Tsunamis

open ocean waves caused by:

Tsunamis are not tidal waves.(The tides are caused mainly by the moon’s gravity and are not related to tsunamis).

Indonesia tsunami(2004) caused bya M 9.0 quake along a subductionzone

(a 750-milesection of the fault moved 50 feet!)

on the open ocean:

• tsunamis have wave heights of 3 ft and wavelengths of 60 miles

• Speed: +500 mph

http://www.noaanews.noaa.gov/stories2005/s2365.htm

World propagation of tsunami:

The height and the distance inland that tsunamis travel depends on the topography and the shape of coastline.

globalsecurity.org

Tsunami warning Sign: in some cases, tsunamis are preceded by a fall in sea level

Before

After

Before andafter tsunamisatelliteimages of Indonesiancoastline

Survivorstories

Most people that died in the Asian tsunami drownedor were killed by floating debris. However, afterthe immediate disaster other hazards became apparent:

Since there may be severalminutes between waves,survivor are often sweptback out to sea

Tsunami relief efforts:

• relief aid for the tsunami victims came from all parts of the world

• former US Presidents Bush and Clinton are in charge of United Nations joint tsunami reliefeffort

Some problems with providing relief aid:

Tsunami warning systems are composed of 3types of devices:

Pacific Ocean Tsunami warning system

Deep OceanTsunameter:

• uses a

on thebottom of the ocean todetect passingtsunami waves

http://www.usgs.gov/hazards/tsunamis/

http://ioc3.unesco.org/indotsunami/

Indian Ocean tsunami warning system:

USGS tsunami hazard page:

The highestrisk area for tsunamisin the US is along the west coast

Tsunami deposits (sand)along the west coast of US

Hawaiian Islands are volcanic. As these volcanoescool they become weak and are subject to ‘flank collapse’.When geologists first mapped the ocean floor around Hawaiithey found evidence for these collapses.

Steven Earle, 2004. Malaspina University-College, Geology Department

Steven Earle, 2004. Malaspina University-College, Geology Department

Last known collapse:110,000 years ago

• A tsunami generated in this way today would devastate coastal areasaround the Pacific.

The Canary Islands are volcanic islands similar to Hawaii.Island flank collapse would threaten coastal areas around the Atlantic, including cities along US East Coast.

The last knownflank collapsein Canary Islands:

Earth Sciences, Ga. Tech

Estimated tsunami travel time from Canary Islands to New York: