Page 541 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Chapter 16 Oceans, Coastal Systems, and Wind Processes 505
Numbers indicate hours after the initial event
Tsunami Warning and Mitigation System was created as part of the ongoing United Nations tsunami-warning- system project (see itic.ioc-unesco.org/). This event also prompted the addition of 32 ocean stations (pressure sen- sors on the ocean floor with accompanying surface buoys) as part of the Deep-Ocean Assessment and Reporting of Tsunamis (DART), a global tsunami warning system de- veloped by NOAA in the United States. (For NOAA’s tsu- nami research program, see nctr.pmel.noaa.gov/.)
The 2011 Tohoku earthquake in Japan (discussed in Focus Study 13.2) triggered a tsunami that killed over 15000 people. Despite warning systems in what is one of the most technologically advanced countries in the world, there was little time for evacuation. Focus Study 16.2 describes the tsunami and its effects through the Pacific Ocean basin. Revisit the photos in Focus Study 13.2 to see tsunami-related damage in Japan and the wave as it moved inland.
Warning centres throughout the world use the DART network of 39 stations in the Pacific, Indian, and Atlantic Oceans, discussed in Focus Study 16.2. When a tsunami triggers the DART sensors, regional warning centres issue bulletins to regions that are likely to be affected. The effectiveness of these warnings varies; for those closest to the undersea
disturbance, even the most accurate warning cannot help when there are only minutes to reach safety. See the website of Emergency Management BC for infor- mation about tsunami warnings and preparedness on the Pacific coast of Canada (embc.gov.bc.ca/em/hazard_ preparedness/tsunami_preparedness_information.html).
Coastal System Outputs
Coastlines are active, energetic places, with sediment being continuously delivered and removed. The action of tides, currents, wind, waves, and changing sea level pro- duces a variety of erosional and depositional landforms. We look first at erosional coastlines, where in general more sediment is removed than is deposited. We then look at depositional coastlines, where in general more sediment is deposited, primarily from streams, than eroded. In this era of rising sea level, coastlines are be- coming even more dynamic.
Coastal Erosion
The active margin of the Pacific Ocean along North and South America is a typical erosional coastline. Ero- sional coastlines tend to be rugged, of high relief, and
INDIA
SRI Epicentre LANKA
Sumatra
I N D O N E S I A
AUSTRALIA
CHINA
◀Figure 16.12 Travel times for the 2004 indian Ocean tsunami. Black circle indicates the earth- quake epicentre located 250 km off the west coast of northern Sumatra, indonesia. Map compiled with in- tegrated data from several sources. [nOaa.]