TUES OCT 11: Canaries volcano prompts evacuation
Seismic activity now suggests the risk of another eruption closer to the coast, according to the director general of the Canaries’ emergency commission, Juan Manuel Santana.
“An eruption in shallower waters would produce a greater risk because of the greater interaction of the water with the magma,” he warned.
“We must continue to follow how the phenomenon develops, what we are putting in place is simply a preventative measure…” (More)
Update: Oct 12: 20:04 UTC: 2 new eruption locations detected this afternoon (Latest News)
More: Only the Spanish media is covering the El Hierro story...
For our Spanish speakers: This is from lasexta.com
IS EL HIERRO About to Blow?
According to John Moore, in a recent interview with Dr. Bill Deagle on the Nutrimedical Report, there is an increased possibility of a super mega-tsunami coming from the Canary Islands in the coming weeks—as the alert levels threatens to go red. The island of El Hierro is bracing itself for a possible volcanic eruption.
A 4.3 magnitude earthquake struck El Hierro late on Saturday night. It was the strongest earthquake to be recorded on the Spanish island since an unprecedented earthquake swarm commenced during the summer. (Instituto Geografico Nacional)
The Instituto Geografico Nacional (IGN) has reported an increase in the intensity of earthquakes recorded on the small Canary Island, during the last 48 hours. The number of earthquakes recorded since July 17 , 2011 on El Hierros has now reached 10,000, figures from the IGN confirm.
Meanwhile, scientific research is predicting that an eruption of the Cumbre Vieja volcano, at La Palma in the Canary Islands would result in a massive mega-tsunami that would reach the East Coast of America. (More)
OCTOBER 10: Canary Island Swarm Reaches 4.0+ Magnitudes
Today’s event on the Canary Islands would warrant a shift in alert status. There is an ongoing swarm of earthquakes on the Canary Island of El Hierro. As of today, magnitudes have reached 4.0—4.4. As a result, this should raise the alert level to “code red” and they will most likely evacuate the entire Island.
When volcanic seismic magnitudes reach this threshold of 4.0+, it suggests an escalation of magma with the potential of eruption. Furthermore, in the case of the Canary Islands, the real danger relates to a massive landslide into the Atlantic causing a mega-tsunami. This has historically occurred three times in the last 50,000 years. (More)
SEPTEMBER 29: RESIDENTS living near a volcano on Spain’s Canary Islands have been moved from their homes because of fears it is about to erupt. The Pico de Malpaso on El Hierro island has been rumbling and spitting rocks since July.
A resident named Herminio Barrera told Agence France Presse:
“I have never felt shaking like it. I notice it especially at night. We can also hear a rumbling and sounds from deep down. I am staying calm but there are people who are more worried, particularly those with children. We are very close to the mountain. My father-in-law left yesterday.”
The regional government says it is on a state of pre-alert and has stocked up on medical supplies and drinking water. According to Agence France Presse, local authorities are establishing an emergency shelter that can hold up to 2000 people.
Over the last seven days of activity, 1006 earthquakes have occurred. It was when magnitudes of 3.0 and higher were registered; the Spanish National Geographic Institute raised the alert level to Yellow, and began evacuation of El Hierro Island which is part of the Canary Island chain.
The Spanish National Geographic Institute has recorded 8,000 tremors since July 19, most of them too small to be felt, but one recorded overnight on Wednesday reached 3.4 magnitude. The swarm occurred at in the northwest of the island at the location of a landslide that created a 100-meter high tsunami about 50,000 years ago.
If this trend continues to worsen, there could be implications for America’s east coast…
A Collapsing Canary Islands Volcano Would Devastate USA
The Cumbre Vieja volcano on La Palma, in the Canary Islands, is currently in a dormant stage, but will almost certainly erupt again in the future. If such an eruption causes the western flank to fail, a megatsunami will be generated.
La Palma is currently the most volcanically active island in the Canary Islands Archipelago. It is likely that several eruptions would be required before failure would occur on Cumbre Vieja. However, the western half of the volcano has an approximate volume of 500 cubic kilometers and an estimated mass of 1.5 trillion tonnes.
