New Model Of Ocean Depths Proves Accurate

March 13, 1997

EVANSTON, Ill. --- Geologists have been trying for more than a decade to account for the discrepancies between their models for how plate tectonics works and the actual depths of the ocean floors.

Now, two geologists, from Northwestern University and the University of Illinois at Chicago, have demonstrated that an adjustment to one of those models --- involving reducing the assumed thickness of the tectonic plate --- allows the model to fit the data much more precisely.

They illustrate the accuracy of the new model with projected and actual ocean depths in the area surrounding the Hawaiian Islands in Friday, March 14th's issue of the journal Science. The two researchers, Carol A. Stein, associate professor of geological sciences at the University of Illinois at Chicago, and Seth Stein, professor of geological sciences at Northwestern University, believe they have demonstrated their model provides a "significantly better fit to the data" than other models currently in use.

Scientists first determined in the late 60s that the earth's surface is covered with some 14 giant plates that move in different directions at a rate of a few inches a year. They have since determined that these plates are formed at mid-ocean ridges by an upswelling of molten rock and move slowly away from these ridges in both directions.

As they inch away from the ridges and age, the plates become deeper and colder, eventually sliding back into the earth's heated interior. This process accounts for some 70 percent of earth's loss of heat from its interior. Another 5 percent is accounted for by "plumes" of molten earth that spout up at a few "hot spots" on the ocean floor, forming chains of islands such as Hawaii.

The plates themselves are called the "lithosphere," and estimates have been that they averaged some 125 kilometers, or 75 miles, in thickness. When geologists developed a model of their movement, based on their speed, age and temperature, the model worked well for regions up to 70 million years old. But seafloor areas older than that were consistently shallower than predicted by the model.

The husband and wife team of Seth and Carol Stein first proposed in an article in Nature in 1992 that if the assumption of the plates' thickness was changed from 125 kilometers to 95 kilometers, the model proved to be far more accurate. Since that time, however, many geologists have continued to use the old models and have expended extensive energy trying to explain its discrepancies.

The Science article refers to this as the "Lake Wobegon Effect." In the radio show "Prairie Home Companion," the mythical town of Lake Wobegon is "where all children are above average." This suggests that there might be something wrong with the standard being applied, as is the case with geologists who attempt to explain the "anomalies" of shallow sea depths while using the wrong model, the authors wrote.

The Science article is accompanied with four charts of a region of the Pacific Ocean that includes Hawaii and the Marshall Islands. One chart is of the actual depth of the ocean floor, and the other three are of projections of that depth using three different models of plate movement. The Stein model, assuming a lithosphere thickness of 95 kilometers, precisely matches the observed depths, except for the chain of islands themselves (which were formed by plumes).


(Media contact Chris Chandler at 847-491-3115, or by e-mail at Stein can be reached at 847-491-5265 or by e-mail at

( Color charts can be obtained from the website at

Northwestern University

Related Ocean Floor Articles from Brightsurf:

Former piece of Pacific Ocean floor imaged deep beneath China
In a study that gives new meaning to the term ''rock bottom,'' seismic researchers have discovered the underside of a rocky slab of Earth's lithosphere that has been pulled more than 400 miles beneath northeastern China by the process of tectonic subduction.

Love waves from the ocean floor
Supercomputer simulations of planetary-scale interactions show how ocean storms and the structure of Earth's upper layers together generate much of the world's seismic waves.

Solving the mystery of carbon on ocean floor
Little bits of black carbon littering the ocean floor, separate and distinct from the organic carbon believed to come from the ocean's surface.

Largest mapping of breathing ocean floor key to understanding global carbon cycle
The largest open-access database of the sediment community oxygen consumption and CO2 respiration is now available.

New threat from ocean acidification emerges in the Southern Ocean
Scientists investigating the effect of ocean acidification on diatoms, a key group of microscopic marine organisms, phytoplankton, say they have identified a new threat from climate change -- ocean acidification is negatively impacting the extent to which diatoms in Southern Ocean waters incorporate silica into their cell walls.

Monitoring CO2 leakage sites on the ocean floor
Injecting carbon dioxide (CO2) deep below the seabed could be an important strategy for mitigating climate change, according to some experts.

Earth recycles ocean floor into diamonds
Most diamonds are made of cooked seabed. The diamond on your finger is most likely made of recycled seabed cooked deep in the Earth.

Otherworldly mirror pools and mesmerizing landscapes discovered on ocean floor
Scientists aboard Schmidt Ocean Institute's research vessel Falkor recently discovered and explored a hydrothermal field at 2,000 meters depth in the Gulf of California where towering mineral structures serve as biological hotspots for life.

MERMAIDs reveal secrets from below the ocean floor
Floating seismometers dubbed MERMAIDs -- Mobile Earthquake Recording in Marine Areas by Independent Divers -- reveal that Galápagos volcanoes are fed by a mantle plume reaching 1,900 km deep.

Delivery method associated with pelvic floor disorders after childbirth
Research completed at Johns Hopkins and the Greater Baltimore Medical Center has demonstrated that vaginal childbirth substantially increases the probability a woman will develop a pelvic floor disorder later in life.

Read More: Ocean Floor News and Ocean Floor Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to