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Roadblocks and speed limits: Geoscientists study Alaska’s Denali fault

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Roadblocks and speed limits: Geoscientists study Alaska’s Denali fault


Utah State University geochemist Dennis Newell collects data from a spring along the Cantwell segment of Alaska’s Denali Fault. He and colleagues published findings in the Geology, citing evidence of mantle-to-crust connections that increase the possibility of a future major earthquake. Credit: Jeff Benowitz

The 1,200-mile-long Denali Fault stretches in an upward arc from southwestern Alaska and the Bering Sea eastward to western Canada’s Yukon Territory and British Columbia. The long-lived and active strike-slip fault system, which slices through Denali National Park and Preserve, is responsible for the formation of the Alaska Range.

“It’s a big, sweeping fault and the source of a magnitude 7.9 earthquake in 2002, that ruptured more than 200 miles of the Denali Fault, along with the Totschunda Fault to the east, causing significant damage to remote villages and central Alaska’s infrastructure,” says Utah State University geochemist Dennis Newell.

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Understanding the restless fault’s mantle-to-crust connections provides critical information for understanding the lithospheric-scale fault’s seismic cycle, says Newell, associate professor in USU’s Department of Geosciences.

He and colleagues Jeff Benowitz, an Alaska-based geochronologist, Sean Regan of the University of Alaska Fairbanks, and doctoral candidate Coleman Hiett of USU, collected and analyzed helium and carbon isotopic data from springs along a nearly 250-mile segment of the fault and published their findings, “Roadblocks and Speed Limits: Mantle-to-Surface Volatile Flux in the Lithospheric Scale Denali Fault, Alaska,” in Geology.

“Active strike-slip faults like Denali have three-dimensional geometries with possible deep conduit connections below the Earth’s surface,” Newell says. “But we don’t know much about how and if these connections are maintained.”

To examine these possible deep connections, Newell and Regan sampled 12 springs along the Denali and Totschunda Faults, by way of helicopter and on foot, to the remote, mountainous regions of Alaska’s interior.

“Helium-3, a rare isotope of helium gas, in springs is a good indicator of whether or not an area has a connection to the Earth’s mantle,” Newell says. “Warm, bubbling springs west of the 2002 earthquake rupture, along the Cantwell segment of the Denali Fault, have a strong helium-3 signature, indicating intact connections to the mantle. In contrast, springs along the ruptured fault segment only have atmospheric gases, suggesting a ‘roadblock’ preventing the flow of mantle helium to the surface.”

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These observations, he says, have implications for how groundwater pathways along the fault are changed by earthquakes, and the timescales on which they heal.

“The last major earthquake on the Cantwell segment was 400 years ago, and the helium data suggest those mantel connections have been reestablished,” Newell says. “These bubbling springs are indicative of the possibility of a future large destructive earthquake along the Denali Fault segment near Denali National Park, which receives some 600,000 visitors each summer.”

The geoscientists also seek data on how fast helium can move from the mantle to the crust along active faults.

“That’s the ‘speed limit’ part of our research,” Newell says. “This is important as it reveals mantle-to-surface volatile flux and how fluid pressure gradients may impact fault strength and seismicity along the fault.”

The fault’s mantle fluid flow rates fall in the range observed for the world’s other major and active strike-slip faults that form plate boundaries, he says, including California’s San Andreas Fault and Turkey’s North Anatolian Fault Zone. These types of faults host large, devastating earthquakes, such as February 2023’s deadly earthquake on the East Anatolia Fault, which caused widespread destruction in Turkey and Syria.

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“Quantifying crust-to-mantle connections along major strike-slip faults is critical for understanding linkages between deep fluid flow, seismicity and fault healing,” Newell says.