If it were to catastrophically slide into the ocean, it could generate a wave with an initial height of about 1,000 metres (3,281 ft) at the island, and a likely height of around 50 metres (164 ft) at the Caribbean and the Eastern North American seaboard when it runs ashore eight hours later. Tens of millions of lives would be lost as New York, Boston, Baltimore, Washington D.C., Miami, Havana, and many other cities near the Atlantic coast are leveled…
More: Geological evidence for a large landslide in Tenerife...
Summary: This post provides a brief review of a new paper that describes a newly discovered catastrophic landslide deposit in Tenerife. (From: AGU Blogosphere)
One of the most intriguing but poorly understood landslide types is that of the volcanic flank collapse. This is one of those rare occasions in which the geological term actually does a pretty good job of describing the phenomenon. In a volcanic flank collapse, the side of a volcano fails, usually catastrophically, generating a landslide (look at the comparatively small landslide at Casita to see just how damaging these landslides can be). These slides can be really big – tens or even hundreds of cubic kilometres – and they can travel huge distances along the sea floor. Such failures grabbed attention a few years ago due to the potential (overstated, in my opinion) for generating a catastrophic tsunami.
However, we understand such phenomena really poorly. There are a number of reasons for this, principally that: a. They occur rarely (globally about one in every 25 years on average), so actually recording one is a challenge; and b. the remains tend to lie in a very dispersed state on the floor of the deep ocean. Fieldwork at 4 km water depth remains difficult, even if you are really good at holding your breath.
However, it is one particular aspect of these landslides that remains elusive, but is crucially important. This is the trigger of the collapse event (i.e. of the landslide itself). Numerous mechanisms have been proposed, including sea level change, climate change, hydrothermal pressure, intrusion of volcanic material, and various others. It has proven very difficult to ascertain the importance of each of these. This is an important question if we are to reliably estimate the hazard associated with future potential collapses.
In a paper published in Geology this month, Harris et al. 2011 report a very interesting find on the island of Tenerife, one of the Canary Islands. This is the remains of an ancient collapse event on the south-eastern part of Cañadas volcano. The landslide deposit, which is up to 50 metres thick, has been mapped across a large area – 90 square kilometres – and this is just the onshore component of the mass, which may extend another 50 km offshore. The deposit consists of a classic debris avalanche material, with large (typically up to 12 m long axis), shattered blocks in a highly disrupted, unsorted matrix. This is typical of a highly energetic, very large collapse event. Intriguingly, in the upper part of the deposit some fluviolacustrine (water/lake) sediments are found in the remains of hollows, indicating that in the aftermath of the landslide shallow lakes formed on the surface, presumably as a result of blockages created by the landslide. Associated with the landslide deposit are the remains of pyroclastic flows.
This is really interesting in itself, but the very well-preserved deposit allows both highly precise dating and a reconstruction of the events that occurred. The dating yields a date of about 733,000 years ago, with an error of just 3,000 years. So, the sequence of events is interpreted as being:
1. An eruption event, termed the Helecho eruption started in the form of an explosive event that showered ash and then pyroclastic material across the local area;
2. A dome grew on the volcano;
3. This dome collapsed catastrophically, generating a landslide that travelled 17 km to the shoreline, and then probably much further in the ocean;
4. Subsequent eruptions draped further pyroclastic, and then pumice, deposits on the surface of the landslide, and rainwater collected in hummocks to form small lakes;
So, in this case the volcanic flank collapse was triggered by a large, explosive volcanic eruption. Interestingly, the authors note that the landslide collapse left a gap in the rim of the caldera which subsequently channeled pyroclastic deposits to the south-east.
Of course this paper does not solve the question of what triggers volcanic flank collapses, but it is an important data point that validates one of the most likely mechanisms. It also provides a great opportunity to study these landslides in detail, which should give us a much greater insight into the dynamics of these immense mass movements.
Harris, P.D, Branney, M.J., & Storey, M. (2011). Large eruption-triggered ocean-island landslide at Tenerife: Onshore record and long-term effects on hazardous pyroclastic dispersal Geology, 39 (10), 951-954.
Source: AGU Blogosphere