Featured Research

from universities, journals, and other organizations

Iron in Earth's core weakens before melting

Date:
October 10, 2013
Source:
University College London
Summary:
The iron in Earth's inner core weakens dramatically before it melts, explaining the unusual properties that exist in the moon-sized solid center of our planet that have, up until now, been difficult to understand.

The iron in Earth's inner core weakens dramatically before it melts, explaining the unusual properties that exist in the moon-sized solid center of our planet that have, up until now, been difficult to understand.
Credit: iStockphoto

The iron in the Earth's inner core weakens dramatically before it melts, explaining the unusual properties that exist in the moon-sized solid centre of our planet that have, up until now, been difficult to understand.

Related Articles


Scientists use seismic waves -- pulses of energy generated during earthquakes -- to measure what is happening in the Earth's inner core, which at 6000 km beneath our feet is completely inaccessible.

Problematically for researchers, the results of seismic measurements consistently show that these waves move through the Earth's solid inner core at much slower speeds than predicted by experiments and simulations.

Specifically, a type of seismic wave called a 'shear wave' moves particularly slowly through the Earth's core relative to the speed expected for the material -- mainly iron -- from which the core is made. Shear waves move through the body of the object in a transverse motion -- like waves in a rope, as opposed to waves moving through a slinky spring.

Now, in a paper published in Science, scientists from UCL have proposed a possible explanation. They suggest that the iron in the Earth's core may weaken dramatically just before melting, becoming much less stiff. The team used quantum mechanical calculations to evaluate the wave velocities of solid iron at inner-core pressure up to melting.

They calculated that at temperatures up to 95% of what is needed to melt iron in the Earth's inner core, the speed of the seismic waves moving through the inner core decreases linearly but, after 95%, it drops dramatically.

At about 99% of the melting temperature of iron, the team's calculated velocities agree with seismic data for the Earth's inner core. Since independent geophysical results suggest that the inner core is likely to be at 99-100% of its melting temperature, the results presented in this paper give a compelling explanation as to why the seismic wave velocities are lower than those predicted previously.

Professor Lidunka Vočadlo, from the UCL department of Earth Sciences and an author of the paper said: "The Earth's deep interior still holds many mysteries that scientists are trying to unravel.

"The proposed mineral models for the inner core have always shown a faster wave speed than that observed in seismic data. This mismatch has given rise to several complex theories about the state and evolution of the Earth's core."

The authors stress that this is not the end of the story as other factors need to be taken into account before a definitive core model can be made. As well as iron, the core contains nickel and light elements, such as silicon and sulphur.

Professor Vočadlo said: "The strong pre-melting effects in iron shown in our paper are an exciting new development in understanding the Earth's inner core. We are currently working on how this result is affected by the presence of other elements, and we may soon be in a position to produce a simple model for the inner core that is consistent with seismic and other geophysical measurements. "


Story Source:

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


Journal Reference:

  1. Benjamν Martorell*, Lidunka Vočadlo, John Brodholt, Ian G. Wood. Strong Premelting Effect in the Elastic Properties of hcp-Fe Under Inner-Core Conditions. Science, 2013 DOI: 10.1126/science.1243651

Cite This Page:

University College London. "Iron in Earth's core weakens before melting." ScienceDaily. ScienceDaily, 10 October 2013. <www.sciencedaily.com/releases/2013/10/131010142750.htm>.
University College London. (2013, October 10). Iron in Earth's core weakens before melting. ScienceDaily. Retrieved November 26, 2014 from www.sciencedaily.com/releases/2013/10/131010142750.htm
University College London. "Iron in Earth's core weakens before melting." ScienceDaily. www.sciencedaily.com/releases/2013/10/131010142750.htm (accessed November 26, 2014).

Share This


More From ScienceDaily



More Earth & Climate News

Wednesday, November 26, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Bolivian Recycling Initiative Turns Plastic Waste Into School Furniture

Bolivian Recycling Initiative Turns Plastic Waste Into School Furniture

Reuters - Innovations Video Online (Nov. 26, 2014) — Innovative recycling project in La Paz separates city waste and converts plastic garbage into school furniture made from 'plastiwood'. Tara Cleary reports. Video provided by Reuters
Powered by NewsLook.com
Blu-Ray Discs Getting Second Run As Solar Panels

Blu-Ray Discs Getting Second Run As Solar Panels

Newsy (Nov. 26, 2014) — Researchers at Northwestern University are repurposing Blu-ray movies for better solar panel technology thanks to the discs' internal structures. Video provided by Newsy
Powered by NewsLook.com
Antarctic Sea Ice Mystery Thickens... Literally

Antarctic Sea Ice Mystery Thickens... Literally

Newsy (Nov. 25, 2014) — Antarctic sea ice isn't only expanding, it's thicker than previously thought, and scientists aren't sure exactly why. Video provided by Newsy
Powered by NewsLook.com
3D Map of Antarctic Sea Ice to Shed Light on Climate Change

3D Map of Antarctic Sea Ice to Shed Light on Climate Change

Reuters - Innovations Video Online (Nov. 24, 2014) — A multinational group of scientists have released the first ever detailed, high-resolution 3-D maps of Antarctic sea ice. Using an underwater robot equipped with sonar, the researchers mapped the underside of a massive area of sea ice to gauge the impact of climate change. Ben Gruber reports. Video provided by Reuters
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:

Strange & Offbeat Stories

 

Plants & Animals

Earth & Climate

Fossils & Ruins

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