A portent of things to come? ; increased volcanic and earthquake activity in Sumatra

**kingwilly** · 02-09-2009, 11:25 AM

Seems like there is an article a day in the papers and news regarding earthquakes in Sumatra. Here's today from Jakarta Post

Wednesday, September 2, 2009 11:17 AM

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5.3 quake jolts West Sumatra

The Jakarta Post , Jakarta | Wed, 09/02/2009 8:16 AM | National
A 5.3 magnitude earthquake jolted Mentawai Islands, West Sumatra early Wednesday morning, in the latest of a series of earthquakes that have hit the area.

The moderate quake occurred at 6:47 a.m. local time, in the islands' water.

The Meteorology, Climatology and Geophysics Agency reported that the quake's epicenter was located 124 kilometers southwest of Padang, and 10 kilometers below the seabed.

Quakes and aftershocks have struck West Sumatra and the towns surrounding the provincial capital of Padang since last month in apparently increasing tectonic activity. (dre)

We also know that Krakatoa Volcano has been increasingly more active and violent since I visited last year, in fact, it is closed to visitors now, and almost every evening lava flows can be observed....

Is this a sign of a big eruption and/or earthquake ?

**lingmau** · 02-09-2009, 12:05 PM

Nah, they have shakes of that sort of size all the time in Sumatra, just take a look at the USGS website.

And krakatoa is miles away from Sumatra, it's east of Java - no relationship at all. Lake toba on the other hand...

**StrontiumDog** · 02-09-2009, 12:11 PM

Well it is one of the most geologically active areas of the world. I guess we will find out soon enough, as it is totally unpredictable.

DaffyDuck · 02-09-2009, 12:15 PM

I guess I won't be booking my visit to Krakatoa anytime soon, then...

**kingwilly** · 02-09-2009, 12:18 PM

Originally Posted by lingmau

And krakatoa is miles away from Sumatra, it's east of Java - no relationship at all.

I beg to differ, it is in the centre of the Sunda Straits. More or less equal distance from Sumatra and JAva.

**robuzo** · 02-09-2009, 12:33 PM

Toba was mentioned above and I decided to Wiki it to see what sort of activity has been detected in/around the Toba caldera recently. For some reason I thought it was dead; or maybe that was just wishful thinking. I spent a great two weeks there many years ago, and in my mind it remains a peaceful place.
Lake Toba - Wikipedia, the free encyclopedia
"Smaller eruptions have occurred at Toba since (go read about the big one if you've never heard of it). The small cone of Pusukbukit has formed on the southwestern margin of the caldera and lava domes. The most recent eruption may have been at Tandukbenua on the northwestern caldera edge, since the present lack of vegetation could be due to an eruption within the last few hundred years.[15]
Some parts of the caldera have experienced uplift due to partial refilling of the magma chamber, for example pushing Samosir Island and the Uluan Peninsula above the surface of the lake. The lake sediments on Samosir Island show that it has been uplifted by at least 450 metres[9] since the cataclysmic eruption. Such uplifts are common in very large calderas, apparently due to the upward pressure of unerupted magma. Toba is probably the largest resurgent caldera on Earth. Large earthquakes have occurred in the vicinity of the volcano more recently, notably in 1987 along the southern shore of the lake at a depth of 11 km.[16] Other earthquakes have occurred in the area in 1892, 1916, and 1920-1922.[9]
Lake Toba lies near the Great Sumatran fault which runs along the centre of Sumatra called the Sumatra Fracture Zone.[9] The volcanoes of Sumatra and Java are part of the Sunda Arc, a result of the northeasterly movement of the Indo-Australian Plate which is sliding under the eastward-moving Eurasian Plate. The subduction zone in this area is very active: the seabed near the west coast of Sumatra has had several major earthquakes since 1995, including the 9.3 2004 Indian Ocean Earthquake and the 8.7 2005 Sumatra earthquake, the epicenters of which were around 300 km from Toba.
On 12 September 2007, a magnitude 8.5 Earthquake shook the ground by Sumatra and was felt in the Indonesian capital, Jakarta. The epicenter for this earthquake was not as close as the previous two earthquakes, but it was in the same vicinity."

