Well, the end has arrived at last. Ok not quite yet, we still have 12 hours to go. But I won't be able to post anymore after this, so it's close enough. We will be arriving in the port of Suva, on the island of Viti Levu, in Fiji tomorrow (Sunday 3/8) at 8 am. I've been looking forward to this pretty much since I got on the boat, so needless to say I'm happy to be so close to done. Tomorrow night, we are going to have a party in town at the Bad Dog Cafe in Suva, which should be fun. After the party, we will all return to the boat for one more night on these crappy beds to avoid paying for a hotel. On Monday the 9th we will finish packing and get off the boat, and probably spend most of that day checking out Suva and the area around it. I've heard about a nice hike into a canyon nearby, and of course there's always the beach. On the evening of the 9th, we (the Hawaii crew) fly to Nadi on the other side of the island (yes, the island is big enough to fly across), which is about a 30 min flight or so. We will spend the night of the 9th in Nadi at the same hotel that we stayed in on the way in. The morning of the 10th we will take a boat out to Mana Island Resort, where we will stay until the 13th. This is the part of the trip that I have been looking forward to the most since the beginning, for obvious reasons. The resort owns the entire island and it is pretty much our playground for 4 days. Regan and I (and Michaela if we can convince her) are definitely going to be scuba diving, and I'm sure we'll do some snorkeling, swimming, island exploring, and relaxing as well. I plan on taking at least a few hundred pictures, so I'm excited for that as well. From there, we take a boat back to Nadi on the 13th, then fly out to Honolulu at 9:30 pm and arrive at 6 am (on the same day, which is a little weird). That's pretty much the plan for the next week, and I think it's safe to say it will be the best week of the trip.
I would say the only things I will miss about this experience are the people and the scientific discoveries. Most of the aspects of life on the boat I will definitely not miss, except maybe having all my meals cooked for me. Everybody that I spent time with on the boat was cool, and I enjoyed listening to various stories and getting to know them a bit. In terms of the scientific aspect, I'm glad I got the experience of seeing how the data is collected and learning a little bit about processing. Over the last few days, we have been going through essentially uncharted territory, so the element of new discovery is exciting. I enjoyed producing and looking at the mutlibeam bathymetry maps and sonar plots and trying to piece it all together. It's a bit like solving a mystery, and it's definitely one of the main reasons that I enjoy being a scientist. It's especially exciting when nobody out there has the answers yet, so any idea you come up with could be at least part of the explanation. There are some interesting features in the western part of the basin, including volcanoes of unknown origin with what appear to be relatively recent lava flows, faults, possible extinct spreading centers, and many other features on the seafloor that have yet to be explained. It's possible that my thesis work may be involved in trying to figure some of these mysteries out.
A few other random things:
1) We just crossed 180 longitude about 10 minutes ago, which (for sailor-types) is one of those milestones like crossing the equator or crossing 0,0, which is a particularly rare one. I am now a member of the Order of the Golden Dragon (they have a cheesy name like that for each one of these geographic milestones). Apparently, there is usually some sort of ceremony and certificates for these things, but for us it was pretty anticlamactic. From what I've heard the equator-crossing ritual sounds more like a fraternity hazing ritual, so maybe it's better that I avoided any ceremonies.
2) I have now eaten dinner three times and I'm wishing I had eaten it more often. Tonight, we had roast tenderloin (very similar to prime rib) and fried shrimp, with potatoes, rice, and a few other sides. Yesterday, we had grilled pork spareribs smothered with bbq sauce, corn on the cob, potatoes, and a few other sides as well. I'm completely blanking on what we had the night before, but it was something of a similar caliber. As much as I love eggs, bacon, and hashbrowns, you really can't compete with steak, shrimp, and ribs, especially when you have eggs, bacon, and hashbrowns every single day.
3) Sea life: Earlier today we officially crossed over the Lau Ridge and out of the Lau Basin, so we have been in significantly shallower water (<500-1000m as opposed to 2000-3000m). Also, we have been passing close to some islands in the eastern part of the Fijian group. Because of these factors (as well as not having the airguns on) there has been much more sea life sighted, unfortunately not by me, however. The MMO's saw some pilot whales from their tower and a bunch of people got to see dolphins while I was on watch duty. One of the OBS guys told me he was standing out on deck today and he saw a lot of flying fish and even a blue shark. I went outside at about 5:30 today to check it out and wait for the sunset and unfortunately I only saw 4 tiny flying fish desperately trying to avoid getting run over by the boat. I was amazed that even at 2-4 inches long they could "fly" for at least 50 feet before splashing back into the water. I guess I'll just have to wait until I see them up close and personal when I go diving in a few days. I think I can deal with that :)
4) Doubles Ping Pong Tournament: The semifinal round came down to 3 teams because of the odd number of people, so we did a round robin where each team played the other two. Every team ended up 1-1 in the round, so we had a sudden death playoff to determine who went to the finals. My team was randomly chosen to have a bye in the first round, so the other teams played to see who would face us in the finals. We played against Michaela and the Captain, who had beat us in the semifinals. In the final round, we came out victorious and were crowned the doubles champions. I wish I could take more credit, my teammate was the singles champ, but at least I held my own and didn't make us lose, so that's worth something.