More information:
Dennis L. Newell et al, Roadblocks and speed limits: Mantle-to-surface volatile flux through the lithospheric-scale Denali fault, Alaska, Geology (2023). DOI: 10.1130/G51068.1

Provided by
Utah State University

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Citation:
Roadblocks and speed limits: Geoscientists study Alaska’s Denali fault (2023, June 6)
retrieved 6 June 2023
from https://phys.org/news/2023-06-roadblocks-limits-geoscientists-alaska-denali.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
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Alaska

North to Alaska: Sirowich transferring to Anchorage

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North to Alaska: Sirowich transferring to Anchorage


Kenzie Sirowich was looking for a new opportunity. The former standout for the Seymour High girls basketball team wanted more for herself after two years if playing basketball and studying health sciences at Franklin Pierce University in Rindge, N.H.

Sirowich found her opportunity nearly 4,500 mi



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Alaska's Pristine Waterways Are Turning a Shocking Orange

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Alaska's Pristine Waterways Are Turning a Shocking Orange


Some of Alaska’s clear, icy blue waterways are turning a startling rust orange – so intense it’s visible from Earth’s orbit.

“The stained rivers are so big we can see them from space,” says University of California (UC) Davis environmental toxicologist Brett Poulin. “These have to be stained a lot to pick them up from space.”

After first noticing the problem in 2018 from river banks and fly-overs, National Park Service ecologist Jon O’Donnell, Poulin and their colleagues used satellite imagery and public reports to identify over 75 remote streams recently tainted this unusual orange color, across almost 1,000 kilometers (1,610 miles) of Alaska’s Brooks Range.

“There are certain sites that look almost like a milky orange juice,” describes O’Donnell. “Those orange streams can be problematic both in terms of being toxic but might also prevent migration of fish to spawning areas.”

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Samples from some of these waterways collected between June and September 2022 contained high concentrations of iron and other toxic metals, including zinc, copper, nickel, and lead, when compared to nearby healthy streams. In some cases, these pollutants ramped up the water’s acidity from the usual pH of 8 to 2.3.

An aerial view of the rust-colored Kutuk River in Gates of the Arctic National Park in Alaska. (Ken Hill/National Park Service)

The results look similar to acidic mining runoff, Poulin says, yet there are no mines anywhere near these locations.

Instead, by examining satellite imagery from 1985 to 2022, O’Donnell, Poulin and their colleagues determined this strange phenomenon has only been occurring during the last decade, and it coincides with warmer weather and increased snowfall.

“Our working hypothesis is that the thawing of permafrost soil is allowing water to infiltrate deeper and interact with minerals that have been locked away for thousands of years,” explains Poulin.

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The Arctic is warming about four times faster than the rest of our planet. That extra heat melts frozen ground, increases microbial activity, and causes ‘shrubification’ – with those new roots further disturbing the soil. Together these processes are exposing the previously protected minerals to weathering and displacing them into watersheds.

Climate change and associated permafrost thaw appear to be the primary drivers of stream impairment,” the researchers conclude. “Stream discoloration was associated with dramatic declines in macroinvertebrate diversity and fish abundance.”

This change in water chemistry due to acid rock drainage threatens not only wildlife but local people who rely on these streams for drinking water and subsistence fishing.

O’Donnell and the team are continuing their investigation in the hopes of understanding the broader ecological impacts for the region and working out when and where the toxic orange taint will strike again.

“There’s a lot of implications,” explains O’Donnell. “As the climate continues to warm, we would expect permafrost to continue to thaw and so wherever there are these types of minerals, there’s potential for streams to be turning orange and becoming degraded in terms of water quality.”

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Their research was published in Communications Earth & Environment.



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FAA reauthorization bill addresses aviation issues important to Alaska

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FAA reauthorization bill addresses aviation issues  important to Alaska


The business of rulemaking does not come up often with travelers. That is, until something goes wrong.

Lately, there’s been lots of attention on companies like Boeing, especially since the panel blew off an Alaska Airlines jet after taking off in Portland. Investigations by the Federal Aviation Administration (FAA), the Department of Transportation (DOT), and the U.S. Department of Justice focus on rules and Boeing’s safety procedures designed to keep travelers safe.

