Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Discovered: World’s Largest Tsunami Debris

25.09.2008
A line of massive boulders on the western shore of Tonga may be evidence of the most powerful volcano-triggered tsunami found to date.

Up to 9 meters (30 feet) high and weighing up to 1.6 million kilograms (3.5 million pounds), the seven coral boulders are located 100 to 400 meters (300 to 1,300 feet) from the coast. The house-sized boulders were likely flung ashore by a wave rivaling the 1883 Krakatau tsunami, which is estimated to have towered 35 meters (115 feet) high.

“These could be the largest boulders displaced by a tsunami, worldwide,” says Matthew Hornbach of the University of Texas Institute for Geophysics. “Krakatau’s tsunami was probably not a one-off event.”

Hornbach and his colleagues will discuss these findings on Sunday, 5 October 2008, at the Joint Annual Meeting of the Geological Society of America (GSA), Soil Science Society of America (SSSA), American Society of Agronomy (ASA), Crop Science Society of America (CSSA), and the Gulf Coast Association of Geological Societies (GCAGS), in Houston, Texas, USA.

Called erratic boulders, these giant coral rocks did not form at their present location on Tongatapu, Tonga’s main island. Because the island is flat, the boulders could not have rolled downhill from elsewhere. The boulders are made of the same reef material found just offshore, which is quite distinct from the island’s volcanic soil. In fact, satellite photos show a clear break in the reef opposite one of the biggest boulders. And some of the boulders’ coral animals are oriented upside down or sideways instead of toward the sun, as they are on the reef.

Hornbach says the Tongatapu boulders may have reached dry land within the past few thousand years. Though their corals formed roughly 122,000 years ago, they are capped by a sparse layer of soil. And the thick volcanic soils that cover most of western Tongatapu are quite thin near the boulders. This suggests the area was scoured clean by waves in the recent past. Finally, there is no limestone pedestal at the base of the boulders, which should have formed as rain dissolved the coral if the boulders were much older.

Many tsunamis, like the one that struck the Indian Ocean in 2004, are caused by earthquakes. But the boulders’ location makes an underwater eruption or submarine slide a more likely culprit. A chain of sunken volcanoes lies just 30 kilometers (20 miles) west of Tongatapu. An explosion or the collapse of the side of a volcano such as that seen at the famous Krakatau eruption in 1883 could trigger a tremendous tsunami.

Another possibility is that a storm surge could have brought the boulders ashore. But that scenario isn’t likely. No storms on record have moved rocks this big. Another possibility is that a monster undersea landslide caused the tsunami. But Hornbach’s analyses of adjacent seafloor topography point to a volcanic flank collapse as the most probable source of such a wave.

“We think studying erratic boulders is one way of getting better statistics on mega-tsunamis,” Hornbach says. “There are a lot of places that have similar underwater volcanoes and people haven’t paid much attention to the threat.” The researchers have already received reports of more erratic boulders from islands around the Pacific. Future study could indicate how frequently these monster waves occur and which areas are at risk for future tsunamis.

The boulders are such an unusual part of the Tongan landscape that tales of their origins appear in local folklore. According to one legend, the god Maui hurled the boulders ashore in an attempt to kill a giant man-eating fowl.

And though many other Pacific islanders follow the custom of heading uphill after earthquakes, Tongans have no such teachings. Such lore may be useless for near-shore volcanically-generated tsunamis, which arrive too quickly for people to evacuate. Instead, most of Tongatapu’s settlements are huddled together on the northern side of the island—away from the brunt of the tsunami threat.

**WHEN & WHERE**

Sunday, 5 October 2008, 8:00 AM-4:45 PM (authors scheduled from 3:00-4:45 PM)
View abstract, Paper 149-8: “Unraveling the Source of Large Erratic Boulders on Tonga: Implications for Geohazards and Mega-Tsunamis” at
http://gsa.confex.com/gsa/2008AM/finalprogram/abstract_149849.htm
George R. Brown Convention Center: Exhibit Hall E (poster, booth 202)
**CONTACT INFORMATION**
For on-site assistance during the 2008 Joint Annual Meeting, 5-9 October, contact Christa Stratton or Sara Uttech in the Newsroom, George R. Brown Convention Center, Room 350B, +1-713-853-8329.
After the meeting, contact:
Matthew Hornbach, Jackson School of Geoscience
The University of Texas Institute for Geophysics, Austin, Texas
Phone: +1-512-636-5030 (cell)
Email: matth@ig.utexas.edu

Christa Stratton | Newswise Science News
Further information:
http://www.geosociety.org
http://www.acsmeetings.org

More articles from Earth Sciences:

nachricht A damming trend
17.12.2018 | Michigan State University

nachricht Live from the ocean research vessel Atlantis
13.12.2018 | National Science Foundation

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Data storage using individual molecules

Researchers from the University of Basel have reported a new method that allows the physical state of just a few atoms or molecules within a network to be controlled. It is based on the spontaneous self-organization of molecules into extensive networks with pores about one nanometer in size. In the journal ‘small’, the physicists reported on their investigations, which could be of particular importance for the development of new storage devices.

Around the world, researchers are attempting to shrink data storage devices to achieve as large a storage capacity in as small a space as possible. In almost...

Im Focus: Data use draining your battery? Tiny device to speed up memory while also saving power

The more objects we make "smart," from watches to entire buildings, the greater the need for these devices to store and retrieve massive amounts of data quickly without consuming too much power.

Millions of new memory cells could be part of a computer chip and provide that speed and energy savings, thanks to the discovery of a previously unobserved...

Im Focus: An energy-efficient way to stay warm: Sew high-tech heating patches to your clothes

Personal patches could reduce energy waste in buildings, Rutgers-led study says

What if, instead of turning up the thermostat, you could warm up with high-tech, flexible patches sewn into your clothes - while significantly reducing your...

Im Focus: Lethal combination: Drug cocktail turns off the juice to cancer cells

A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.

The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...

Im Focus: New Foldable Drone Flies through Narrow Holes in Rescue Missions

A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.

Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

ICTM Conference 2019: Digitization emerges as an engineering trend for turbomachinery construction

12.12.2018 | Event News

New Plastics Economy Investor Forum - Meeting Point for Innovations

10.12.2018 | Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

 
Latest News

Formed to Meet Customers’ Needs – New Laser Beams for Glass Processing

17.12.2018 | Physics and Astronomy

Preserving soil quality in the long term

17.12.2018 | Architecture and Construction

New RNA sequencing strategy provides insight into microbiomes

17.12.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>