**kingwilly** · 02-09-2009, 12:43 PM

I thought so too, but generally one needs no volcanic activity for a period of about 25,000 years for a volcano to be declared extinct, rather than dormant.

Originally Posted by robuzo

he most recent eruption may have been at Tandukbenua on the northwestern caldera edge, since the present lack of vegetation could be due to an eruption within the last few hundred years.[15]

on that scale well and truly still active.

**kingwilly** · 02-09-2009, 12:46 PM

according to this guy Krakatoa is only 9th on the list. I've seen other scientific lists that have Toba, Krakatoa and Bromo in the top 5.

Largest Known Holocene Volcanic Eruptions

Year Volcano Location Ejecta Remarks
4650 B.C. Mount Mazama Oregon 100+ Formed Crater Lake
4300 B.C. Kikai Ryukyu Islands, Japan 100+ Pyroclastic flows traveled 100 km, reached southern Japan. Southern Kyushu devastated.
1470 B.C. Santorini Greece 10+ Destroyed Minoan civilization
186 A. D. Taupo New Zealand 80+ Pyroclastic flows travelled 100 km 260 Ilopango El Salvador 10+
536 Rabaul New Guinea 10+ Global climatic effects
850 Hekla Iceland 10+
1010 Baitoushan China-Korea 150
1783 Laki Iceland 1 Largest historic fissure flow
1815 Tambora Indonesia 150 Global climatic effects
1883 Krakatau Indonesia 20+ Blast heard 5,000 km away
1912 Katmai Alaska 10+ Ejecta refers to cubic kilometers of ash erupted.

All figures are estimates. Since 10,000 B.C., over 50 eruptions are known to have vented more than 10 cubic km of ash (2006 data from the Smithsonian Global Volcanism Program). Laki, 1783 is also included as the largest historic lava flow.

Dates of first six events are from radiocarbon dates and are approximate.

Much larger events are recorded in the geologic past but we cannot claim a complete record. A few examples:

70,000 years ago, Toba, Indonesia. About 500 cubic kilometers of ash.
700,000 years ago, Long Valley, California. About 500 cubic kilometers of ash.
700,000, 1.4 million and 2.1 million, Yellowstone, Wyoming. About 500 cubic kilometers of ash.
Miocene: huge ash eruption, probably centered in the Snake River volcanic center; wind-blown ash suffocated and buried animals in Nebraska, but not as an immediate result of the eruption.
15 million years ago: Columbia Plateau flood basalts.
240 million years ago: Siberian flood basalt eruptions. Suspected by some as the cause of the Permian mass extinction.
Ordovician (450 million years ago): Vast ash falls blanketed all of eastern North America and Scandinavia, which at that time were close together. The probable source was somewhere southeast of present Alabama. Single ash beds can be traced from Alabama, where they are meters thick, to Minnesota, where the thickness is a few centimeters.

Source, T. Simkin and others, 1984, Volcanoes of the World, Stroudsburg, PA, Hutchinson Ross, 232p.

**kingwilly** · 02-09-2009, 12:48 PM

Greatest Killer Volcanic Eruptions

Date Volcano Location Deaths Remarks
April 10-12, 1815 Tambora, Indonesia 92000 Ash falls, Tsunami, Disease, Starvation
Aug. 26-28, 1883 Krakatoa Indonesia 36000 Ash falls, Tsunami May 8,
1902 Mount Pelee Martinique 28000 Pyroclastic Flow Nov. 13,
1985 Nevado Ruiz Colombia 23000 Mudflow
Aug. 24, 79 A.D. Vesuvius Italy 16000 Ash falls and Pyroclastic Flows. The famous Pompeii eruption.
May 21, 1792 Unzen Japan 14500
1586 Kelut Java 10000
June 8, 1783 Laki Iceland 9350 Fissure Flow, Disease, Starvation
May 19, 1919 Kelut Java 5000
Dec. 15, 1631 Vesuvius Italy 4000
April 24, 1902 Santa Maria Guatemala 4000 Ash falls, Disease, Starvation
Aug. 12, 1772 Papandayan Java 3000
Jan. 27, 1951 Lamington New Guinea 3000 Pyroclastic Flow. Volcano was not known to be active before the eruption.
Mar. 28, 1982 El Chichon Mexico 1880 Ash falls Aug. 21,
1986 Lake Nyos Cameroon 1700 Carbon dioxide emission from volcanic lake
Jan. 10, 1977 Nyiragongo Congo 70 - 100's? Lava flow from sudden drainage of lava lake.

