Drilling deeper than ever before : Expedition 312 and 309

ocean crust diagram

Each time a party of scientists head out to sea on the JOIDES Resolution they give that trip a new number to help identify the discoveries they find. Right now the scientists are out on Expedition 312 to study the deepest layers of ocean crust by drilling deeper than ever before. They will do this by going back to a hole they already drilled on Expedition 309 and starting at the bottom and going even deeper.

What are they looking for?

Expeditions 309 and 312 will provide us with a complete look at the base of the ocean's crust going through several types of rock: volcanic basement rocks, sheeted dikes, and the uppermost gabbro. By drilling through all of these layers we will get a more complete picture of what the bottom of the earth's ocean crust looks like. As a matter of fact, if we drilled through any more rock types we would hit the mantle!

Where are they going

map of location

All over the planet there are ridges where new ocean crust is being created by magma welling up from inside the earth. In the Pacific Ocean there is a spreading ridge called the Southern East Pacific Rise where new ocean crust is being created at a geologically fast pace (more than 200 millimeters per year). Expeditions 309 and 312 are drilling into the crust that was created by this fast spreading ridge about 15 million years ago. The ocean crust is thin here and will allow the scientists to see a wider array of rock types in the crust.

Why is this so important?

Geology is a science born out of people looking very closely at the rocks they saw around them. However, since we can't directly observe what the earth looks like thousands of feet below the ground we have had to make educated guesses.

Scientists do this in many ways. They can study waves as they pass through the earth with very sensitive seismic sensors, in a processes called seismology. This is the same study that helps us pinpoint earthquakes around the world. They can also observe and do experiment on rocks that used to be deep inside the earth millions of years ago and are no thrust up onto the surface.

But, by drilling down into the earth's crust deeper than ever before though scientist are able to directly look at the rocks that make up our planet below the surface. In many cases we are even finding out that our ideas about what it looks like down there are far to simple.

Texas A&M scientist Jay Miller sums it up perfectly. "Each time we drill a hole, we learn that Earth's structure is more complex. Our understanding of how the Earth evolved is changing accordingly."

What will Expedition 312 find at the bottom of this very deep hole? We will keep you updated as they report back.