bottom are going to get the shit end of the stick, like always. Developing nations will have more and more problems with water supply and it will be very sad because more well off countries probably won’t do much in the way of helping out. The world itself will be fine. Humans will just end up being a messy blip in geologic time. And then in a few billion years when the sun expands and obliterates the planet, it won’t really matter will it?
Monday, May 14, 2007
Milankovitch was a Serbian engineer and mathematician who put together a theory about why the Earth goes thru cycles of glacials and interglacials. You see, nobody knows why the Earth has these long, cold periods called glacials. Finding out why the Earth goes thru these hot and cold periods is a big deal to researchers right now since we’re faced with the looming possibility of total climate annihilation!
To better predict the future, climatologists are looking at the past. The last glacial ended less than 20,000 years ago, which isn’t very long in geologic time. During glacial times is when we had awesome beasts like mastodons and saber tooth tigers, but unfortunately it provided the premise for the movie “Ice Age” and therefore contributed to the salary of John Leguizamo.
Milankovitch proposed that we get cycles of glacials and interglacials because of the Earth’s orbit with respect to the sun. We have 3 flavors of variation:
1.) Eccentricity – has to do with how elliptical the earths orbit is. Sometimes the Earth’s orbit around the sun is more circular than at other times. Further from the sun = less solar energy = colder. Eccentricity varies on a 100,000 year time scale.
2.) Obliquity – the Earth is tilted a little bit on its axis. Sometimes the Earth sits more up and down, but sometimes it’s more slanted. Obliquity varies on a 40,000 year time scale.
3.) Precession – imagine a top spinning around. Or a dradle (ooooo! I went there) You get a little bit of wobble as it spins around. The Earth does that too and the wobbling is called precession. This process affects the Earth’s orbit on a time scale of about 20,000 years.
Problem is that none of these mechanisms fit perfectly with the records of past glacial and interglacial cycles. It’s not like every 40,000 years and BOOM! The Earth gets super cold. Glacials happen because of a combination of factors, a combination that will make someone rich when they figure it out. But Milankovitch theory has not been totally poo-pooed yet, it’s still got its valid points. So props to Milankovitch, even though I’m totally sick to death of hearing about him.
Tuesday, May 8, 2007
Friday, May 4, 2007
The instructor gave us an assignment that is broad and meandering, which totally blows, but I think I've got an idea that will win him over. Let's discuss it, shall we?
More and more studies are coming out saying that warming around Antarctica happened BEFORE the rise in carbon dioxide after the last glacial (in your face, Al Gore!). If this were the case, we should be able to use tracers of sea-ice coverage around Antarctica to get a time frame of when all this warming happened and compare it to the rise in atmospheric CO2. Antarctica was covered with even more ice than it is now during the last glacial. This ice extended way up north of the actual continent and into the South Seas.
If you cap off the ocean around Antarctica with sea-ice, like during a glacial, you screw with the ocean’s ability to exchange gases with the atmosphere. Gases like carbon dioxide. As we come out of the glacial, the world starts to warm and this sea ice will start to melt. We would like to know the timing of the melting of this ice and compare it to the timing of the increase in atmospheric CO2. One way to tell the timing of this melting is that as the sea-ice melted, it dumped a lot of crap onto the seafloor. Crap that includes the tests of specific diatoms. These diatoms are WAY different than the regular diatoms that live in the salt water. If you can get a sediment core, look at how much of these sea-ice diatoms are present at any given time AND when they disappear, you should be able to make some fantastic claim about the presence of ice around Antarctica. Ta-Da!
Sidenote! Doesn't Antarctica look like a smiling rhinocerous? Now you'll never forget how to draw this, our most neglected continent.
Cornfused? Me too. But somehow or another I’ve gotta sort this out before Tuesday. I'm so fucked.
Wednesday, May 2, 2007
If we look at the picture below, we’ll see that ocean ridges wrap around the globe like the seams on a baseball. They are areas of divergence meaning that they’re spots where our plates are moving apart from one another. If we look close up at an ocean ridge we can see the effects of all this pulling apart (see below). We’ve got Normal Faults because we’ve got extension in the crust. In the very very middle of the ridge (the ridge “axis”) we’ve got kind of a saggy region which is called the Rift Valley. If you were to find yourself in either Iceland or East Africa, you could see an actual Rift Valley. Touch it. Walk through it even.
Magnetic Field? What the shit?
The Earth’s magnetic field undergoes reversals every now-and-again. The reversals are far from periodic and lots of people worry about why and how they reverse in the first place. Sea floor rocks like basalt are created at the ridge axis. Basalt has a lot of iron in it (see "Rocks for Jocks"). When the hot magma hits the cold water, little bits of iron minerals align themselves in the orientation of the Earth’s magnetic field (like a teeny-weeny compasses). By investigating the orientation of those compasses we can learn when the reversals happened and how long they lasted.
I wish I could say that a magnetic reversal means something exciting will happen like fish turn into cheeseburgers or the sky turns pink, but aside from messing with a few birds nothing really crazy happens. Sorry, gang.