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Wednesday, Apr 17 2013 02:26 PM

How high is Mt. Whitney? Depends on when you ask

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    By ZUMA Press

    Sierra Nevada, Spanish for 'Snowy Range,' is a 400-mile-long mountain range hugging the eastern portion of California. It contains the highest mountain in the lower 48 states, Mount Whitney.

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BY JOHN COX Californian staff writer jcox@bakersfield.com

It won't make hiking to the top any easier, but Mount Whitney may be 5 feet shorter than most people thought.

The highest peak in the contiguous United States may be an even 14,500 ft., according to numbers attributed to the U.S. Geological Survey, based on new estimates of Earth's average sea level.

That would be down from a recently determined 14,505 ft. level.

Whitney's supposed new height was widely disseminated late Tuesday by the Sequoia and Kings Canyon national parks -- and then retracted, sort of.

Mount Whitney, named after a former state geologist, is one of the West Coast's most important geological landmarks and it is a popular destination for hikers and sightseers.

In the mid-19th century, state geologists lugged barometers made of mercury and glass tubes up mountain trails to take air pressure readings.

Then in the early part of the last century, surveyors relied on a network of known elevations to triangulate the altitude of various peaks. More recently, geologists have turned to the satellite-based Global Positioning System.

Geologists have said the new estimate's impact is probably minimal, given that the surrounding area's elevation likely hasn't changed relative to Mount Whitney. But it could force recalibration of official maps, which would affect land surveying work.

If it turns out to be 14,500 ft., that would be at least 60 feet higher than the No. 2 peak, Colorado's Mount Elbert, but well below the nation's high point, 20,320-foot Mount McKinley in Alaska.

Dana Dierkes, public affairs specialist for the two parks, announced the 14,500 ft. figure late Tuesday.

Twenty-four hours later she backed off, saying the latest measurement is still up in the air, so to speak. She said she had publicized what turned out to be an unofficial new height for the summit at the boundary of Tulare and Inyo counties.

"We're in the process of updating our information," Dierkes said. "We're going to go back to 14,494 feet ... But ongoing study and analysis is pending.

"We're so sorry for the confusion."

Apparently Dierkes doesn't use it but only a few years ago, government estimates changed Mount Whitney's estimated altitude from 14,494 feet to 14,505. That was based on a new understanding of the Earth's pear-like shape, called the geoid.

This week's supposed new elevation had been based on new estimates of Earth's average sea level, according to the parks service.

Mount Whitney is actually rising as a result of geologic forces, not falling.

Cal State Bakersfield geology professor Jan Gillespie said there are two theories for why the mountain is slowly getting taller. One is that "mantle drip" beneath Tulare Lake is propping up the surrounding area, including Mount Whitney, even as it gradually lowers the Central Valley.

A more recent theory is that part of the earth's surface broke off from the North American Plate as it was being forced under by the opposing Pacific Plate. Gillespie said this theory holds that the broken section has floated up and is now buoying the North American Plate -- and Mount Whitney along with it.

There may be practical implications of Mount Whitney's apparently fluctuating peak. The National Geodetic Survey, which tracks changes to the Earth's surface caused by things like oil field subsidence, uses mountain peaks and other elevations as benchmarks for the data that it updates and shares with land surveyors.

A Geodetic Survey spokesman said Wednesday that it already lists Whitney at 14,500 ft. but that new data due out in 2022 will likely lower the elevation of the entire area, which could reduce the peak's elevation by three feet.

"Elevations are constantly changing throughout the United States," said Donald Britton, a surveyor with McIntosh & Associates in Bakersfield. He added that any revised estimate would not affect past surveying projects but could change the numbers used in future jobs.

Scientists have their own reasons for monitoring mountaintop elevations. Chris Wills, a supervising engineering geologist with the California Geological Survey, said the agency takes an interest in peak elevations because of what they say about gradual changes in Earth's surface.

"That has implications for both the ancient history of the area and what can happen next: Where are you likely to see rock falls or landslides or floods?" he said.

How long any new estimate will stand is anyone's guess. A technical information specialist at the USGS, Mitch Adelson, said technological advancements will likely continue to refine measurements.

"There are always little changes," he said. "Accuracy things always change a little bit."

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