Vulkanen Alaska: Activiteit bij Cleveland, Kanaga, Iliamna en meer

quote:

Onrustige vulkaan Alaska bedreigt vliegverkeer

ANCHORAGE - Piloten op vliegroutes tussen Azië en Noord-Amerika moeten extra waakzaam zijn voor een uitbarsting van een vulkaan in Alaska. De Cleveland-vulkaan op de Aleoeten, een eilandengroep tussen de VS en Rusland, lijkt zich op te maken voor de grootste uitbarsting in tien jaar tijd. Dat stellen Amerikaanse seismologen op basis van satellietbeelden, zo meldt persbureau Reuters.

De Cleveland-vulkaan ligt op het eiland Chuginadak, in een afgelegen gebied waar geen seismologische apparatuur aanwezig is. Vulkaanuitbarstingen of naderende uitbarstingen kunnen alleen worden opgemerkt vanuit de ruimte, op basis van satellietfoto's, observaties van piloten of door marinepersoneel dat in de buurt is.

Door het ontbreken van accurate meetapparatuur is het mogelijk dat overvliegende piloten opeens worden verrast door as dat meer dan acht kilometer de lucht in wordt geblazen.

Cleveland staat te boeken als een van de meest bedreigende vulkanen voor de luchtvaart.

quote:

Alert status of Mt Cleveland raised again

Signs of lava at Mount Cleveland prompted volcanologists to raise their alert level Tuesday afternoon for the Aleutian Islands volcano.

The Alaska Volcano Observatory reports "heightened or escalated unrest" and the possibility of an eruption at the 5,676-foot volcano, according to the observatory's website.

Cleveland Volcano comprises the western half of Chuginidak Island, which sits about 115 miles west of Dutch Harbor and 950 miles southwest of Anchorage.
Click here to find out more!

Satellite data and visual observations in late July revealed a lava dome about 140 feet in diameter growing in the volcano's crater, said volcanologist Chris Waythomas. The dome grew another 10 feet or so between Tuesday and Wednesday, according to the observatory.

"Sometimes lava domes like that can be explosive and lead to ash production," Waythomas said.

The volcano observatory raised the advisory status from "advisory" to "watch" and the aviation warning level from yellow to orange.

Cleveland is capable of blasting volcanic ash more than 20,000 feet into the sky -- a significant danger to air traffic in the vicinity -- so staff at the observatory decided to warn aviators of a possible explosive eruption, the researcher said.

Still, it's not certain that any ash-producing eruption will occur, Waythomas said.

quote:

Cleveland may be preparing for a more explosive event
ANCHORAGE, Alaska — A volcano that has been erupting for several days in Alaska's Aleutian Islands may be preparing for a more explosive event, scientists said Wednesday.

Cleveland Volcano, a 5,676-foot peak located on Chuginadak Island, about 940 miles southwest of Anchorage, has been in low-level eruption since the end of July, the Alaska Volcano Observatory said.

"An eruption for us is any time that magma is coming up from the surface in the ground," said John Power, scientist in charge at the observatory, a joint federal-state operation. "This is very much happening here."

Chuginadak Island is uninhabited and the volcano has not posed an immediate hazard to anyone — nor has it affected air traffic, even though it lies directly in the North America-to-Asia flight corridor used by major airlines, Power said.

But there is a possibility that the extrusion of lava is a precursor to a big explosive event that would send ash into the atmosphere, he said.

The dome, if it continues to grow, could plug up the crater, creating pressure that could result in "a fairly sizable explosion that could throw ash up to flight levels," Power said.

The Alaska Volcano Observatory first reported the eruption a week ago, when satellite images showed that the lava dome on the volcano's summit was widening.

Cleveland Volcano covers about half of Chuginadak Island. The closest community to the volcano is Nikolski, an Aleut village of about 20 people located 45 miles to the east.

The fishing port of Unalaska/Dutch Harbor is about 150 miles to the east of the volcano.

Cleveland's last major eruption was in 2001, but it has had several smaller or suspected ash-spewing eruptions since then.

The extrusion of lava into a bigger summit dome is not typical for this volcano, Power said. "This is something we really haven't observed at Cleveland before," he said. However, dome-building events have preceded big explosive eruptions at other Alaska volcanoes, including Redoubt Volcano near Anchorage, he said.

