Volcano and Earthquake Hazards in the Crater Lake Region, Oregon
Protecting Crater Lake National Park and Surrounding Communities From Volcano Hazards
The National Park Service, local communities, businesses, and citizens can undertake several actions to mitigate the effects of future eruptions at and near Crater Lake. Long-term hazards mitigation includes using information about volcano hazards when making decisions about land use and the siting of critical facilities, housing, and rights-of-way for transportation and utilities. Development can (1) avoid areas judged to have an unacceptably high risk, (2) be planned in such a way as to reduce the level of risk, or (3) include engineering measures to mitigate risk. Limits on development and land use within Crater Lake National Park and the ability of the National Park Service to control access simplify volcanic risk mitigation. In addition, the relatively low probability of lahars originating on Mount Mazama and flowing down the surrounding valleys limits the degree to which communities outside the park need to prepare for such unlikely events. Note that in the Crater Lake region, seismic risk may be as significant as volcanic risk (see Preparing for an earthquake affecting the Crater Lake region).
When volcanoes erupt or threaten to erupt, short-term emergency responses are needed. Such responses will be most effective if citizens and public officials have an understanding of volcano hazards and have planned the actions needed to protect communities. Because the time can be short between onset of precursory activity and an eruption (days to months), and because some hazardous events can occur without any warning, suitable emergency plans should be made beforehand. Public officials need to consider such issues as public education, communications, and evacuation planning. The last deserves special consideration at Crater Lake because of the limited road access to the heavily used south rim of the caldera. Although the number of people located there at any given time is not great, disruption of the road system could make rapid evacuation challenging.
Business owners, school officials, and individuals should also make plans to respond to volcano emergencies. Planning is not only prudent, it is vital. Once an emergency begins, public resources can often be overwhelmed, and citizens may need to provide for themselves and make their own informed decisions. The Red Cross recommends that certain basic items be kept in homes, cars, and businesses in case of emergency, such as portable radios, flashlights, first aid kits, emergency food and water, etc. These items may prove very valuable in a volcano emergency. Two important additional items are (1) knowledge about volcano hazards and (2) an emergency plan of action. If you work or reside within the proximal hazard zone, know how to get safely out of the zone quickly and be aware that hazard zone boundaries are not sharp lines on the ground. Once an eruption begins, the proximal hazard zone can be affected by a pyroclastic surge so rapidly that escape may not be possible. If you are located within a hazard zone for lahars, know how to move safely to high ground rapidly realizing that moving quickly on foot to the highest ground in the vicinity may be the best strategy. A safe height above a river channel depends on several factors: size of the flow, distance from the volcano, and shape of the valley. If you decide to evacuate down valley, realize that these flows can travel as fast as 20 m/s (45 mps). Be sure that you don’t move into a more hazardous area. Be aware that others also may be trying to evacuate at the same time as you are, and escape routes on roads may become dangerously congested. For example, if highway 97 becomes closed for any reason (such as tephra fall), highway 62 can become choked with redirected traffic.