Friday, March 6, 2009
Sunday, March 1, 2009
Update and Some More Science
We are officially six days away from dry land at last. Since the main experiment is done and we only need one student on duty at a time, we have switched our watch schedules so the 24 hrs is divided evenly between the 5 of us. My new watch is 9:40 am- 2:30 pm, which is much nicer, and allows me to transition to a relatively normal sleep schedule. I still have to be down in the lab working on data processing for a longer period of time, but I don't have to be around for 8 hours during the middle of the night anymore. All we have to do is check that the instruments are still running occasionally and make a log of our progress along the new survey lines every 30 min. There's not much else to report besides seeing a few squid while we were retrieving OBS's. Hopefully, we'll see some more sea life as we get closer to the much shallower Lau Ridge, which forms the western edge of the Lau Basin.
The new survey area is west of the seismic survey in a relatively unmapped and poorly understood portion of the basin. We are no longer using the airguns, and are just collecting bathymetry, sidescan sonar, gravity, and magnetic data. The methods for each of these is described below:
The airguns sole purpose is for collecting the seismic data: they produce a loud sound and a pressure wave which vibrates the seafloor (similar to an earthquake). These vibrations are picked up by the OBS's on the bottom of the seafloor and after lots of processing, give you an image of the surface of the seafloor and a few km below the seafloor.
We were collecting bathymetry, sidescan, gravity, and magnetic data while we were shooting the airguns as well, but we are now concentrating on an unmapped section west of the original survey area, and are going back and forth on E-W lines to cover the whole area.
The bathymetry data is collected with a multibeam echosounder, which shoots multiple beams of sound down toward the seafloor in an angular "swath," so we can collect data directly below the ship and off to the sides as well. Depending on the depth and the angle of the beams, the swath is usually around 5 miles wide. The beams reflect off of the seafloor and based on the travel time the instrument calculates the distance and comes up with a color-coded (based on depth) image of the surface of the seafloor (the bathymetry).
The sidescan sonar is similar in that it uses sound, but it's most accurate to the sides of the boat (hence "sidescan") and the data directly below is pretty much useless. I'm not sure why this is, but it has something to do with the reflection being to strong. The purpose of the sidescan data is to determine the type of materials that you are looking at. It doesn't give you a nice image of the seafloor like the multibeam, but you end up with a grayscale image based on the intensity of the reflection (aka backscatter). Harder materials like fresh volcanic rock show up as black on the image, and sediments are generally lighter colors. It's useful for determining areas of recent volcanic activity, identifying faults, and determining where sedimented areas are. While the topographic relief of faults is visible on the bathymetry, the sonar is much better for identifying them as faults rather than a ridge or something like that. This is because the majority of the faults around a backarc spreading center are "normal faults" where one block slips down at an angle relative to the underlying block. When this occurs, it exposes the harder rock under the sedimented surface, so the fault shows up as a nice linear black area (most of the time). This data will be very important for my thesis work, which involves identifying and interpreting the structures in the basin, as it is much better for seeing structures than any of the other data.
The magnetometer measures the magnetization of the seafloor. When new basaltic crust (high iron content) is formed, the iron grains are aligned in the direction of the earth's magnetic field at that time and "frozen" in place when the lava hardens. Since the earth's magnetic field changes over time and even flips polarization completely (i.e. the north pole becomes the south pole), crust formed at different times will have iron grains with orientations corresponding to when it was formed. The magnetometer measured these orientations and can give an idea of the relative age of the crust. If the crust was actually formed at a spreading center, you will see "stripes" parallel to the spreading center corresponding to times of different polarization of the earth's magnetic field. If it was formed another way (i.e. arc volcanism) you will see a less organized pattern. The data we are collecting now can potentially resolve a contentious question of how the crust on the west side of the basin was formed, which is pretty cool. This data alone could provide enough information for a thesis to be written. It will likely be the other student under my advisor who will use this, not me.
