Introduction

Post date: Jul 6, 2013 5:30:08 PM

Orientation Day:

All of the internship students, who consisted of mostly incoming high school students met at a building (forgot the name, oops) and played some name games, looked at some cool rocks, and ate free food.

Afterward, I set up times with Matthew Malkowski, my mentor / partner / whatever-it's-called to meet. (Yay, no set schedule!) He's chill. He said that he partied too much in college, but here he is working on his PhD at Stanford. As I remember it, his work concerned the sediments here in California and some rocks down in Patagonia @ the tip of South America. He is going to analyze both of those locations for 2 different purposes. For Patagonia, it is to find something related to the geology some millions of years ago. For California, he is testing some methods of analysis to see whether those methods will work on the Patagonia samples. He is using Chemical Composition & Radioactive-Dating

Chemical Composition

To find the chemical composition of some sediment........................................... is an irritating process.

Here's a picture of what needs to be analyzed:

http://ocw.mit.edu/ans7870/12/12.110/labs/lab2/images/32.jpg

It looks plain and boring, like you could take one step out of your house and just pick a sample right out of the ground. These sediment samples needed to be sieved for all the particles < 63 um. What are these particles called? It's called Clay. Here's a visual explanation of particle sizes.

Because of the small size of the Clay, the sediment tended to clump together and refuse to sieve through the 63 um fabric. So we had to Wet-Sieve by trickling water through the sediment. Each sample took about 90 minutes to sieve, all for a bottle of dirty water full of Clay (and nothing larger). With about 10 samples, it took a long time. After that, Matthew and I waited for the Clay to settle, pouring out some of the topwater during the wait to remove some of the Organic stuff.

After finishing these up, Matthew's going to send the dried clay to some-place-in-Washington-whose-name-I-forgot. This place has a machine that does some analysis on these samples by melting them into its elements (like Chromium, Nickel, Manganese) and separating them by weight. That's when the Organic stuff that is still in the water evaporates and causes a horrible effect called LOI or Loss On Ignition. Having a Loss On Ignition of > 15% is looked down upon. Basically it's saying the data's unreliable and would look silly on Matthew's PhD paper.

After that, the guys at some-place-in-Washington-whose-name-I-forgot will send Matthew an Excel file with its Element Composition. So there are some Major elements like Vanadium, Chromium, Nickel. There are also some trace elements like Zirconium and Uranium. Next to each sample, there will be a list of elements. Next to each element, there will be a percentage - how much of that element was contained in the sample.

Radioactive-Dating

"WE'RE DATING ROCKS!!" Hahaha, going out with a rock isn't exciting. What we're doing in the lab is exciting! The idea is to use the Half-Life of the trace element Uranium to date the rocks. By comparing the amount of Pb (lead) to U (Uranium), we can date rocks back to millions of years ago. Carbon dating only goes back some thousands, I think. How to obtain the Uranium? Well, it turns out that the mineral Zircon has a pretty high Uranium content! (about 10 parts per million according to Wikipedia). So all we've got to do is find the grains of Zircon.

The process goes like this: we get some rocks, on average the size of a fist, and put them into a machine. The machine crushes rocks like the rocks are cheerios, so we have to make sure not to stick our hands into the machine. Afterward, we have to turn the crushed rock into a fine powder with another machine that relies on a spinning disk that grates against another that is identical and stationary. This is all very exciting and masculine, but in the end that is just a TENTH of the total work. The other 90% goes into cleaning and ensuring that no grains of Zircon from a previous sample-crushing goes into the next sample. With a fine powder from each sample, which is likely to contain about 30 particles of Zircon, we'll do some dry-sieving to remove some of the particles that are certainly not Zircon. Then it's a density filter: with a high density, but toxic (so I won't be allowed to participate in that part) fluid like Mercury, only Zircon + a few other heavy particles will fall; Others will float. Then it will be an filter based on weight and electrical charge. I'm not sure how it works, but it reminds me of Hall's Effect.

I think that's all for the first day of this blog.