Oxidized lava may help explain Earth's evolution

Jul 30, 2009 By RANDOLPH E. SCHMID , AP Science Writer
Lava pours out of Montserrat during an eruption. Image: University of Arkansas

(AP) -- Material from volcanoes where the Earth's plates squeeze together is more oxidized than in regions where the seafloor splits apart, a finding that helps shed light on some of the basic processes in the planet's mantle.

Using highly sensitive X-ray techniques researchers were able to measure the amount of reaction with oxygen that had occurred in minerals in various situations.

Oxidation, best known as rust when it affects metals, was low in materials erupting from mid-ocean ridges where the seafloor spreads apart, Katherine A. Kelley of the University of Rhode Island and Elizabeth Cottrell of the Smithsonian's National Museum of Natural History report in Friday's edition of the journal Science.

But higher rates were found in produced by arc volcanoes, which occur in areas where the Earth's collide, with one sliding below another, they found.

"The seafloor is kind of like a rust conveyor belt," Cottrell said in a telephone interview. As material moves over millions of years from the mid-ocean ridges to the subduction zones it becomes increasingly oxidized.

This indicates that what happens on the Earth's surface influences what goes on beneath, Cottrell said, and things that are happening in geology today probably have also done so in the past.

"This is a step in looking at the long-term evolution of the planet," she said.

The finding firmly establishes that subduction oxidizes the source of magma for arc volcanoes, "but the long-term consequences for the evolution of Earth remain poorly understood," commented Marc M. Hirschmann of the University of Minnesota, who was not part of the research team.

The researchers made their calculations by studying water trapped in tiny particles, Cottrell said, but that doesn't mean that the is causing the oxidation. While water causes rust in the atmosphere it is much less effective at doing that under high pressure such as on the .

The research was supported by the National Science Foundation and the Department of Energy.

---

On the net:

Science: http://www.sciencemag.org

©2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Explore further: Suomi NPP satellite spots birth of Tropical Cyclone Kate

add to favorites email to friend print save as pdf

Related Stories

The great recycler -- planet Earth

Jun 09, 2007

In the current edition of leading science journal Nature, an international team of researchers publishes proof that the Earth recycles portions of its own crust, driving it deep down into the mantle of the ...

Evidence of volcanic eruptions deep beneath the Arctic Ocean

Jun 25, 2008

A research team led by the Woods Hole Oceanographic Institution (WHOI) has uncovered evidence of explosive volcanic eruptions deep beneath the ice-covered surface of the Arctic Ocean. Such violent eruptions of splintered, ...

Lava provides window on early Earth

Nov 02, 2007

Researchers at Harvard and the University of Hawaii believe they’ve resolved a long-standing controversy over the roots of islands — volcanoes in the middle of tectonic plates — showing that the islands’ ...

Recommended for you

Suomi NPP satellite spots birth of Tropical Cyclone Kate

16 hours ago

The tropical low pressure area previously known as System 95S organized and strengthened into Tropical Cyclone Kate on Dec. 24 and the Cocos Keeling Islands are expected to feel its effects on Dec. 25 and ...

NASA looks at some severe holiday weather from space

16 hours ago

Severe weather in the form of tornadoes is not something people expect on Christmas week but a storm system on Dec. 23 brought tornadoes to Mississippi, Georgia and Louisiana. As the storm moved, NASA's RapidScat ...

NASA satellite spots Christmas

21 hours ago

If you're looking for Christmas NASA's Aqua satellite spotted it in the Southern Indian Ocean. It's a coral atoll (a ring-shaped reef, island, or chain of islands made up of coral) in the northern Line Islands ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

omatumr
1 / 5 (2) Jul 30, 2009
MID-OCEAN RIDGE BASALTS ARE MORE PRIMITIVE

This is an interesting story.

As I recall the noble gas record in lavas from arc volcanoes is also distinct from that in MORBs (Mid-Ocean Ridge Basalts).

MORBs contain primordial He and Ne (leaking from the lower mantle) mixed with highly radiogenic Ar-40 from the decay of K-40, radiogenic Xe-129 from the decay of extinct I-129, and fissiogenic Xe-136 from the decay of U-238 and extinct Pu-244 in the upper, depleted mantle.

See: 1. "The xenon record of extinct radioactivities in the Earth," Science 174 (1971) 1334-1336 http://tinyurl.com/nnjh4v and
2. "The noble gas record of the terrestrial planets", Geochemical Journal 15 (1981) 247-267 http://tinyurl.com/2k8ds3

With kind regards,
Oliver K. Manuel
http://www.omatumr.com
out7x
1 / 5 (1) Jul 31, 2009
Sea floor spreading is new crust. Subduction is old crust. Nothing new here.

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.