GEOFORM 2009

From October 2nd-13th, 2009, a science team led by Scripps Institution of Oceanography at UC San Diego graduate student Jared Kluesner is conducting research aboard Scripps research vessel New Horizon to explore the depths of the Gulf of California. The team will study the geological process at work in this region where the seafloor is slowly rifting apart and new ocean crust is emerging through volcanoes and other underwater features to form a new ocean basin in the Pacific.

Follow along as the GEOFORM (Geological Exploration of the Formation of a Rifted Margin) research team explores the Gulf of California and recounts its observations through daily blogs and photos as they encounter deep-sea life and unique geological features, such as underwater volcanoes, while conducting research at sea.
      GEOFORM2009 is supported by UC Ship Funds

Ship Tracker
Get daily updates with images & location information from Chief Scientist Jared Kluesner and his team as the ship makes its month-long journey through the Pacific and into the Gulf of California!
Scientists Profiles
Read about each member of the crew and how they will contribute to the research that will be conducted during the GEOFORM 2009 cruise.


Follow along with the cruise by reading the blog (by Scripps graduate student Sandy Kirtland, see below) and posting questions in the comments section after each entry.


20Nov/092

Press Releases

Click on the links below to check out some recent articles about the cruise!

SIO Explorations electronic magazine: "Dredging up the Truth"

UCSD weekly magazine TW@UCSD

Indiana State University article about Ashley Burkett/GEOFORM cruise


Click here to read this post's comments! Click here to contribute to this post's comments!
Filed under: Uncategorized 2 Comments
17Oct/090

GEOFORM on Google Earth!!

Make sure to check out the GEOFORM cruise on Google Earth. Under the Layers tab click the drop down menu for "Ocean" and select "Ocean Expeditions". Just zoom in on San Diego and click the "Scripps Nimitz Marine Facility (MARFAC)" icon (looks like a sailing ship logo). A special thanks to Annie Reisewitz for making this possible!


Click here to read this post's comments! Click here to contribute to this post's comments!
Filed under: Uncategorized No Comments
13Oct/0912

Last day aboard

The weather didn't cooperate for our last day in the Gulf. The captain had been watching a low pressure system forming further south in the Pacific, and on Sunday afternoon we started to see clouds on the horizon. We pulled up the dredge in the rain; combined with the mud, it was quite a mess! During the evening the swell began to pick up, and we had a bumpy transit southeast towards Mazatlan. Despite lots of success throughout the cruise, we unfortunately lost the dredge at our last target! We're not sure exactly how it happened--there was no unusual pull on the wire. After that, our dredging was finished, and we continued on to port. On the R/V New Horizon, you can really feel the swell and the waves hitting the ship. It was impossible to walk around without running into things. We docked last night and slept onboard, but the captain woke us up early to disembark, since the swell was too big and was pushing the ship against the dock. Early this morning, we packed up our things, said our goodbyes, and left the ship.

I hope everyone has enjoyed following along with our cruise! Please feel free to continue asking questions. We'll check the website regularly to respond to any comments.


Click here to read this post's comments! Click here to contribute to this post's comments!
Filed under: Uncategorized 12 Comments
11Oct/092

Tectonics and sills

 

The sun sets over the Baja Peninsula.

The sun sets over the Baja Peninsula.

I thought I'd use this post to wrap up a few topics I began in earlier entries. In "Last dredge in the Pacific," I started to discuss the tectonic history of the Gulf, leaving off around 12 million years ago when subduction of the Magdalena microplate stopped and Baja transferred to the Pacific Plate. With the Pacific Plate moving to the northwest and the North American plate moving west, tension caused rifting to begin. The arc volcanoes in this area (Baja and present-day Mexico) meant that the crust was heated and weak and easier to break apart. This situation continues at present, so the Gulf is an oblique rift zone, meaning a combination of rifting with transform motion. The present-day Gulf contains multiple spreading centers linked by separate parallel transform faults that form a stair-step pattern up its length. At its southern end is the East Pacific Rise and at its northern end is the San Andreas fault system. The San Andreas is a transform fault that runs east of San Diego and is responsible for a number of large earthquakes. That means that San Diego is actually on the Pacific plate, not the North American plate. The motion of the Pacific plate relative to North America and the consequent opening of the Gulf means that San Diego will one day be part of a Baja island out in the Pacific!

