Featured Research

from universities, journals, and other organizations

Researchers Investigate Mysteries Of The African Rift

Date:
December 13, 2001
Source:
Penn State
Summary:
The formation and evolution of the African Rift Valley are shaded in mystery, but geoscientists at Penn State are mapping the history of the Rift through space and time by analyzing the chemistry of ancient lava from Lake Turkana, northern Kenya.

San Francisco, Cal. -- The formation and evolution of the African Rift Valley are shaded in mystery, but geoscientists at Penn State are mapping the history of the Rift through space and time by analyzing the chemistry of ancient lava from Lake Turkana, northern Kenya.

Related Articles


"We know what the lavas at Turkana look like today and we know what the lavas looked like 35 million years ago in Ethiopia," says Dr. Tanya Furman, associate professor of geosciences. "We also know where the Afar plume is today, but we don't know what it looked like 35 million years ago. The only place we can go back more than 30 million years is in Turkana."

Furman and Kelly Knight, graduate student in geosciences, are looking at the chemical signatures of lavas from the Rift Valley in Turkana to understand the evolution of mantle plumes and how continents split apart.

A mantle plume is a jet of molten lava from the Earth's mantle that reaches the Earth's surface, but is independent of the motion of the tectonic plates. Typically, when mantle plumes rise under oceans, they form islands. The Hawaiian Islands were formed by a plume which remains stationary while the Pacific plate moves above it, creating a string of islands in its wake.

When a plume appears under a continent, a rift may form. Eventually, an important transformation takes place, the rift splits the continent in two, creating an ocean and the rift itself comes a mid ocean ridge. Mid ocean ridges are the boundaries of two plates and are connected to the Earth's tectonic activity. While geoscientists know the general history of continental rifting, exactly when a rift becomes a ridge and when it becomes part of the tectonic system is unknown.

The African Rift Valley runs in eastern Africa from the junction of the Red Sea and the Gulf of Aden southward to Malawi where it gradually disappears.

"Some of what we found is consistent with the presence of a plume in Turkana about 35 million years ago," Knight told attendees at the fall meeting of the American Geophysical Union today (Dec. 13) in San Francisco. "We know the plume was in the Ethiopia Sudan area and it appears that lava was channeled 1000 or more kilometers beneath or through the lithosphere to Turkana."

Turkana is the best place to look at the chemistry of the old lava because three successive rifting events have occurred in the area, stretching and thinning the Earth's crust. While the rest of the Rift has a crust of 100 kilometers with a layer of chemically unusual rocks stuck on the bottom, Turkana has only about 20 kilometers of crust.

The researchers are looking at the chemistry of the lavas including major and minor components, trace elements and isotopes. The recent findings are based on the ratios of trace elements in the lavas, including zirconium to niobium, uranium to thorium, lanthanum to niobium and barium to niobium. The trace elements in the lavas are related to the source rocks that were melted by the plume. By tracing the lavas back to the rocks, the researchers can trace the paths of the lavas in space. By looking at the old lava in the Turkana area, the researchers can trace the lavas in time.

"We choose trace element ratios that are indicative of the source region of the rocks," says Furman. "These data, plus our preliminary neodymium isotope analyses, suggest that plume lavas have been erupting at Turkana for perhaps 35 million years." The researchers are also waiting for the results of isotope studies using strontium, and lead to clarify the chemical structure of the plume.

The African Rift Valley is a heavily seismic area and there have been volcanic eruptions in the past 50 years. The area is actively changing, but while Furman and Knight know that the rift north of Ethiopia is now an ocean ridge and that the rift south of Turkana is not, they still do not know when, where and how the change from mantle plume to mid ocean ridge occurs.


Story Source:

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


Cite This Page:

Penn State. "Researchers Investigate Mysteries Of The African Rift." ScienceDaily. ScienceDaily, 13 December 2001. <www.sciencedaily.com/releases/2001/12/011213084056.htm>.
Penn State. (2001, December 13). Researchers Investigate Mysteries Of The African Rift. ScienceDaily. Retrieved December 20, 2014 from www.sciencedaily.com/releases/2001/12/011213084056.htm
Penn State. "Researchers Investigate Mysteries Of The African Rift." ScienceDaily. www.sciencedaily.com/releases/2001/12/011213084056.htm (accessed December 20, 2014).

Share This


More From ScienceDaily



More Earth & Climate News

Saturday, December 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Lava on Track to Hit Hawaii Market

Raw: Lava on Track to Hit Hawaii Market

AP (Dec. 19, 2014) Lava from an active volcano on Hawaii's Big Island slowed slightly but stayed on track to hit a shopping center in the small town of Pahoa. (Dec. 19) Video provided by AP
Powered by NewsLook.com
Birds Might Be Better Meteorologists Than Us

Birds Might Be Better Meteorologists Than Us

Newsy (Dec. 19, 2014) A new study suggests a certain type of bird was able to sense a tornado outbreak that moved through the U.S. a day before it hit. Video provided by Newsy
Powered by NewsLook.com
Navy Unveils Robot Fish

Navy Unveils Robot Fish

Reuters - Light News Video Online (Dec. 18, 2014) The U.S. Navy unveils an underwater device that mimics the movement of a fish. Tara Cleary reports. Video provided by Reuters
Powered by NewsLook.com
Arctic Warming Twice As Fast As Rest Of Planet

Arctic Warming Twice As Fast As Rest Of Planet

Newsy (Dec. 18, 2014) The Arctic is warming twice as fast as the rest of the planet, thanks in part to something called feedback. Video provided by Newsy
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