Note the near absence of reference to lava flows, which rarely result in fatalities. Even the great Laki fissure flow of 1783 produced casualties mostly by ecological disruption.

Before the advent of telecommunications and air transport, ecological disruption was the major cause of loss of life in eruptions, with building collapse due to shaking and ash fall probably next most important.

The 1977 event from Nyiragongo is probably the largest recorded direct loss of life from lava flows. Nyiragongo presents the paradox of a steep-sided stratovolcano with extremely fluid lava, possibly because of a recent change in magma composition. When the crater wall failed, lava flows moved downhill at up to 100 km/hour, overwhelming villages without warning. The disaster happened at night, catching many people asleep.

In 2002 a flow destroyed nearly half of the city of Goma (population several hundred thousand) and caused some fatalities, easily the worst invasion of a city by lava flows in history.

**kingwilly** · 02-09-2009, 09:34 PM

Rather prophetic thread to start today...

**lom** · 02-09-2009, 09:47 PM

You better don't do these kind of threads.

**Begbie** · 02-09-2009, 09:51 PM

Whole lot of shaking going on. Today's earthquake was in the subduction zone south of Java.

**baldrick** · 02-09-2009, 10:43 PM

Originally Posted by kingwilly

Rather prophetic thread to start today...

Originally Posted by lom

You better don't do these kind of threads

eh ? do one on new zealand KW

**Michael** · 03-09-2009, 12:07 AM

Rightly so, driving through Southern NZ the roads were dug into pummice kilometres deep. From less than 200 years ago.

Rotarua is basically an active volcano.

People 'complain' about vents opening in their back gardens.

But they are mostly retired pensioners living there, so they don't really care.

I was amazed though.

**kingwilly** · 03-09-2009, 03:59 AM

Wales or Noo Ziland? Hmmmmm which one to do first?

**Marmite the Dog** · 03-09-2009, 08:31 AM

Originally Posted by kingwilly

according to this guy Krakatoa is only 9th on the list.

It's in date order, you knob.

**kingwilly** · 03-09-2009, 09:51 AM

Originally Posted by Marmite the Dog

It's in date order, you knob.

That's got to be one of my biggest fas paux to date.....

**crippen** · 03-09-2009, 09:56 AM

Originally Posted by kingwilly

Originally Posted by Marmite the Dog

It's in date order, you knob.

That's got to be one of my biggest fas paux to date.....

And not even a middle of the night post.

**Nawty** · 03-09-2009, 09:57 AM

Originally Posted by DaffyDuck

I guess I won't be booking my visit to Krakatoa anytime soon, then...

Guess not....the hookers there are all covered in ash hey ?

**Mid** · 27-11-2010, 11:31 AM

Indonesia's Mount Bromo erupts mildly
27 November 2010

A tourist stands at a view point overlooking Mount Bromo volcano.

JAKARTA: Indonesia's Mount Bromo volcano in eastern Java belched hot ash into the air in a low-level eruption on Saturday.

Mount Bromo, a popular tourist attraction, began rumbling earlier this month and the government issued an alert over heightened danger levels in the area on Tuesday.

"Bromo has shot gray ash up to 700 metres (2,300 feet) into the sky this morning. It was a low-level eruption," volcanologist Agus Budianto said.

The volcano also belched ash on Friday afternoon, in which it shot ash up to 500 metres.

"Nobody was hurt and evacuation is not needed at this time. We hope that there won't be an explosive eruption from Bromo," Budianto said.

Bromo erupted in 2004, killing two people.

Indonesia's most active volcano, Mount Merapi, has killed more than 320 people since it began erupting late last month.

Unlike Merapi, the countryside around Bromo is not densely populated as it lies within the Bromo-Tengger-Semeru National Park.

channelnewsasia.com

**PaulBunyon** · 27-11-2010, 01:31 PM

You'll survive. Things sure do seem to be shaking in lots of places.

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