Featured Research

from universities, journals, and other organizations

Earth's Core May Contain "Cold Front" Of Molten Iron

Date:
November 19, 1999
Source:
Johns Hopkins University
Summary:
One of the world's biggest cold fronts might be under our feet rather than over our heads, according to results from earth scientists at The Johns Hopkins University.

One of the world's biggest cold fronts might be under our feet rather than over our heads, according to results from earth scientists at The Johns Hopkins University.

Writing in this week's issue of "Science," Hopkins researchers describe a laboratory experiment designed to model conditions in the outer core of the Earth, which is composed of molten iron. The laboratory results point to the possibility that a thin jet of relatively cold molten iron is streaming down across the liquid outer core from an area in the mid-Pacific to Earth's solid iron inner core.

Ikuro Sumita, a postdoctoral researcher at Hopkins and lead author on the paper, cautions that the new model is a "working hypothesis" and that there are many questions and concerns still to be addressed. But he has developed several tantalizingly direct ways to use the model to answer questions about observations relating to the Earth's core.

The Earth's molten outer core lies beneath the rocky mantle, which includes the surface. Earth scientists think of the mantle as the "master" that directs the activity of the outer core, which acts like a "slave" in response. Because of this close relationship, understanding the core's activity should help scientists better understand the mantle's behavior.

It's not possible, however, to directly observe the outer core. Scientists can image the solid inner core using energy from earthquakes, known as seismic waves. But this reveals little of the liquid outer core.

"What we have to rely on instead to study the outer core is Earth's magnetic field, which is produced by the flow of molten iron," says Sumita.

Scientists can link changes in the strength and direction of magnetic fields above ground to the ebb and flow of molten iron below ground, Sumita explains. "For example, we can interpret the westward motion of the magnetic field patches as a manifestation of the westward flow in the core," he notes.

For their study, Sumita and co-author Peter Olson, professor of earth and planetary sciences, modeled flow patterns in the Earth's core using a water-filled, rotating hemisphere with a solid chilled sphere at its center. A heater was placed at one spot on the rim of the hemisphere to imitate the uneven transfer of heat between the mantle and the outer core. Because the direction of the centrifugal force in the experiment is opposite to that of the Earth's gravity, this heat source corresponds to a cold region found in the lower mantle of the Earth which causes a downward flow in the core.

Researchers set the model rotating, injected a fluorescent dye into the water, and filmed the resulting patterns. A thin spiral-shaped jet moving opposite the direction of the rest of the water soon emerged. In a manner similar to a weather front, the jet, which spiraled down to the solid sphere at the model's center, marked out the boundary between hot, high pressure areas and cool, low pressure zones in the water.

"We know that the seismic waves travel unusually fast in the lowermost region of the mantle beneath East Asia," says Sumita. "This is often interpreted as being due to a cold plate which has sunk into the bottom of the mantle from the surface of the Earth. Such a cold region would cause the core to lose a great deal of heat there."

A spiraling jet of cold iron starting east of that area could account for irregularities in the magnetic patterns observed over the Pacific. For example, there are fewer westward driftingmagnetic patches in this area, which could be a result of the front blocking the westward flow of iron as well as the upward flow of hot iron.

"It may be that the colder mass of fluid west of the front causes the iron to solidify more in one region and accounts for this uneven east-west buildup," Sumita explains.

Missing in Sumita's theory is a mechanism that would keep the cold spot in East Asia cold for a long time. The buildup in the Earth's inner core is very slow, and to have shaped that buildup the spiral would need to have been in place for millions of years.

Another potential wrinkle is the possibility that solid inner core rotates, in which case the buildup should be more even.

"To follow up," Sumita says, "I will have to summarize the conditions needed for the existence of this jet and the front based upon the experiments I did with different heater magnitudes and sizes."

Further evidence on the potential merits of Sumita and Olson's model could come from high-resolution seismic imaging of the structure of the lowermost mantle and the inner core. Olson published a study in "Nature" last week that examined the flow near the polar region of the outer core. That study is complementary to the present work, which examines the flow in the lower latitudes of the outer core.

Sumita's research was supported by the Research Fellowships of the Japan Society for the Promotion of Science for Young Scientists. The experiments were supported by the Geophysics Program of the National Science Foundation.

###


Story Source:

The above story is based on materials provided by Johns Hopkins University. Note: Materials may be edited for content and length.


Cite This Page:

Johns Hopkins University. "Earth's Core May Contain "Cold Front" Of Molten Iron." ScienceDaily. ScienceDaily, 19 November 1999. <www.sciencedaily.com/releases/1999/11/991118160149.htm>.
Johns Hopkins University. (1999, November 19). Earth's Core May Contain "Cold Front" Of Molten Iron. ScienceDaily. Retrieved August 28, 2014 from www.sciencedaily.com/releases/1999/11/991118160149.htm
Johns Hopkins University. "Earth's Core May Contain "Cold Front" Of Molten Iron." ScienceDaily. www.sciencedaily.com/releases/1999/11/991118160149.htm (accessed August 28, 2014).

Share This




More Earth & Climate News

Thursday, August 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Killer Amoeba Found in Louisiana Water System

Killer Amoeba Found in Louisiana Water System

AP (Aug. 28, 2014) State health officials say testing has confirmed the presence of a killer amoeba in a water system serving three St. John the Baptist Parish towns. (Aug. 28) Video provided by AP
Powered by NewsLook.com
Scientists Have Figured Out Why Rocks Move In Death Valley

Scientists Have Figured Out Why Rocks Move In Death Valley

Newsy (Aug. 28, 2014) The mystery of the moving rocks in Death Valley, California, has finally been solved. Scientists are pointing to a combo of water, ice and wind. Video provided by Newsy
Powered by NewsLook.com
Big Waves, Minor Flooding from Hurricane

Big Waves, Minor Flooding from Hurricane

AP (Aug. 27, 2014) Thundering surf spawned by Hurricane Marie pounded the Southern California coast Wednesday, causing minor flooding in a low-lying beach town. High surf warnings were posted for Los Angeles County south through Orange County. (Aug. 27) Video provided by AP
Powered by NewsLook.com
Calif. Quake Underscores Need for Early Warning

Calif. Quake Underscores Need for Early Warning

AP (Aug. 26, 2014) Researchers at UC Berkeley are testing a prototype of an earthquake early warning system that California is pursuing years after places like Mexico and Japan already have them up and running. (August 26) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins