Bernard Coakley

Bernard Coakley, a marine geologist with the University of Alaska at Fairbanks, writes from the Arctic Ocean, where his team is reconstructing the geologic history of the Chukchi Shelf and the Chukchi Borderland.

Tuesday, Sept. 13

A few nights ago, the sky turned clear, revealing a full moon and the northern lights. The lights were understated, a double silver ribbon snaking across the sky, but everyone on the midnight watch turned out to see them. Most people have never been this far north. The lights are emblematic of how different this place is and how far we have traveled to encounter it. The gorgeous weather has stayed with us for the last two days — calm seas and sunny warm days have been perfect to deploy our multichannel seismic reflection gear and begin acquiring data.

When I talk about exploring the Arctic Ocean, the question of “why” comes up. Why go all that way north? Why collect those data? Sometimes, enmeshed in the rush of activity and preparation and the minutiae of actually doing this work, it is easy to forget the reasons that motivate us and justify the investment of time and money. So, “Why the Chukchi?”

It is our good fortune to study a relatively unknown area. Some places in the oceans have been visited repeatedly. There are large data sets of various types and vintages. The simple questions have been answered. You have to be an expert and even a relatively specialized expert to appreciate the active discussions about the history and active processes in these places. In much of the Arctic Ocean, these simple questions are still unresolved. So the discussion can start with very basic concepts.

Bernard Coakley

When I teach Geology 101 at the University of Alaska Fairbanks, I like to begin each lecture with a very simple concept that should cause you to take a very different view of your world. Here is one: Every point on the surface of this earth is in motion. There are no fixed points. This is one of the basic insights from the plate tectonic revolution. The rates of motion vary widely, from millimeters to more than 10 centimeters per year, relative to the earth’s center. These rates are something like how fast your fingernails grow.

Another basic principle is that the continents and the oceans are made up of different material, formed by distinct processes and destined for different fates. The continents stand high, above sea level, because they are thick. The oceanic crust rides low and is mostly submerged because it is thin and made of denser material than the continents. In this view, the continents are permanent (more or less) and old, and the oceans relatively young and temporary.

At the midocean ridges, the oceans expand and grow over time. The mid-Atlantic ridge, which separates North America and South America from Europe and Africa, is one. The continents on opposite sides of this active ridge continue to separate. If the ocean is growing and the surface area (or volume) of the planet is not increasing, it is necessary that an equal amount of oceanic crust is being destroyed elsewhere. Destruction of oceanic crust, the recycling of this material back into the earth’s interior, is accomplished at subduction zones. These zones underlie the famous “ring of fire” that surrounds much of the Pacific Ocean. The volcanoes are one expression of this active recycling.

Armed with the basics of plate tectonics, we are prepared to begin to understand the Arctic Ocean, which can be regarded as the last pocket of resistance to this scientific revolution. The Arctic Ocean can be divided into two primary basins, the Eurasian Basin and the Amerasian Basin. The Eurasian Basin formed when the mid-Atlantic Ridge grew to the north and divided a long, narrow strip of continental crust, the Lomonosov Ridge, from the Barents Shelf. Steady separation of the Lomonosov, which could be thought of as being like Baja California after 60 million years, from northern Europe created the Eurasia Basin. The Gakkel Ridge, the midocean ridge responsible for this separation, is still active today.

On the opposite side of the Lomonosov Ridge is the Amerasian Basin. Siberia, the Canadian Arctic Islands and northern Alaska define the edges of this basin. In contrast to the Eurasian Basin, which has formed during the Cenozoic, the Amerasian Basin formed during the Mesozoic, also known as the age of the dinosaurs. Ignoring a few small earthquakes near the United States-Canada border in northeast Alaska, the basin is inactive today. So far as we know, it has not been active for some time. Tectonic activity, deformation of rock largely indicated by earthquakes, is mostly confined to plate boundaries. We do not know the location or orientation of these fossil plate boundaries in the Amerasian Basin. As a result we do not understand when and how the basin formed.

To a great extent, the plate tectonic revolution was about understanding the oceans. It has also helped us understand the continents. The Appalachian Mountains, which formed by closing an ocean basin, make much more sense when you know that the Atlantic Ocean is, in geologic terms, a temporary feature. Without a clear history of the Amerasian Basin, we have been forced to stand on the edges of this ocean and, by examining the rocks exposed there, develop inferences about the history of the basin. This is the exact opposite of how continental geology has been done anywhere else in the world for the last 40 years. The prime objective of this cruise is to reveal in detail a part of the Arctic Ocean and test the basic models we have for the development of the Amerasian Basin.