Redoubt's 2009 eruptions caused numerous flight cancellations, as well as a disruption of offshore oil production in nearly Cook Inlet.

quote:

Cleveland Volcano May Disrupt U.S. - Asia Flights as Explosive Event Expected

Several thermal anomalies were observed in satellite views of Alaska's Cleveland volcano over the past 24 hours, but the Alaska Volcano Observatory said Sunday it had received no additional information or observations about activity.

Cleveland currently has an Orange Alert Status which means "explosive eruption is possible within a few days and may occur with little or no warning. Ash plume(s) are not expected to reach 25,000 feet above sea level." AVO predicts "increased numbers of local earthquakes" and "extrusion of a lava dome or lava flows (non-explosive eruption)."

Without a real-time seismic network on the volcano, AVO says it cannot track local volcano-related earthquake activity, provide forecasts of eruptive activity, or confirm explosive or ash-producing events. The observatory is monitoring the volcano using satellite data as it becomes available.

Scientists monitoring the volcano are expecting a more explosive event and have predicted a potential threat on the U.S. - Asia flight corridor used by major airlines, according to The Weather Space.

Mount Cleveland is a stratovolcano that comprises the entire western half of Chuginadak Island, 40 km west of Umnak. Although it is the tallest member of the Four Mountains group, Cleveland is reported to lose snow more rapidly than its neighboring peaks presumably from anomalous heat generation. Hot springs were noted at the base of a volcano on Chuginadak in the 1800s.

Like many other Aleutian volcanoes, the lower flanks of Mount Cleveland, up to about 300 meters elevation, are more irregular and dissected than the upper flanks. The cones on the eastern half of Chuginadak Island are dissected by broad valleys presumably eroded in part by glaciers; in contrast, the upper cone of Mount Cleveland is virtually undissected.

quote:

Alaska Volcano: Eruption Alert Raised at Cleveland Volcano

The Alaska Vulcano that has been erupting since last month is currently being monitored as it continuously build up a lava leak on the flanks of the volcano, increasing the possibility of an eruption, according to AP.

On Tuesday, the Alaska Volcano Observatory raised the volcano’s alert level to watch status.

According to John Power, scientist in charge at the Alaska Volcano Observatory, if the dome continues to grow it could close the crater, creating pressure that could result in "a fairly sizable explosion that could throw ash up to flight levels."

quote:

Cleveland lava dome continues to grow
CHUGINADAK ISLAND, ALASKA-Mount Cleveland, a strato-volcano perched on Chuginadak island, has had its Volcano Alert status raised back up to "Watch" and its Aviation code re-raised to "Orange."

This comes as observations of the volcano yesterday that the previously much smaller lava dome in the summit crater has resumed growth and now fills the floor of the crater.

A persistent thermal anomaly has been observed since September 3, probably marking the timing of resumed lava dome growth. The size of the dome as of August 30 when it appeared to have stopped growing was approximately 262 feet in diameter. The current dome is approximately 394 feet in diameter. If dome growth continues, lava flows onto the flanks of the volcano may develop but would not be hazardous to aviation. The presence of the lava dome increases the possibility of an explosive eruption, but does not necessarily indicate that one will occur. Short-lived explosions could produce an ash cloud that exceeds 20,000 ft above sea level. These events can occur without warning and may go undetected in satellite imagery for hours.

The team at the Alaska Volcano Observatory were unsure on September 2nd, whether the 6.8 earthquake had disturbed the apparent rest of the volcano. But, satellite information began to trickle in on the next day as the first of the anomalies since the down-grade of the volcano made itself known. That information had the volcano obscured by cloud cover so no determination could be made then. It wasn't until yesterday that a better view of the summit of the volcano could be seen.

Although no connection has been made, the 6.8 earthquake and its numerous after-shocks felt on and after September 2nd, may very well have been responsible for the current activity at Mount Cleveland.

There was another after-shock from the September 2nd quake again early this morning at 2:36 am measuring 4.4 magnitude.

quote:

Cleveland heading for explosive eruption with little warning?
A volcano in Alaska's Aleutian Islands has been in an unusual low-level eruption for two months, raising the specter of an explosive eruption with little warning, officials at the Alaska Volcano Observatory said on Friday.