I also said I'd discuss a bit more about sills. With so much sediment pouring into the Gulf from the nearby continental landmasses, all the magma rising to the surface can't make it to the seafloor. As a result, magma injects vertically into the sediments as dikes and spreads horizontally to form sills. The magma spreads horizontally at a level of neutral buoyancy; that means the pressure from below matches the weight of the overlying sediments. Going back to our marshmallow analogy from the pillow lavas, imagine that graham crackers are sediment layers. The squeezed, melted marshmallow between the crackers would be the sill.

Sills are important in the Gulf for a number of reasons. For one thing, they can complicate identification of the boundary between continental and oceanic crust, since these sills can form off of the main spreading axis and jumble magnetic signals. Sills also "feed" fluid flow systems, like hydrothermal vents, and can generate hydrocarbons. When sills form they superheat the surrounding sediment. Hot things rise, so superheated pore waters, dissolving all sorts of chemicals from the sediment, will issue from the seafloor above sills. When sediments are rich in organic matter (decayed plant or animal matter), sills can produce thermogenic methane and other hydrocarbons.

When superheated waters (greater than 400 degrees Celsius or 750 degrees Fahrenheit ) reach the cool ocean waters (around 2 degrees Celsius or just over freezing) dissolved chemicals can precipitate out, forming hydrothermal deposits. These include some of the familiar pipes and chimneys commonly visible in pictures of hydrothermal vents. It would be hard to image something so small using our sonar systems (like CHIRP), but side-scan sonar attached to deep tow vehicles can detect these deposits as reflective patches on the seafloor. Side-scan sonar emits pulses of sound over a large swath of the seafloor as the tow vehicle travels over the surface. Peter was the first person to discover hydrothermal vents in the Gulf of California. He found these in Guaymas Basin, which is further north in the Gulf than we're traveling on this cruise, but there are hydrothermal vents in other parts of the Gulf too.

One neat thing about studying Gulf geology is that it gives us a window into the past formation of other ocean basins. Plate tectonics has radically changed the appearance of the Earth over time. For instance, the Atlantic Ocean, currently the second largest ocean in the world, was once very similar to the modern day Gulf. The Atlantic Ocean didn't exist prior to 130 million years ago. It started to form as the most recent supercontinent (called Pangaea) broke apart. The early Atlantic also must have had huge amounts of sediment pouring into it and multiple sills injecting into the crust. The rifting of continental crust and the formation of an ocean occurring today in the Gulf are thus a young parallel to the Atlantic's past!

 


Click here to read this post's comments! Click here to contribute to this post's comments!
Filed under: Uncategorized 2 Comments
11Oct/096

Reflections on some discoveries at sea

Cast of bivalve on dredge rock.

Cast of bivalve on dredge rock.

The dredging continues, and we had perfect weather yet again yesterday. In the morning Jose, a graduate student at UNAM, told me that he'd dropped a stone off the edge of the ship and had been able to watch it sink through the water for 20 seconds. He brought out another stone to demonstrate: the sea surface was still, and I was amazed by the brilliant blue. You could calculate the speed of the stone falling through the water by balancing the forces acting on it, which would be gravity balanced by the resistive force (or drag) of the water. This resistive force would be a factor of the size of the stone and the density of the water and be proportional to its speed. If you timed the rock as it sank, you could use this speed to solve for the depth of the rock when it disappears.

One way oceanographers have long measured the transparency of water is through something called a Secchi disk. This disk is generally about a foot in diameter with alternating quadrants of black and white. You attach the disk to a line and slowly lower it into the water while someone watches to record the point where the disk is no longer visible. This depth is called the Secchi depth and is a common measure of water clarity.

