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Category: Geology (page 2 of 3)

11.30.2012

how old is the grand canyon

Image from yabbedoo travel & tech.

Conventional wisdom has it that the Grand Canyon was carved out by the Colorado some 6-7 million years ago.  Now, new chemical studies of the helium spectra of  Canyon rock are calling that wisdom into question claiming that the canyon is over 60 million years old. From Science News:

But the new study, reported online November 29 in Science, looks instead at the chemistry of rocks exposed throughout the canyon. Rocks get cooler as erosion strips away the material above them. That cooling is chemically preserved in several ways, including in helium within the mineral apatite.

“When the apatite is hot, the helium simply diffuses out of the crystal; when the apatite is cold, helium is completely retained,” says study leader Rebecca Flowers of the University of Colorado Boulder. “So by measuring the helium we are constraining when the rock went from hot to cold as it moved closer to the Earth’s surface, or as the Earth’s surface moved closer to the rock as the canyon was carved.”

Flowers and Kenneth Farley of Caltech looked at helium in apatite crystals throughout the canyon, including how the element was distributed within the crystals — which gives more clues as to whether the rock cooled slowly or quickly. The scientists concluded that some ancient river must have carved out a chasm roughly the shape and size of the Grand Canyon by around 70 million years ago.

Not everyone is convinced by the new findings, which build on earlier work from the same research team. Karl Karlstrom, a geologist at the University of New Mexico, says that there must have been canyons throughout the area 70 million years ago, but most geological evidence supports the modern canyon — what visitors see today when standing at the rim — appearing only in the last 5 million to 6 million years.

Also check the New York Times and Science for more.

11.07.2012

martian dirt similar to hawaiian soil

The view from the top of Mauna Kea in Hawaii.

Curosity has been examining scoop fulls of Martian soil by x-ray diffratcion and its analysis is similar to the soil in parts of Hawaii. For the scientists involved in the project this was not an unexpected result. From Scientific American:

“This Martian soil that we’ve analyzed onMars just this past week appears mineralogically similar to some weathered basaltic materials that we see on Earth,” David Bish, a CheMin co-investigator with Indiana University, told reporters. He cited as an example the “weathered soils on the flanks of Mauna Kea in Hawaii.”

…

CheMin’s first results—obtained using soil Curiosity scooped at a site called “Rocknest”—aren’t terribly surprising, researchers said.

“Much of Mars is covered with dust, and we had an incomplete understanding of its mineralogy,” Bish said in a statement. “We now know it is mineralogically similar to basaltic material, with significant amounts of feldspar, pyroxene and olivine, which was not unexpected. Roughly half the soil is non-crystalline material, such as volcanic glass or products from weathering of the glass.”

 

04.11.2012

global warming is real

This past March was unsually warm in case you didn’t notice. From Sciencenews.org:

People may argue about why Earth is warming, how long its fever will last and whether any of this warrants immediate corrective action. But whether Earth is warming is no longer open to debate. The National Oceanic and Atmospheric Administration has just published domestic examples to reinforce what Americans witnessed last month — either on TV or in their own backyards.

Let’s start with the heat: March 2012 temperatures averaged 10. 6° Celsius (51° Fahrenheit) — or 5.5 °C warmer than the 20th century average across the contiguous United States. Throughout the more than 115 years that national U.S. weather data have been compiled, only one other month (January 2006) surpassed this past March in its departure from the average.

In all, U.S. weather stations logged almost 15,300 all-time highs, last month, roughly half of them for nighttime temps. “There were 21 instances of the nighttime temperatures being as warm, or warmer, than the existing record daytime temperature for a given date,” NOAA’s new analysis finds. Only Alaska bucked the trend; its temperatures were the tenth coolest for March.

 

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