Cleveland Volcano, a 5,676-foot peak located 940 miles southwest of Anchorage, continues to expel lava out its crater, a low-level eruption that began in mid-July, scientists at the Alaska Volcano Observatory said.

Satellite imagery shows a lava dome growing inside the volcano's crater. Satellite data also shows continued heat generated from the volcano, according to the observatory, a joint federal-state organization.

So far, there have been no signs of ash clouds. But those could come with little warning, scientists said.

"The big thing we're concerned about is an explosive eruption," said Steve McNutt of the University of Alaska at Fairbanks, a coordinating scientist for the observatory.

One worry is that the dome could seal off the crater vent entirely, causing pressure to build until it is released explosively, McNutt said. Or the dome could topple, triggering a molten flow down the mountain that releases gas and ash into the atmosphere while lava and rocks tumble, he said.

While Cleveland is one of Alaska's most active volcanoes — erupting about once a year over the past decade — its long-running lava flow and dome buildup is something different from past behavior, scientists said.
Past eruptions have been mostly brief and explosives, with relatively small ash clouds, said Chris Waythomas, acting scientist-in-charge at the observatory.

Interference with air travel is the most immediate risk posed by Alaska's volcanoes because the peaks lie directly in the flight path used by jets traveling between Asia and the U.S. West Coast.

Jet engines can be damaged or shut down abruptly when they suck in gritty volcanic ash.

quote:

Cleveland volcano starts oozing Lava
ANCHORAGE, Alaska — A volcano in Alaska's remote Aleutian Islands has begun oozing lava, a signal that the mountain could explode and send up an ash cloud that could threaten aircraft.

Satellite images show lava is building in the crater at the summit of 5,675-foot Cleveland Mountain on an uninhabited island about 940 miles southwest of Anchorage, according to the Alaska Volcano Observatory.

"It's forming a dome-shaped accumulation in the crater," said Chris Waythomas of the U.S. Geological Survey, the observatory's acting scientist in charge. "We call these things 'lava domes.' It looks like a muffin top."

Lava domes form a lid on a volcano's "plumbing," including the chamber holding the magma. When they grow big enough, lava domes become unstable and will sometimes collapse, decompressing the magma chamber and leading to an explosion, Waythomas said.

"They can seal up the conduit and prevent gasses from escaping and lead to an explosive event," he said.

Such an explosion from of the volcano on Chuginadak Island could send an ash cloud 20,000 feet or more into the air, the observatory said.

The nearest village, Nikolski, is on another island about 50 miles east and has 18 permanent residents. In previous eruptions of Cleveland Volcano, the village was not considered to be in harm's way.

"The plume would have to head directly to Nikolski to cause any problems," such as ash that could cause respiratory problems or damage engines, Waythomas said. If the village uses surface water for drinking, ash could temporarily foul it.

The larger threat from ash clouds is to aircraft.

Alaska's Redoubt Volcano blew on Dec. 15, 1989, and sent ash 150 miles away into the path of a KLM jet carrying 231 passengers. Its four engines flamed out. The jet dropped more than 2 miles, from 27,900 feet to 13,300 feet, before the crew was able to restart all engines and land the plane safely at Anchorage.

The Federal Aviation Administration and the airline industry get concerned for trans-Pacific flights when an ash cloud has the potential to exceed the 20,000-foot threshold, as Cleveland Volcano has done in the past.

"Generally anything above that altitude can be hazardous to overflying aircraft," he said.

quote:

Lava reached edge of Alaskan crater
Lava has reached the edge of a crater in a volcano in Alaska's remote Aleutian Islands, indicating the mountain could explode and send up an ash cloud that could threaten aircraft.

The Alaska Volcano Observatory says satellite images show lava at the edge of the crater rim of 5,675-foot Cleveland Mountain on uninhabited on Chuginadak Island, about 940 miles southwest of Anchorage.

Volcano monitors say if the dome continues to grow, it could overflow the rim and increase the possibility of an explosion.

The observatory says an eruption could send up an ash cloud 20,000 feet or more.

