Study may solve age-old mystery of missing chemicals from Earth's mantle

Dec 05, 2007

Observations about the early formation of Earth may answer an age-old question about why the planet’s mantle is missing some of the matter that should be present, according to UBC geophysicist John Hernlund.

Earth is made from chondrite, very primitive rocks of meteorites that date from the earliest time of the solar system before the Earth was formed. However, scientists have been puzzled why the composition of Earth’s mantle and core differed from that of chondrite.

Hernlund’s findings suggest that an ancient magma ocean swirled beneath the Earth’s surface and would account for the discrepancy.

“As the thick melted rock cooled and crystallized, the solids that resulted had a different composition than the melt,” explains Hernlund, a post-doctoral fellow at UBC Earth and Ocean Sciences.

“The melt held onto some of the elements. This would be where the missing elements of chondrite are stored.”

He says this layer of molten rock would have been around 1,000 km thick and 2,900 km beneath the surface.”

Published in today’s edition of the journal Nature, Hernlund’s study explores the melting and crystallization processes that have controlled the composition of the Earth's interior over geological time. Co-authors are Stéphane Labrosse, Ecole Normale Superieure de Lyon and Nicolas Coltice, Université de Lyon.

The centre of Earth is a fiery core of melted heavy metals, mostly iron. This represents 30 per cent while the remaining 70 per cent is the outer mantle of solid rock.

Traditional views hold that a shallow ocean of melted rock (magma) existed 1,000 km below the Earth’s surface, but it was short lived and gone by 10 million years after the formation of Earth.

In contrast, Hernlund’s evolutionary model predicts that during Earth’s hotter past shortly after its formation 4.5 billion years ago, at least one-third of the mantle closest to the core was also melted.

Source: University of British Columbia

Explore further: Ancient deformation of the lithosphere revealed in Eastern China

add to favorites email to friend print save as pdf

Related Stories

Gully patterns document Martian climate cycles

Jan 28, 2015

Geologists from Brown University have found new evidence that glacier-like ice deposits advanced and retreated multiple times in the midlatitude regions of Mars in the relatively recent past.

Dawn spacecraft captures best-ever view of dwarf planet

Jan 27, 2015

NASA's Dawn spacecraft has returned the sharpest images ever seen of the dwarf planet Ceres. The images were taken 147,000 miles (237,000 kilometers) from Ceres on Jan. 25, and represent a new milestone for ...

Uranium isotopes reveal age and origin of volcanic rocks

Jan 20, 2015

From the beginning of time, uranium has been part of the Earth and, thanks to its long-lived radioactivity, it has proven ideal to date geological processes and deduce Earth's evolution. Natural uranium consists ...

Recommended for you

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

brant
1 / 5 (3) Dec 05, 2007
"why the planets mantle is missing some of the matter that should be present,"

Is an assumption that your model accurately represents reality.

Obviously it doesnt.
Time to look at your model instead of forcing some other results to fit your models lacking.
out7x
2 / 5 (3) Dec 06, 2007
Petrology is a major field of study in geology.
Trippy
5 / 5 (1) Jan 24, 2008
Yeah... Imagine the audacity of suggesting that the melted area might have been bigger then previously expected, the sheer nerve of someone suggesting that mixing might have occured in a liquid, and that differential crystalization might actually have occured.

(For anyone who's in doubt - Wiki's page on it http://en.wikiped..._melting )

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.