For a long time, though, air carriers in Alaska have struggled with aviation rules designed around safety. Some of these rules are better suited for jet carriers flying between big airports. By contrast, Alaska’s aviation infrastructure is scattered across more than 100 airports, serving communities that are off the road system. For these communities, having reliable aviation service is crucial. Many of the rules address how aviators fly in bad weather.

One of the biggest aviation rule-making events is the FAA reauthorization bill, which is mandated every five years. There are specific statutes in the bill that should help Alaska communities and the air carriers that fly there.

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The big parts of the bill include a mandate to the FAA to hire and train more air traffic controllers to fill up to 3,000 vacancies.

Another important part of the bill backs up recent DOT rules which mandate airlines must automatically refund tickets in cash instead of vouchers.

Other parts of the FAA bill are important for Alaskans, particularly those living off the road system in remote communities.

“The new bill addresses basic, fundamental issues that need to get fixed,” said Colleen Mondor, an Alaska aviation author and journalist.

The new bill includes dedicated funding for the installation and upkeep of weather monitoring systems to give pilots the “certified weather” they need to fly under instrument flight rules or IFR. Using IFR approaches, pilots generally can operate with lower minimums than visual flight rules (VFR).

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“The (FAA) bill requires systematic improvements to the upgrade and maintenance of weather observing systems owned by both the FAA and the National Weather Service that experience frequent service outages, disrupting aviation operations throughout our state,” according to a statement from U.S. Sen. Dan Sullivan’s office. Sullivan was instrumental in adding Alaska-centric provisions in the bill.

“The automated weather observation system (AWOS) is a $100,000 piece of equipment that measures fog, wind, snow, pressure and temperature,” said Mondor. “It’s updated every few minutes.”

The quest for better aviation safety in Alaska goes back decades. The effort always gets renewed attention after there’s a fatal crash or an accident.

“We absolutely support it,” said Rob Kelley, head of Grant Aviation, referring to the push for better weather aids and instrument flight rules.

Grant Aviation flies to dozens of communities in Western Alaska on small planes. “We’ve got a lot of money tied up in IFR avionics,” said Kelley. “But we can’t use IFR because the weather reporting system is broken.”

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Grant’s routes include dozens of daily flights in the Yukon-Kuskokwim Delta region. “The weather there is consistently marginal. So we can’t fly there. But we could fly on IFR,” said Kelley.

The National Transportation Safety Board (NTSB) investigates every aviation accident. Since the 1990s, the NTSB has recommended air carriers to fly under IFR regulations.

“Since Jan 1, 1990 there have been 385 fatalities & 231 serious injuries in accidents involving Part 135 operators in Alaska,” wrote Mondor on X. “The cost has been high and it has been paid in blood. Alaska deserves what the Lower 48 has enjoyed for so long and I hope it finally happens.”

Part 135 refers to commuter carriers limited to nine passengers on a single flight. Part 135 carriers are the crucial “last mile” for Alaskans who live off the road system and are dependent on reliable air service more than urban dwellers. Often, Bush Alaskans depend on Part 135 carriers to go to work, to school or to the doctor. Further, these small air carriers provide a vital link by delivering mail and freight.

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Two federal programs, by-pass mail and essential air service, subsidize air carriers to provide better, more affordable service to Alaska’s rural residents.

The new FAA bill “strengthens the Essential Air Service (EAS) program and triples its funding to ensure small and rural communities remain connected to the national airspace system. The EAS program benefits approximately 60 communities in Alaska,” according to Sen. Sullivan’s office.

The DOT rules and new FAA statutes can make for some tedious reading. But these new rules, when applied, can save lives. The new weather monitoring system by itself will not solve all the issues. There are many more components in the quest for better aviation safety in Alaska. But this latest round with the FAA reauthorization covers some crucial steps.





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