7 weeks 5 days
Core on the floor...
Submitted by James Bendle on Sun, 01/24/2010 - 00:40
The picture above shows Stephanie Carr (the microbiolgist and other organic geochemist onboard) and me looking happy with the cores coming up from our current (the 2nd) core site.
We weren't as happy with the first drill site, although it threw up some surprises and made for an interesting story! So let's go back to last Thursday, the captain made the annoucement that the first core was imminent and the scientists crowded onto the core deck to see the first core come in (see the picture from Rob Dunbar below).
My colleagues Stephanie Carr and Travis Hayden have posted really great stories about what happened next, including explaining the amazing drilling technology that allows ship like the Joides Resolution to drill hundreds of meters into mud and rocks in the ocean floor that is more than 3000m below us. The very short version of what happened is that 1) we were expecting to core into soft mud, 2) we hit hard sand and gravel, 3) we broke some coring equipment in the process (don't worry, it happens sometimes and there are plenty of spares on board!) , 4) we packed up and sailed the current site (which has turned out to be much better).
So why did we want (and expect) to find mud and why were we suprised (and some of us disappointed) to hit sand and gravels?
The most useful sediments for studying past climate change over long time-scales (thousand to millions of years) are those that have collected continuously over time. These sediments contain fossils and chemicals which record information on climate at the time the sediments were desposited. The fossils include tiny plankton and algae which lived in the sunlight upper layers of the ocean. When they die the tiny remains sink into the deep ocean and collect in the layers of accuring sediment.
Using various methods scientists can read the story of climate change recorded by the fossils and chemicals. We love the sediments from the quiet depths of the deep ocean because each layer is like a page of book (... the "book of climate change"), the story has been written page by page over millions of years. The fossils and chemicals that we measure are like the letters and words written down in the book. You can see from the picture above that the earth's surface is not quiet! Sediments and rocks are continuously being disturbed, eroded, deposited, deformed, re-eroded, shaken by earthquates, transported by rivers, blown around by dust storms etc. Near to the edge of the continents the land tips steeply down into the ocean depths - this is the continental shelf. The continental shelf is an area where large amounts of sediment can be distrubed by waves, storms earthquakes and periodically flow, slide or tumble down into the deep ocean.
When this happens it's like someone pulling out the pages of our book of climate change and jumbling them all up, it can spoil the story! Our coring site was in the abyssal plain, the deepest, quietest part of the ocean, we expected undisturbed muddy sediments, but instead we hit hard sand and gravel. These had been transported far out into the deep ocean, maybe in a debris flow similar to the one one in the figure above. Were weren't expecting such flows to have reached so far away from the continental shelf. So sometimes its hard to find the quiet parts of the deep ocean, where the pages of our book remain undisturbed!
After breaking some equipment and nearly getting our drill stuck in the sands and gravels, we pulled up and moved to our new site, where the ocean floor is very deep (nearly 4000m) ....and, as described by Travis and lambchop, it is going well, so far. We have drilling down through hundreds of meters of undisturbed sediments which were deposited during the the last 20 million years (during a period called the Miocene, when our biological ancestors were evolving into apes that were similar to modern chimpanzees). Our Miocene sediments contain countless billions of beautiful, tiny fossils of diatoms that lived during the Miocene and also some layers of pebbles and stones which were dropped into the layers of sediments by melting Miocene ice-bergs.
PS – More official photos have been posted here. The next video report is coming soon, including the return of penguin TV and more information on the most unusual scientist on this expedition (despite some tough competition)…!
- What’s the food like?: Only real highlight of the last few days was salami pizza...the food of the gods.
- What’s on lab stereo/ipod ?: Tribe Called Quest (and some old school hip hop), The Kinks, The Who, Amiee Mann.
- What’s the weather like?: Good, calm and clear, about 3 *C.