The nearest village, Nikolski, is on another island about 50 miles east and has 18 permanent residents. The village was not considered in harm's way in previous eruptions of the volcano.

quote:

AVO reported that during 5-6 and 9-11 October cloud cover over Cleveland prevented views of the lava dome in the summit crater. Partly cloudy satellite views during 7-8 October showed elevated surface temperatures at the summit. The Volcano Alert Level remained at Watch and the Aviation Color Code remained at Orange. No current seismic information was available because Cleveland does not have a real-time seismic network.

Geologic Summary. Symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited dumbbell-shaped Chuginadak Island in the east-central Aleutians. The 1,730-m-high stratovolcano is the highest of the Islands of Four Mountains group and is one of the most active in the Aleutians. Numerous large lava flows descend its flanks. It is possible that some 18th to 19th century eruptions attributed to Carlisle (a volcano located across the Carlisle Pass Strait to the NW) should be ascribed to Cleveland. In 1944 Cleveland produced the only known fatality from an Aleutian eruption. Recent eruptions from Mt. Cleveland have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks.

quote:

Cleveland sends ashcloud up to 15000 ft
ANCHORAGE, Alaska -- A volcano in Alaska's Aleutian Islands sent up an ash cloud Thursday that prompted scientists to increase the alert level for commercial aircraft traffic.

The Alaska Volcano Observatory said satellite images at 4:02 a.m. Alaska time showed Cleveland Volcano had spewed ash 15,000 feet into the air in a cloud that moved east-southeast. U.S. Geological Survey scientist-in-charge John Power called it a small explosion.

"It's not expected to cause a disruption to big international air carriers," he said.

However, it was significant enough to raise the alert level from yellow, representing elevated unrest, to orange, representing an increased potential of eruption, or an eruption under way with minor ash emissions or no emissions.

Cleveland Mountain is a 5,675-foot foot peak on uninhabited Chuginadak Island about 940 miles southwest of Anchorage. The nearest village is Nikolski on another island about 50 miles east. Previous eruptions of Cleveland Volcano were not considered a threat.

Scientists in July noted increased activity in the crater at the summit of the volcano. Satellite images showed lava building and forming a dome-shaped accumulation.

The Federal Aviation Administration and the airline industry get concerned for trans-Pacific flights when an ash cloud has the potential to exceed the 20,000-foot threshold, as Cleveland Volcano has done in the past.

The event Thursday drew strong interest from air carriers.

"Any time you put an ash cloud up into the atmosphere, the airlines, the air carriers, air freight companies -- it's a major concern," Power said.

The observatory is working with the University of Washington to monitor lightning above the mountain, which may signal a major ash plume.

quote:

Alertstatus Cleveland raised - New Lava dome visible
ANCHORAGE, Alaska — The warning level for a remote Alaska volcano has been raised after a new lava dome began forming, indicating the mountain could explode and send up an ash cloud that could threaten aircraft.

The Alaska Volcano Observatory on Tuesday elevated the alert status for Cleveland Volcano.

It said it was raising the Aviation Color Code to orange, which is one step below the highest warning of red.

An orange warning is characterized as "exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway with no or minor volcanic-ash emissions," according to the observatory.

130-foot lava dome
Officials said the new lava dome was spotted in the summit crater. The observatory said as of Monday, the dome was about 130 feet in diameter.

There have been no eruptions since Dec. 25 and Dec. 29, which destroyed the earlier lava dome built up over the fall.

quote:

Will an eruption disrupt Air Travel?
Mount Cleveland, a volcano in Alaska, has been exhibiting "eruptive activity" according to the Alaska Volcano Observatory (AVO). If it erupts, the volcano could spew ash into the air, which can potentially threaten intercontinental flight paths.

Trans-Pacific flights could head directly over the area of the potential explosion. Depending on the altitude of the ash cloud produced by the explosion, travel may or may not be impacted.

"It really depends on the height of the ash cloud from the eruption, as well as when it erupts," said AccuWeather.com Senior Meteorologist Michael Pigott. "If the cloud were to stay around 20,000 feet and hit the air on Tuesday, things wouldn't be too bad. But that would change as winds begin to pick up significantly on Wednesday."

"The volcano at Mount Cleveland exploded twice on Christmas Day and once on Dec. 29. If an explosion were to happen soon and be similar to those explosions, the ash cloud will probably end up in the 15,000- to 20,000-foot range," said Alaska Volcano Observatory Research Geologist Matt Haney. "Essentially, this explosion would probably not have much of an impact on international travel as it will most likely not exceed 30,000 feet, where most flights in the area would be traveling. That's what we're thinking right now."

