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Beryllium 10 cosmogenic dating places massive Zion valley floor landslide and resulting lake to 4800 years ago

© 2016 Peter Free

Citation — to study

Jessica J. Castleton, Jeffrey R. Moore, Jordan Aaron, Marcus Christl, and Susan Ivy-Ochs, Dynamics and legacy of 4.8 ka rock avalanche that dammed Zion Canyon, Utah, USA, Geological Society of America 26(6): 4-9, DOI: 10.1130/GSATG269A.1 (June 2016)

Citation — to press release

Lee Siegel, How a Huge Landslide Shaped Zion National Park, University of Utah (26 May 2016) (with photographs and simulation graphics)

Cool catastrophes?

What follows will mean more to people who have been to Zion National Park in the United States.

From the University of Utah:

A Utah mountainside collapsed 4,800 years ago in a gargantuan landslide known as a “rock avalanche,” creating the flat floor of what is now Zion National Park by damming the Virgin River to create a lake that existed for 700 years.

Computer simulations matched known landslide deposits and show the huge slide rushed southeast across Zion Canyon in about 20 seconds, with an average speed of 112 mph and a peak speed of 180 to 200 mph.

“It was certainly moving more than 150 mph when the huge wall and peak crashed down,” [Jeffrey] Moore says. Then, for 30 more seconds, the slide debris spread up and down Zion Canyon. “By a minute it was pretty much done.”

“The original deposit was 2 miles long and just under a mile wide,” with a maximum thickness of 650 feet and average thickness of 310 feet, he says, adding the landslide’s lower end is at the road junction “right at the mouth of Zion Canyon.”

“We have conducted a rigorous and complete analysis of this landslide for the first time,” Moore says. The study concluded the landslide most likely happened 4,800 years ago as single event, with a range of uncertainty so that it could have happened as early as 5,200 years ago or as recently as 4,400 years ago.

The method exploits the fact that after a landslide, boulders atop the slide have surfaces exposed to the sky for the first time. Particles from incoming cosmic rays begin to hit the boulder surfaces, creating beryllium-10. The longer a boulder is exposed, the greater the amount of beryllium-10, allowing scientists to determine when the boulder’s surface first was exposed by the landslide.

With permission from the National Park Service, Moore and colleagues sampled 12 boulders from the landslide’s surface, crushed the notebook-sized rock samples and analyzed their beryllium-10 content.

© 2016 Lee Siegel, How a Huge Landslide Shaped Zion National Park, University of Utah (26 May 2016) (extracts)

Lee Siegel’s excellent press release contains photographs and graphics.

The same message in scientific language

From the abstract:

The Sentinel rock avalanche blocked the mouth of Zion Canyon, Utah, USA, over a distance of 3.3 km and created a large lake that filled the canyon floor with sediment, transforming this iconic desert landscape.

Reconstructing topography before and after the failure, we calculate an original deposit volume of 286 million m3 with maximum thickness of 200 m. New cosmogenic nuclide surface exposure ages of 12 boulders from across the deposit reveal a mean age of 4.8 ± 0.4 ka and are consistent with single-event emplacement.

Results of 3D numerical runout simulations agree well with mapped deposit boundaries and thickness, affirming our hypothesized failure scenario and indicating an average runout velocity of 50 m/s.

Following partial breach of the landslide dam, we estimate that water levels stabilized for ~700 yr until the lake filled with sediment. Deposited lacustrine clays reveal a period when Zion Canyon was filled by the 3 km2 Sentinel Lake extending more than 7 km upstream.

© 2016 Jessica J. Castleton, Jeffrey R. Moore, Jordan Aaron, Marcus Christl, and Susan Ivy-Ochs, Dynamics and legacy of 4.8 ka rock avalanche that dammed Zion Canyon, Utah, USA, Geological Society of America 26(6): 4-9, DOI: 10.1130/GSATG269A.1 (June 2016) (at Abstract) (extracts)

The moral? — Understanding pertinent geology makes travel more interesting

Appreciation to Lee Siegel and the University of Utah for their visually informative overview.

Small British study shows physician reluctance — to implement other than face to face patient interactions — demonstrating the gap between hype and reality

© 2016 Peter Free

Citation — to study

Heather Brant, Helen Atherton, Sue Ziebland, Brian McKinstry, John L Campbell, and Chris Salisbury, Using alternatives to face-to-face consultations: a survey of prevalence and attitudes in general practice, British Journal of General Practice, DOI: 10.3399/bjgp16X685597 (online first, 24 May 2016)

The gist — “Ya gotta come in”

From the abstract:

Despite considerable rhetoric about the need for general practices to offer alternatives to face-to-face consultations, such as telephone, email, and internet video consultations, the extent to which such technologies are actually used at present is unclear.

A postal questionnaire survey was sent to each of the GPs and practice managers of 421 practices between January and May 2015.

A response was received from 319/421 practices (76%).

Although the majority of the practices reported that they were conducting telephone consultations frequently (n = 211/318, 66%), fewer were implementing email consultations (n = 18/318, 6%), and most (n = 169/318, 53%) had no plans to introduce this.

None were currently using internet video, and 86% (n = 273/318) had no plans to introduce internet video consultations.

Despite policy pressure to introduce consultations by email and internet video, there is a general reluctance among GPs to implement alternatives to face-to-face consultations.

 

This identifies a substantial gap between rhetoric and reality in terms of the likelihood of certain alternatives (email, video) changing practice in the near future.

© 2016 Heather Brant, Helen Atherton, Sue Ziebland, Brian McKinstry, John L Campbell, and Chris Salisbury, Using alternatives to face-to-face consultations: a survey of prevalence and attitudes in general practice, British Journal of General Practice, DOI: 10.3399/bjgp16X685597 (online first, 24 May 2016) (extracts)

The moral? — Inertia is in charge

I recently had to drive for 90 minutes just to have a nurse check surgical site healing. Something that I could have much more easily done via an already installed video and medical communications link from my primary care manager’s office.

The technology is here. Just not the will to use it. When money keeps flowing in, why change?

Surgeons apparently differ wildly regarding the wisdom of doing surgery for identical routine conditions — says a possibly indicative UCLA study

© 2016 Peter Free

Citation — to study

Greg D. Sacks, Aaron J. Dawes, Susan L. Ettner, Robert H. Brook, Craig R. Fox, Marcia M. Russell, Clifford Y. Ko, and Melinda Maggard-Gibbons, Impact of a Risk Calculator on Risk Perception and Surgical Decision Making: A Randomized Trial, Annals of Surgery, DOI: 10.1097/SLA.0000000000001750 (published ahead of print, 19 May 2016)

Citation — to press release

University of California – Los Angeles Health Sciences, To operate or not to operate: Serious question with no clear answers, ScienceDaily (20 May 2016)

An invitation to confusion

From the press release:

In the first study, the researchers found that surgeons differ in their recommendations for surgery largely because they differ in how they perceive the risks and benefits of operating versus not operating. The surgeons’ estimates of these risks and benefits varied widely. When assessing outcomes such as the likelihood that a patient would suffer a serious complication, for instance, one surgeon could perceive zero risk for a given procedure while another would see a 100 percent chance of that same procedure leading to a major complication.

For the second study, the same team of researchers examined how the use of a surgical risk calculator would influence surgeons’ decision to pick up a scalpel under the same set of hypothetical circumstances.

The online risk calculator, developed by the American College of Surgeons National Surgical Quality Improvement Program, uses national registry data to gauge the chances of postoperative complications based on type of surgery, patient demographics, and the state of a patient’s health.

While the calculator led surgeons to make more accurate predictions on average and resulted in less variance in their judgements, there was no change in a surgeon’s likelihood of recommending an operation.

The take-home message of both studies is that there may not always be clear answers on the best treatment. For that reason, patients might benefit from getting involved in the decision-making process, Sacks said.

“In areas of such uncertainty, these studies suggest that the best we can do is estimate the risks and benefits of each possible treatment and then work with the patient to find a treatment that matches his or her preferences and values,” he said.

© 2016 University of California – Los Angeles Health Sciences, To operate or not to operate: Serious question with no clear answers, ScienceDaily (20 May 2016) (extracts)

The numbers

From the abstract:

We asked a national sample of surgeons to assess the risks (probability of serious complications or death) and benefits (recovery) of operative and nonoperative management and to rate their likelihood of recommending an operation (5-point scale) for 4 detailed clinical vignettes wherein the best treatment strategy was uncertain

Surgeons were randomized to the clinical vignettes alone (control group; n = 384) or supplemented by data from a risk calculator (risk calculator group; n = 395). We compared surgeons’ judgments and decisions between the groups.

Surgeons exposed to the risk calculator judged levels of operative risk that more closely approximated the risk calculator value (RCV) compared with surgeons in the control group

mesenteric ischemia: 43.7% vs 64.6% . . . (RCV = 25%)

gastrointestinal bleed: 47.7% vs 53.4% . . . (RCV = 38%)
small bowel obstruction: 13.6% vs 17.5% . . . (RCV = 14%);
appendicitis: 13.4% vs 24.4% . . . (RCV = 5%)].

Surgeons exposed to the risk calculator also varied less in their assessment of operative risk

(standard deviations:

mesenteric ischemia 20.2% vs 23.2% . . .

gastrointestinal bleed 17.4% vs 24.1% . . .

small bowel obstruction 10.6% vs 14.9% . . .

appendicitis 15.2% vs 21.8% . . .

However, averaged across the 4 vignettes, the 2 groups did not differ in their reported likelihood of recommending an operation . . . .

Exposure to risk calculator data leads to less varied and more accurate judgments of operative risk among surgeons, and thus may help inform discussions of treatment options between surgeons and patients. Interestingly, it did not alter their reported likelihood of recommending an operation.

© 2016 Greg D. Sacks, Aaron J. Dawes, Susan L. Ettner, Robert H. Brook, Craig R. Fox, Marcia M. Russell, Clifford Y. Ko, and Melinda Maggard-Gibbons, Impact of a Risk Calculator on Risk Perception and Surgical Decision Making: A Randomized Trial, Annals of Surgery, DOI: 10.1097/SLA.0000000000001750 (published ahead of print, 19 May 2016)  (at Abstract) (paragraph split)

The moral? — Irrationality rules?

Notice the surgeons’ sizable departures from the risk calculator.
And even after using the calculator to improve their sense of the risk considerations, the sample group apparently did not alter their surgical recommendations.

I doubt that patient discussion will much improve the situation. Most patients are not knowledgeable enough to have workable intuitions regarding the elements being considered.