The gravimeter measures the varying gravitational field of the seafloor. This is mostly controlled by the density of the material (higher density = more mass = stronger gravity). Gravity data is the least intuitive of all of these types, because it doesn't necessarily correspond to anything you can see on the seafloor (i.e. higher topographic relief does not necessarily mean higher gravity). One use of gravity data that I know of is to differentiate between types of volcanoes. Volcanoes formed along a spreading center are composed mostly of basalt, which is a very dense volcanic rock. Volcanoes formed along the volcanic arc due to subduction have a higher proportion of andesite, which is a less dense volcanic rock. Therefore, with gravity data, you can actually determine with reasonable accuracy whether a given volcano on the seafloor is formed at a spreading center or a volcanic arc without having to take any rock samples from it. There actually are a number of volcanoes in the area we are covering whose origins are unknown, and the gravity data should provide some valuable insight on that.
The new survey area is west of the seismic survey in a relatively unmapped and poorly understood portion of the basin. We are no longer using the airguns, and are just collecting bathymetry, sidescan sonar, gravity, and magnetic data. The methods for each of these is described below:
The airguns sole purpose is for collecting the seismic data: they produce a loud sound and a pressure wave which vibrates the seafloor (similar to an earthquake). These vibrations are picked up by the OBS's on the bottom of the seafloor and after lots of processing, give you an image of the surface of the seafloor and a few km below the seafloor.
We were collecting bathymetry, sidescan, gravity, and magnetic data while we were shooting the airguns as well, but we are now concentrating on an unmapped section west of the original survey area, and are going back and forth on E-W lines to cover the whole area.
The bathymetry data is collected with a multibeam echosounder, which shoots multiple beams of sound down toward the seafloor in an angular "swath," so we can collect data directly below the ship and off to the sides as well. Depending on the depth and the angle of the beams, the swath is usually around 5 miles wide. The beams reflect off of the seafloor and based on the travel time the instrument calculates the distance and comes up with a color-coded (based on depth) image of the surface of the seafloor (the bathymetry).
The sidescan sonar is similar in that it uses sound, but it's most accurate to the sides of the boat (hence "sidescan") and the data directly below is pretty much useless. I'm not sure why this is, but it has something to do with the reflection being to strong. The purpose of the sidescan data is to determine the type of materials that you are looking at. It doesn't give you a nice image of the seafloor like the multibeam, but you end up with a grayscale image based on the intensity of the reflection (aka backscatter). Harder materials like fresh volcanic rock show up as black on the image, and sediments are generally lighter colors. It's useful for determining areas of recent volcanic activity, identifying faults, and determining where sedimented areas are. While the topographic relief of faults is visible on the bathymetry, the sonar is much better for identifying them as faults rather than a ridge or something like that. This is because the majority of the faults around a backarc spreading center are "normal faults" where one block slips down at an angle relative to the underlying block. When this occurs, it exposes the harder rock under the sedimented surface, so the fault shows up as a nice linear black area (most of the time). This data will be very important for my thesis work, which involves identifying and interpreting the structures in the basin, as it is much better for seeing structures than any of the other data.
The magnetometer measures the magnetization of the seafloor. When new basaltic crust (high iron content) is formed, the iron grains are aligned in the direction of the earth's magnetic field at that time and "frozen" in place when the lava hardens. Since the earth's magnetic field changes over time and even flips polarization completely (i.e. the north pole becomes the south pole), crust formed at different times will have iron grains with orientations corresponding to when it was formed. The magnetometer measured these orientations and can give an idea of the relative age of the crust. If the crust was actually formed at a spreading center, you will see "stripes" parallel to the spreading center corresponding to times of different polarization of the earth's magnetic field. If it was formed another way (i.e. arc volcanism) you will see a less organized pattern. The data we are collecting now can potentially resolve a contentious question of how the crust on the west side of the basin was formed, which is pretty cool. This data alone could provide enough information for a thesis to be written. It will likely be the other student under my advisor who will use this, not me.
The gravimeter measures the varying gravitational field of the seafloor. This is mostly controlled by the density of the material (higher density = more mass = stronger gravity). Gravity data is the least intuitive of all of these types, because it doesn't necessarily correspond to anything you can see on the seafloor (i.e. higher topographic relief does not necessarily mean higher gravity). One use of gravity data that I know of is to differentiate between types of volcanoes. Volcanoes formed along a spreading center are composed mostly of basalt, which is a very dense volcanic rock. Volcanoes formed along the volcanic arc due to subduction have a higher proportion of andesite, which is a less dense volcanic rock. Therefore, with gravity data, you can actually determine with reasonable accuracy whether a given volcano on the seafloor is formed at a spreading center or a volcanic arc without having to take any rock samples from it. There actually are a number of volcanoes in the area we are covering whose origins are unknown, and the gravity data should provide some valuable insight on that.
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