I mentioned the color of the water today, but have you ever wondered why the oceans are blue? When light hits the water, some of it reflects and some of it absorbs. Blue wavelengths are short compared to the other colors in the visual light range of the electromagnetic spectrum. While other colors are absorbed higher up in the water column, blue light can penetrate to greater depths, and the reflection of these short blue wavelengths is what your eye detects. Particles in the water (from biology and/or turbidity) can alter the absorption of light and change the color.

Possible sea lion gizzard stone.

Possible sea lion gizzard stone.

Anyway, we had a number of successful dredges under these fine conditions. Among all the rocks we dredged up today, I had two favorites. The first had a fossil cast of a bivalve (a double shelled animal like a clam). A cast is a type of fossil formed when a mold (or imprint) of an organism fills in with minerals. The shape of this fossil means that there must be another rock with an external mold of the same bivalve. Peter found my second favorite rock. This rock is very smooth and round. The usual explanation for smooth rocks with rounded edges is that they have traveled long distances, but this rock was so round that Peter guessed it might be a sea lion gizzard stone. Sea lions, like chickens and other birds, swallow stones to help grind up the food in their stomachs. All that grinding can produce very rounded stones, like this one.

 

 

 


Click here to read this post's comments! Click here to contribute to this post's comments!
Filed under: Uncategorized 6 Comments
10Oct/090

CHIRP

Turn up the volume on your computer and play the video below to hear what a CHIRP sonar sounds like! Click here to view some animations that explain how sonar is used in marine science.

http://www.geoform2009.com/images/uploads/CHIRP.m4v


Click here to read this post's comments! Click here to contribute to this post's comments!
Filed under: Uncategorized No Comments
9Oct/091

An idyllic day in the Gulf

Today the sea couldn't have been much calmer and the sky was free of clouds--perfect conditions for a few extramural research cruise activities. I spent the day working the A-frame out on the fantail. This job consists of pushing a lever back and forth between the "in" and "out" positions in order to guide the dredge as it lowers into the water and then returns to the deck. We dredged four targets in the Carmen Basin, bringing up rocks on all but one. Even after 17 dredges, it's still interesting to guess, as the dredge breaks the surface, what's going to be inside. Our last dredge of the day was full of particularly muddy rocks, which meant sifting through gobs of greenish-brown mud to separate the rocks from the sediment. This is definitely a dirty (and smelly) job. I had the additional task of hosing down the fantail after we'd created a big, muddy mess.

Large animal found swimming around the stern.

Large animal found swimming around the stern.

While pulling up the dredge in the afternoon, everyone got particularly excited upon sighting a large, eel-like animal a few feet below the surface. I first noticed it off the starboard side, seeing something metallic and more than 10 feet long flashing in the water. Whatever it was, it seemed curious about the ship, hanging out just off the stern for probably around 10 minutes. Unfortunately, no one could identify it--despite a few calls of "sea monster!" Where are all the biologists when you need them? If anyone has any suggestions based on this photo, we'd love to hear them.

In the evening as the sun began to set over the mountainous Baja Peninsula, Doris Pinero, who recently completed her Master's thesis at CICSE studying the geology of the Gulf, gave us a description of her research on a few islands west of Carmen Basin. In addition to interpreting seismic profiles from the Farallon Basin, Doris obtained the first geological samples of plutonic rocks from these islands, which include Isla Santa Cruz, Isla San Diego, and Isla Santa Catalina. She collected the samples by hand, sailing to the islands from the city of Loreto on the Baja Peninsula. It wasn't easy for them to land a boat on the islands; instead, someone had to jump from the boat to the rocks!

 

Doris Pinero gives a talk about the nearby islands that she sampled last year.

Doris Pinero gives a talk about the nearby islands that she sampled last year.

To round off a perfect day, Kent (our navigational officer), took us out onto the bow for stargazing and a lesson on celestial navigation. The moon had yet to rise, so the sky was phenomenal. Kent had a super-powerful green laser to point out constellations; it was strong enough that you could see the laser beam shooting up into the sky. He pointed out the North star, explaining how sailors have used it to navigate for centuries. Depending on your latitude, the North star will be at a different angle from the horizon. At the North Pole, it would be directly overhead, while it would sit just above the horizon if we were at the Equator. Kent pointed out a number of different constellations--like Sagittarius, shaped like a teapot, with the Milky Way coming out of its spout as steam. He also told the story of Cassiopeia, the jealous mother of Andromeda, who sent the monster Scorpius into the sky to chase after Andromeda's love Orion, whom Andromeda hid in the heavens as protection from her mother. I sat staring up at the sky for awhile, awed, and even noticed a few shooting stars!

We reached the northernmost point of our cruise today, so from now on we should be transiting south, with more dredge targets along the way. Now off to bed!

 


Click here to read this post's comments! Click here to contribute to this post's comments!
Filed under: Uncategorized 1 Comment
9Oct/092

All about rocks!

Given all the rocks we're collecting on this cruise, I thought it was high time I wrote a bit about rock types. I think I mentioned earlier that the few previous samples from this region were all different, but what does that mean? Perhaps you've never really thought about it before, but first of all, what actually defines a rock?

Rocks are groupings of various minerals, and minerals are various elements combined in a crystalline structure. Overall, the chemical composition of rocks is generally quite complex. The dominant element in all rocks is silica, since this is the most abundant element in the Earth's crust. One of the first things you'll learn in any geology class is the rock cycle. This refers to all the processes that a rock undergoes, starting with the formation of basaltic magma and ending with the melting of subducted rocks. Along the way, we can divide rocks into three primary types: igneous, sedimentary, and metamorphic.

Igneous rocks are formed from the solidification of magma, and there are two primary types. The first type is extrusive igneous rocks (also called volcanic rocks) formed when magma comes up to the surface (as in a volcanic eruption). I've referred frequently to basalts, which are common extrusive igneous rocks making up the new crust formed at mid-ocean ridges. The other type of igneous rocks is intrusive (or plutonic). These rocks form when magmas crystallize at depth in the Earth's crust--a common example of a plutonic rock is a granite. The quick way to tell apart extrusive from intrusive rocks is to look at the crystal size of the minerals in the rock. If you can't distinguish individual crystals, the rock is probably volcanic. If individual crystals are big, it's probably plutonic.

When rocks are weathered and altered by erosional processes, including the involvement of organisms, the result is sediment. Sediments can come in a range of sizes--from clays up to larger fragments of rocks, or clasts. When these sediments become compacted or "glued" together, they form sedimentary rocks.

Finally, when rocks are subjected to changing environmental conditions, especially in temperature and pressure, they are metamorphosed. These conditions can actually change the mineralogical composition of rocks. Metamorphic rocks are rocks that have undergone such recrystallization, and are frequently identified by the degree of alteration they have experienced.

After this initial breakdown, things get a lot more complicated! To identify different rocks within each broad category, you need to be able to identify minerals as well. Luckily, we have petrologists onboard (scientists who study the processes that form rocks), and they are much better than I am at identifying differences between the samples we collect. Of course, the first step to identifying rocks is to have a keen eye. Try picking up any rock outside--what color is it? can you see individual particles? how big are they? is the rock the same throughout, or are there bands of different colors and/or textures?

Each time the dredge comes up, we go through this type of process to separate different rocks and choose which ones to saw in half and describe in more detail. Depending on the type of environment we're sampling, we can find many different types of rocks. Along a spreading center, we're likely to find volcanic rocks, whereas we might find metamorphic rocks associated with a subduction zone. When we can combine sonar and bathymetric data with rock samples, we can give a confident interpretation of the tectonic environment.


Click here to read this post's comments! Click here to contribute to this post's comments!
Filed under: Uncategorized 2 Comments
8Oct/096

On to Farallon Basin

With all this dredging, I'm becoming familiar with the deep rumbling of the bow thruster and the sudden jerks of the ship when there are big pulls on the wire. After all, we are currently transiting to our 13th dredge target. There are just four full days of dredging left, but at this rate we should be able to get a lot more done.

