Featured Research

from universities, journals, and other organizations

Like A Balloon: Study Supports Buoyancy Explanation For How Volcanic Rock Rises Through The Earth's Mantle

Date:
August 31, 2001
Source:
Georgia Institute Of Technology
Summary:
A new study of the Earth's mantle beneath the ocean near Iceland provides the most convincing evidence yet that simple buoyancy of hot, partially molten rocks can play an important role in causing them to rise and erupt through the surface at mid-ocean ridges.

A new study of the Earth's mantle beneath the ocean near Iceland provides the most convincing evidence yet that simple buoyancy of hot, partially molten rocks can play an important role in causing them to rise and erupt through the surface at mid-ocean ridges.

Related Articles


Published August 31 in the journal Science, the Georgia Institute of Technology study also shows that heat from a volcanic hotspot in Iceland can affect normal mantle convection activities at a nearby ridge.

The motion of the Earth's surface plates is driven by a convection cycle in which cold material sinks into the deep mantle and hot material rises toward the surface. At most mid-ocean ridges, scientists believe that hot rock rises passively to fill the gap created by the separation - or spreading - of the plates.

But a detailed analysis of seismic waves passing through regions of upwelling rock provides new evidence that another mechanism -- buoyancy much like that of a hot-air balloon - helps drive partially melted rocks from the Earth's mantle up to the surface at these ridges. The effect is especially pronounced at the Reykjanes Ridge, a portion of the mid-Atlantic ridge that gains significant heating from Iceland's volcanic hotspot. This additional heating adds 30-80 Kelvin to the mantle temperature there and may play an important role in powering the buoyancy at this location.

"These observations imply that the volcanic rocks erupting on the surface forced their way through the upper 60-100 kilometers of the Earth through the power of their own buoyancy," said James B. Gaherty, author of the paper and an assistant professor in Georgia Tech's School of Earth & Atmospheric Sciences. "You can envision this like a hot-air balloon that bursts through its hangar roof rather than waiting for the rooftop door to open. This contrasts with most spreading centers, in which the hot rocks reach the surface simply to fill the void left by the spreading plates."

Gaherty studied seismic waves from 17 earthquakes as they passed through the Reykjanes Ridge. Waves with vertical polarizations passed through the region at the speed expected. However, transversely polarized waves were delayed, providing Gaherty information about how the orientation of crystalline structures in the region may have been deformed by the mantle flow.

"The propagation speed of these waves provides information about two critical Earth parameters: the relative temperature of the rocks beneath the ridge and the crystalline structure or fabric embedded in the rocks as they have deformed during convection," he explained. "In this case the fabric is consistent with buoyancy-driven upwelling of the partially melted rock."

Because the ridge is adjacent to a volcanic hotspot on Iceland, the study also provides new information on how such heat sources affect ridges - and may prompt reconsideration of existing models that explain such sea-floor spreading. For example, Gaherty found that heating from the Iceland hot spot extended to a depth of at least 100 kilometers.

Though Gaherty's study was confined to the Reykjanes Ridge, he believes buoyancy may also play a role in ridge dynamics for other areas.

"It provides unique observational evidence that buoyancy-driven upwelling is an important component of ridge dynamics, especially in environments where passive sea-floor spreading is too slow to accommodate melt production," he writes. "The presence of anomalous mantle fabric to about 100-kilometer depth implies that the hotspot modulates upper-mantle dynamics beneath the ridge to at least this depth."

Earth scientists have previously discussed buoyancy as a mechanism for powering volcanic upwelling, but direct evidence for it had been limited. "This paper provides some of the most direct evidence to date," Gaherty said.

The study also provides additional information about the thermal anomaly associated with the Iceland mantle plume, which has been the topic of significant study. Further, it provides more evidence that slow-spreading ridge structures in the Atlantic differ in important ways from comparable but faster-spreading structures in the Pacific.

Gaherty's work focuses on understanding the connection between solid-state convection in the Earth's mantle -- a solid rock region extending from 30 to 3,000 kilometers in depth - and surface deformation and plate tectonics.

Hot upwelling of volcanic rock from the mantle typically occurs in two environments: (1) mid-ocean ridges, which are linear chains of volcanic activity along the boundary where two plates move away from one another, and (2) "hotspots," which are point sources of high volcanic output associated with quasi-stationary and long-lived heat sources in the mantle. The mid-Atlantic ridge is an example of the former; Hawaii, Iceland and Yellowstone National Park are examples of the latter.

The research was sponsored by the National Science Foundation.


Story Source:

The above story is based on materials provided by Georgia Institute Of Technology. Note: Materials may be edited for content and length.


Cite This Page:

Georgia Institute Of Technology. "Like A Balloon: Study Supports Buoyancy Explanation For How Volcanic Rock Rises Through The Earth's Mantle." ScienceDaily. ScienceDaily, 31 August 2001. <www.sciencedaily.com/releases/2001/08/010831081237.htm>.
Georgia Institute Of Technology. (2001, August 31). Like A Balloon: Study Supports Buoyancy Explanation For How Volcanic Rock Rises Through The Earth's Mantle. ScienceDaily. Retrieved November 25, 2014 from www.sciencedaily.com/releases/2001/08/010831081237.htm
Georgia Institute Of Technology. "Like A Balloon: Study Supports Buoyancy Explanation For How Volcanic Rock Rises Through The Earth's Mantle." ScienceDaily. www.sciencedaily.com/releases/2001/08/010831081237.htm (accessed November 25, 2014).

Share This


More From ScienceDaily



More Earth & Climate News

Tuesday, November 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

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
Car Park Solution for Flexible Green Energy

Car Park Solution for Flexible Green Energy

Reuters - Innovations Video Online (Nov. 24, 2014) — A British solar power start-up says that by covering millions of existing car park spaces around the UK with flexible solar panels, the country's power problems could be solved. Suzannah Butcher reports. Video provided by Reuters
Powered by NewsLook.com
Yellow-Spotted Turtles Rescued from Trafficking

Yellow-Spotted Turtles Rescued from Trafficking

Reuters - Light News Video Online (Nov. 24, 2014) — Hundreds of Amazon River turtles released into the wild in Peru. Sharon Reich 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