With winds being more mild in lower elevations through Tuesday night in the region, the potential for the ash cloud to spread is relatively small. The higher elevations, however, are a different story.

"If you were talking about 30,000 to 40,000 feet, things would be different. Potentially, the ash could move quite a far distance. If the ash cloud goes higher, it could hit the jet stream and head out over Canada. Wind currents are very strong through Wednesday evening, but will ease off overnight. If the explosion happened then and reached that altitude, it probably wouldn't be as bad of a situation," said Pigott.

On Jan. 30, a 130-foot (40-meter) lava dome was first observed from satellite data after a month of little to no change. The diameter of the opening of the volcano is approximately 650 feet (200 meters). Since this lava dome formed, no observations of ash emissions or explosive activity have been reported.

"Think of a lava dome as a sort-of 'plug' that forms at the top of the conduit," Haney said. "Lava domes usually form in strata volcanoes. If the dome were to plug up the conduit completely, pressure could build up and lead to a new explosion. Generally, a dome is indicative of explosive activity. What we're trying to determine now is if this dome will be destroyed or if it's the final cap for this round of activity."

The most recent report from the AVO shows no evidence of ash emissions or elevated surface temperatures in partly cloudy satellite images over the past 24 hours. Additionally, there are no indications of any explosive ash-producing activity from the volcano. According to the AVO, eruptive activity at the volcano has slowed or even paused.

Still, the AVO warns that "intermittent, sudden explosions of blocks and ash" can occur at any time and ash clouds of up to 20,000 feet above sea level may form, and they have issued a volcano "watch," color code "orange."

"Since Mount Cleveland is on a small volcanic island in the Aleutian Island chain, we don't have real-time monitoring," added Haney. "We monitor with satellites, ground-based seismic monitors and infra-sound detectors. Nearby islands, however, do have real-time monitoring, and if a major explosion came from Mount Cleveland, we would know about it."

quote:

Lava dome Cleveland grows 25% in a week
The lava dome covering Mt. Cleveland volcano in Alaska has grown by 25 percent since last week. The dome was reported to be 40 meters across on Monday Feb. 6., and has now increased to 50 meters in size, according to the Alaska Volcano Observatory (AVO).

"We got indications from satellite data that the dome had grown slightly," Alaska Volcano Observatory Research Geologist Matt Haney said. "The recent expansion shows that growth has not ceased."

The current lava dome is much smaller than the previous dome.

"The previous lava dome that was removed by explosive activity on Dec. 25 and Dec. 29 covered most of the 200-meter-diameter summit crater. So, indeed it was larger than the current dome," said Haney.

Given that the current lava dome is still significantly smaller than the dome in December, does that mean the explosion would be smaller if it happened from this smaller lava dome?

"No, a larger dome doesn't necessarily mean a larger yield from the explosion," said Haney. "We're still expecting the same type of altitude for the ash cloud. It should interrupt Trans-Pacific flights."

quote:

Alaska: Kanaga active, also Cleveland
Add another Alaskan volcano to the list of recently restless systems. Kanaga, near Adak (50 km to the east), has been reportedly erupting over the weekend, with both a weak ash plume spotted via satellite and volcanic tremor showing up on the local seismic stations (however, the local station for Kanaga is down). All of this prompted AVO to raise the alert status to Yellow/Advisory over fears of larger explosive eruptions. It has been almost 17 years since the last confirmed eruption from Kanaga, a VEI 2 event that produced mostly explosive material. However, eruptions in 1994 did also produce lava flows – a pretty typical combination in these Aleutian stratovolcanoes.

