Road Construction Delays on Park Roads for 2014 Season
Expect occasional 15-minute to 1-hour delays in Sequoia and Kings Canyon National Parks on weekdays only (times vary), including delays to/from the General Sherman Tree, Crystal Cave, and Grant Grove. More »
Vehicle Length Limits in Sequoia National Park (if Entering/Exiting Hwy 198)
Planning to see the "Big Trees" in Sequoia National Park? If you enter/exit via Hwy. 198, and your vehicle is longer than 22 feet (combined length), please pay close attention to vehicle length advisories for your safety and the safety of others. More »
You May Have Trouble Calling Us
We are experiencing technical problems receiving incoming phone calls. We apologize for the inconvenience. Please send us an email to SEKI_Interpretation@nps.gov or check the "More" link for trip-planning information. More »
Air Quality -- Ozone
Good and Bad Ozone
Ozone is made of three joined oxygen atoms, and it is found both in the Earth's upper atmosphere and at ground level. Ozone can be helpful or harmful, depending on where it is found:
Good ozone occurs naturally in the Earth's upper atmosphere (stratosphere)- 10 to 30 miles above the Earth's surface - where it shields us from harmful ultraviolet rays.
Bad ozone forms near the ground (lower troposphere) when pollutants from cars, power plants, and other sources react chemically. Sunlight provides the energy that drives this chemical reaction, so the amount of ozone in the atmosphere is highest on summer afternoons.
Ozone may be the most damaging pollutant here. Individual ponderosa and Jeffrey pine trees that are ozone-sensitive show extensive injury to their foliage at present ozone levels. For example, one study found that nearly 90% of Jeffrey pines in or near the Giant Forest showed visible signs of ozone injury. Compared to ozone-resistant individuals, ozone-sensitive pines have lower photosynthetic rates, lose their needles earlier, and have diminished annual ring growth. In contrast to pines, mature giant sequoias seem to be relatively resistant to present ozone levels. However, newly emerged sequoia seedlings are suspected to be more vulnerable to ozone injury.
We humans are very vulnerable to ozone damage too. It can irritate the human respiratory system causing coughing, irritation in the throat, and/or an uncomfortable sensation in the chest. The elderly and those with pre-existing respiratory problems (e.g. asthma, bronchitis) are more vulnerable to these effects.
For further information, visit the Environmental Protection Agency AirNow Web Site.
Did You Know?
The park newspaper (The Guide) comes out five times a year. It covers Sequoia & Kings Canyon National Parks, and the Hume Lake area of Sequoia National Forest and Giant Sequoia National Monument. Planning a trip? See the most recent issue for the season you expect to be here and see what to expect. More...