Download Tsunami Expert - Spokane Public Schools

Project GLAD
Plate Tectonics (6-8)
Expert Group
Tsunami
Interesting Facts
A tsunami is often misnamed a tidal wave, but in fact, a tsunami is not just one
wave but usually a series of seven or eight, that have nothing to do with the tide. In the
open ocean, tsunamis are only about one meter high, but as they approach shallower
waters and the shore, they grow to heights as high as eighty-five meters. The term
tsunami comes from the Japanese, meaning "harbor" (tsu, 津) and "wave" (nami, 波).
Definition & Causes of a Tsunami
The most common causes of tsunamis are volcanoes, earthquakes and earth slides
- mostly undersea. Volcanoe magma chambers collapses forming a crater sometimes up
to one kilometer in diameter. Water gushes into this crater in a very short amount of time,
causing a tsunami. Earthquake originated tsunamis occur when the Earth's crust on either
side of a fault jolt past each other, with a kind of vertical movement, displacing huge
amounts of water, causing waves. Tsunamis can also be caused by land sliding in to the
sea with such great force that it creates a wave, similar to the effect of throwing a pebble
into a puddle of water.
Location of Tsunamis
About 80% of tsunamis occur in the Pacific Ocean, but are possible wherever
there are large bodies of water, including lakes. Tsunamis usually only occur in coastal
regions; islands are the main targets. The Pacific Ocean is surrounded by the Ring of
Fire, a highly active volcano and earthquake zone.
Effects on Civilization
"Imagine a flood of water swirling up the street, lifting cars and flinging them
through flimsy buildings as it goes. Then imagine the buildings themselves being washed
away, leaving behind little more than scattered rubble. This is a tsunami.” ( Natural
Disasters, Readers Digest, 1996.) The effects of a Tsunami on any region vary, depend on its
magnitude, the distance of the region from the epicenter, the local geology (physical
features), and the type of construction in the region. The deadliest tsunami in history
occurred on December 26, 2004. The tsunami left around 1,126,900 people homeless
and killed more than 283, 000 people in India, and surrounding countries. Tsunami
waves destroy cities, leaving unfit water to drink causing disease. An Indian village
suffered only minimal damage and few deaths because the wave broke against a forest of
80,244 trees planted along the shoreline in 2002 in a bid to enter the Guinness Book of
Records.
Geological Effects
The geologic changes related to Tsunamis are the changes in the ocean floor due
to volcanic and earthquake activities or landslides. The actual waves have not been
recorded to have changed the geologic structure of the coastlines and islands that are
affected.