Kanaga joins Cleveland as Aleutian volcanoes on elevated alert. Cleveland has seen its new summit dome continue to grow and has now reached ~60 meters in diameter. This continued growth increases that chance that an explosive eruption could occur at Cleveland if this dome blocks gases from escaping the volcanic conduit or the dome collapses as it grows larger – much like the explosive eruption in late December. The volcano remains on Orange/Watch alert status.

quote:

Alaska: The Alaska Volcano Observatory lowered the alert status at Kanaga from Yellow to Green over the weekend after potential eruption precursor activity waned. After the brief eruption on February 18 and a period of heightened seismicity, the volcano returned to background levels of activity since February 24. Cleveland volcano remains on Orange alert level with continued dome growth at the summit, although little change has been noted in recent satellite images of the volcano’s summit. Also, the Alaska Dispatch had one of the first articles I’ve seen marking the upcoming 100th anniversary of the Novarupta/Valley of 10,000 Smokes eruption. I’m sure we’ll see more of this was the June 6 anniversary approaches.

quote:

Blast shakes restless volcano in remote Aleutian Islands

A restless Aleutian volcano exploded Wednesday night and may have blown off a slow-growing lava dome that was building for months in its summit crater, volcanologists say.

Cleveland Volcano, 940 miles southwest of Anchorage, probably burped up a small amount of ash -- a potential hazard to trans-oceanic air travel -- but the ash did not appear to reach above 20,000 feet, said Steve McNutt, a researcher with the Alaska Volcano Observatory.

Because of its remoteness, harsh weather in the area and budget constraints, Cleveland Volcano does not have instruments on its flanks. As a result, scientists cannot listen to its inner rumblings. But distant seismometers and specialized microphones detected the explosion about 7 p.m. Wednesday, according to the observatory.

The explosion caused a displacement of air and an airwave traveled out from the volcano at the speed of sound, McNutt said. Instruments at volcanoes 60 and 90 miles away detected the explosion several minutes after it occurred, he said.

Clouds on Wednesday and today prevented clear satellite views, so scientists are not sure exactly how much ash may have shot out of the 5,676-foot volcano, which makes up the western half of Chuginadak Island.

"It is the Aleutians in winter, after all," McNutt said.

Either way, the researchers do not think the volcano poses an immediate threat to air travel.

McNutt thinks the explosion blasted away a lava dome building inside the volcano's summit crater. As the thick, pasty molten rock flows slowly into the crater, it piles up and plugs gas vents, he explained. An explosion can occur when the gas builds up enough pressure, McNutt said.

For now, the volcanologists are waiting for better views of the volcano to determine exactly what happened. Scheduled satellite passes in the near future should give them a better idea, McNutt said.

If it's true that the dome was removed, he said, the risk is lower that a larger ash- producing explosion might affect air travel. That is, until another dome builds up.

In December, a similar event cleared a lava dome that had been building up at Cleveland Volcano for two months. The brief explosion blasted volcanic ash up to about 15,000 feet, the observatory said.

Meantime, volcanologists are monitoring another volcano closer to home, one that hasn't erupted for at least 500 or 1,000 years, McNutt said.

A series of small earthquakes has been detected in recent months at Iliamna Volcano, in Lower Cook Inlet about 110 miles from Anchorage, according to the volcano observatory. Those earthquakes are typical for the ancient volcano and could be related to the movement of nearby glaciers, McNutt said. Still, more investigation, including a flight to measure gas emissions, is warranted, he said.

"Another question, which always dogs us in these situations, is if molten rock is involved," he said.

quote:

Iliamna volcano in Alaska seismic unrest
Since the middle of January 2012, seismic activity at Iliamna volcano has increased with more than usual numbers of earthquakes greater than magnitude 2.
It is common to have earthquake swarms in the vicinity of Iliamna, which are usually caused by magmatic intrusion at depth. The ongoing activity is being closely monitored by AVO seismologists. AVO for now has not raised the alert status, which officially remains at "green".
Similar swarms have last occurred in 1996-97, and there was no eruption then.

quote:

Alert level Iliamna volcano raised
ANCHORAGE, Alaska — Increased earthquake activity has prompted scientists to raise the alert level for an Alaska volcano.

The Alaska Volcano Observatory on Friday elevated the alert status for Iliamna (ill-ee-AHM'-nuh) Volcano, located on the west side of Cook Inlet, about 135 miles southwest of Anchorage.

Officials in a release say earthquake activity has been increasing at the volcano over the last three months and is above background level.

While a significant change, they say it's not certain if the earthquake activity is because of magna movement.

This doesn't mean an eruption is imminent, and could be similar to earthquake activity from September 1996 to February 1997 that didn't result in an eruption.

The observatory this week said there was a small eruption at Cleveland Volcano, located about 940 miles southwest of Anchorage.