Conditions have varied somewhat since we entered the Gulf, but last night the sea looked as calm as a lake, with the moonlight reflecting off the water. Only slightly marring the weather were visits by numerous seabirds, who must see the New Horizon as an ideal place to rest. This proclivity is unfortunate for the crew, whom I overheard musing about the benefits of working on deck in ponchos.

3D image of Farallon spreading center

3D image of Farallon spreading center

Today we entered the Farallon Basin (check ship track for exact location) in the southwestern Gulf. The Farallon Basin has a spreading axis at its center, so the seafloor here is oceanic crust, transitioning into thin, rifted continental crust at the basin's edges. Spreading centers in the Gulf, like this one in Farallon, are different from more well known spreading axes like the Mid-Atlantic Ridge (MAR) and East Pacific Rise (EPR), since they form as deep rift valleys rather than bathymetric highs. Some of these rift valleys are over 3,000 meters deep! One difference is that the Gulf spreading centers are so close to land. Unlike the MAR or EPR, these spreading centers are inundated by massive amounts of sediment that pour into the Gulf. One familiar source of terrigenous input to the Gulf is the Colorado River, which empties into the northern Gulf (though no longer consistently, as a result of overuse for irrigation). Further south, especially in the eastern Gulf, the Mexican Sierra Madre Occidental mountains are a more important source of sediment.

The second major source of sediment is pelagic rain from highly productive surface waters. This "rain" is actually organic debris from biota. High surface water productivity is a result of strong wind-driven upwelling, which causes phytoplankton blooms. Diatoms, or microscopic algae, are one of the major components of these blooms. They are also one of the most important photosynthesizers in the ocean. When conditions are right, diatoms can reproduce extremely quickly. Upwelling provides these conditions by replenishing nutrient-depleted, warm surface waters with deeper waters that are filled with important nutrients like nitrate and phosphate from the decomposition of organic matter. Diatoms form a test (or outer shell) made of silica, so sediments in the Gulf are silica-rich.

All this sediment is important because it influences the way new ocean crust forms. Out on the MAR or EPR, underwater eruptions bring basalts into contact with cold water, causing the formation of pillow lavas. These distinctive shapes form as the outer surface of the lava cools and hardens into a roundish pillow shape, at which point hotter lava breaks through and builds another pillow on top. My advisor, Dick Norris, has a fantastic visual aid for demonstrating pillow lavas, which I highly recommend should you have an extra bag of marshmallows handy while camping. After squishing up the marshmallows into one mass (handily achieved by sitting on the bag), simply throw the gooey ball onto a campfire. Next, watch as the top of the marshmallow ball burns; then, flows of heated marshmallow break the surface and begin to form pillows. Anyway, those layers of sediment on the Gulf seafloor prevent the formation of pillow lavas. Magma can't extrude onto the seafloor surface; rather, it injects vertically into the sediments as dikes, then spreads out horizontally as sills. I'll get into sills more later, since this is a favorite topic of Jared's.

Rock sorting table in the lab

Rock sorting table in the lab

Our most recent dredge was over a seamount in the Farallon basin that looked curiously like a sombrero. Our next target will be another seamount, 1,900 meters deep and surrounded by a moat-like ring. Our rock collection is growing rapidly!


Click here to read this post's comments! Click here to contribute to this post's comments!
Filed under: Uncategorized 6 Comments
8Oct/090

Dredging at night

We continue to dredge around the clock, so I thought I'd post a few videos of dredging shot out on the fantail. The first video shows us flipping the dredge to get out all the rocks stuck at the bottom. The second video shows the dredge breaking the sea surface. Enjoy! I'll write more soon!

http://www.geoform2009.com/images/uploads/VID00026-iPhone.m4v http://www.geoform2009.com/images/uploads/VID00031-iPhone.m4v


Click here to read this post's comments! Click here to contribute to this post's comments!
Filed under: Uncategorized No Comments

Pages

Categories

Archives

Admin