To record these lower-crustal and upper-mantle phases as “first arrivals”, where they are not obscured by the arrival of energy from shallow paths, we use long lines. Long lines mean lots of receivers and lots of driving to deploy and recover these instruments. We could have used lots of sources instead, but the blasts we used to get seismic energy into the lower crust and upper mantle in this experiment take a lot of time and money to setup. Receivers are much cheaper, so we used a lot of them. (For similar wide-angle/long-offset work at sea, airgun sources are cheaper than putting seismometers on the seafloor, so we use many shots and a smaller number of receivers out there.)
This time-lapse video shows Team 13 of 14 recovering 89 of the 1200 total short-period seismograph stations from where our line crossed Fort Benning, near the northwestern end of the line.
Nathan Miller, LDEO
Weather map during deployment. When the time came to install our 1200 small seismographs across Georgia at the flagged positions, the rains came…. A lot of rain. During our first deployment day, we received 1-2 inches of rain, and another wave of rain clouds came through on Day 2 (check out map). Roads that used to be easily passable became mudholes or were flooded with water. All-wheel-drive vehicles and drill rigs alike got stuck, and a few station locations could only be reached on foot. Our hard-working field crew labored in the rain digging holes and deploying seismometers. Vehicles, equipment and people were covered in the famous Georgia red clay (and other muds and sands of Georgia and northernmost Florida). Adding insult to injury, problems with the programming of some of the instruments meant that we actually had to pick up and redeploy many of them. It was a mudbath. Nonetheless, our field crew managed to deploy 1200 seismometers across Georgia by Tuesday at sundown. It was an impressive show of endurance, and an inspiring display of positivity given the number of people that were still smiling and upbeat at the end of it all. A couple of days later, after our seismic shots, it was already time to pick up the instruments, and the weather changed completely. The sun shined on SW Georgia, and we picked up almost every last seismometer in just one day under blue skies…. Donna Shillington, LDEO
To someone who hasn't seen a seismic source shot before, there really isn't a good way to describe what a good shot feels like, except as something you haven't felt before. We had a number of students watching L1-05 being shot, since this location is quite close to Americus. The video of L1-05 is completely lacking in drama, which is a good thing; but that shot gave us all a great ride. The 100 pounders 06 and 07 were also surprisingly good.
We made gathers for most of the shots today. The dataset is fantastic, and 05, 06 and 07 produced super record sections. L1-08 committed most if its energy to the air, but it shook the ground nicely and I've got a feeling those data are going to be great too.
The video is here: http://youtu.be/DNINWj2kf1s
Gliders and buoys and robots — oh my!
Over and through the ocean they fly.
Oodles of data from sensors galore,
Studied by many, far from the sea’s roar.
A real revolution, there seems little doubt,
But what of the crew who never sail out?
To peer in the great briny main without drinking …
How might that impact the next wave of thinking?
A Sea Change for U.S. Oceanography, Science 2013
The New Generation of Sea Scientist, Science 2013
This is one in a series of poems based on science news, written by Katherine Allen, a researcher in geochemistry and paleoclimate at the Lamont-Doherty Earth Observatory. First posted 3/1/13 on Allen’s website.
South-central part of the seismic line. The yellow line is team 5's section. We have been in a relatively rural part of Georgia and as a result have not encountered many locals save a few who have stopped to ask if we are ok. However, we have seen quite a few interesting things that are quite out of the ordinary (to me at least).
Friendly Muscovy duck.Rocks in a stream bed with associated pink spongy material (?)
Spanish moss.Linguoid (current) ripples on a washed out road. We have also seen quite a few old abandoned farm houses in various stages of aging...
At least 10-15 dogs were standing guard at this house, including about 8 puppies.
Caroline making some new friends.
All said we have dug 122 holes in team 5's stretch. We have also helped deploy instruments in other sections as well and while doing so have seen others hard at work.
Meghan and Nate getting it done!Along the way the cars have taken quite a beating and have actually held up pretty well. Although there have been a few instances where people got stuck, I think that the people with the toughest job will be the guys that have to detail the cars upon their return...
A more appropriate vehicle (?)And lastly here's a couple more random pictures that I thought were interesting.
The large disparity in fuel grade gas prices.
A ~perfectly leveled geophone (it's harder than you'd think).Hopefully this random selection of pictures was entertaining. Up next we will post about last night's "shots." In the meantime, I can say that they were all successful with varying degrees of excitement. The most important thing is that all of our hard work is being realized as the instruments are recording refractions from buried geology that will help us unravel some of the mystery that surrounds events that happened in this area long ago.
James Gibson, LDEO
Chastity AikenGeorgia Institute of Technology
into the field where they undoubtedly got a little mud on their tires. Each pair of field assistants was given a segment of the seismic line to drive and flag locations for instrument installation deemed safe both from the seismograph (i.e. dry, firm soil) and the install team (i.e. a safe distance from the road). Given the shear distance of the seismic line, teams found themselves amid diverse backdrops from rolling farmland with overly friendly cows to buzzing residential neighborhoods to sandy stretches flanked by towering groves of Ponderosa Pine trees. Antonio placing a flag and using a GPS device to note the location where a
seismograph will be installed amid the sandy surroundings of a Ponderosa Pine farm.Every team was able to flag all their sites within just two days leaving us the luxury of a sunny Saturday morning free for exploring more of our beautiful Georgia surroundings. Next up is the actual task of installing the 1200 seismographs which will involve twice the people, six more (temporarily clean) vehicles, and of course countless exciting adventures from the field. Happy (almost) St. Patrick’s Day from Americus!A picturesque county road near Jasper, FL along which instruments will be deployed.-- Natalie Accardo, LDEO
Adrian Gutierrez, 13 March 14
7:30 am: Leave Georgia Southwestern State University, where we are staying, and head to the site8:20 am: Arrive at site 8:30 am: Start drilling and take geological samples every 5 ft.
9:00 am: Dyno Nobel truck arrives; load emulsion into cut PVC pipe sections that serve as a holders for emulsion. 9:30 am: Surprise visit from other scientists on the project9.50 am: Setting up the booster in the emulsion.11.20 am: Loading the explosives into the drill hole12.00 pm: Drill crew starts removing their equipment12.45 pm: Tagging the charges and plugging the hole3.15 pm: Move onto the next drill site.Nighttime: Finally back to the dorm.
An ancient grain of zircon found
In Jack Hill sandstone north of Perth,
Inside its crystal lattice bound:
Secrets of our planet’s birth.
The oldest grain (we rock hounds swoon),
Tells of magma oceans past,
An early impact yields the moon;
And all of this occurred so fast!
The zircon’s old, which then implies
That solid rocks must be still older.
In Canada, a sequence lies,
With implications even bolder!
A pattern locked within old lava
Echoes patterns from the deep;
Mariana-like subduction …
To plate tectonics, take the leap!
Hadean times are cloaked in intrigue,
Eons distant, full of strife,
Yet it seems these rocks held promise,
Full of boron, primed for life!
In the news:
New Record for Oldest Earth Rock, Sky and Telescope
Hadean age for a post-magma-ocean zircon confirmed by atom-probe tomography, Nature Geoscience
The Dawn of Plate Tectonics, Science Now