Lake Toba

Exploring Tuk Tuk

2008-07-19T02:29:00.000-07:00

Early morning at Tuk Tuk on Samosir Island.

Tuk Tuk Peninsula is located on the eastern coast of Samosir Island, in Lake Toba. It is the main tourist village on the island, and it is here that tourists to Samosir find most of the accommodation, from simple guesthouses called losmen to upmarket resorts.

It is not difficult to understand why Tuk Tuk is the tourist centre of Samosir Island, for it is by far the most picturesque part of the island. When I was there, I stayed at Hotel Silintong, which sits on a promontory with breathtaking views of the lake. Every now and then, we could see boatmen rowing past our hotel.

Tuk Tuk is located across a bay from Tomok, another village where there are ferry services to Prapat. A small country road leads from the Tuk Tuk peninsula to the rest of Samosir Island.

We happened to have a few hours on hand, so we did a walking tour along the peninsula. Along the way, we found a number of losmen as well as souvenir shops. The scenery across the lake was great. At one point, I heard church bells. When I saw the locals dressed in their best clothes walking towards a village church, I realised it was Sunday morning and they were going for services. So I decided to join them, to see how church is like on Samosir.

The little church building was packed with worshippers. I found out later that its name was Gereja Santu Alfonsus. Some come by motorcycle, but the majority simply walked. I had the chance to take a look at their bible and hymn book. All are in their language. It was a marvellous experience to attend church in Tuk Tuk.

Tuk Tuk Photo Album

Lake Toba, as seen from Tuk Tuk peninsula.

The view from Tuk Tuk peninsula, far left, across Lake Toba towards Tomok, on the right.

Ferryboat crossing Bagus Bay with passengers going to Tuk Tuk peninsula.

The country road around Tuk Tuk peninsula

Left: View across Bagus Bay from Tuk Tuk peninsula.
Below: Boys of Tuk Tuk on the bicycles.

These boys have a school assignment: they have to go around Tuk Tuk looking for tourists so that they can practise their English.

On the north side of the Tuk Tuk peninsula, I came across these boys giving their motorcycle a washing.

A sign of joy in living.

Exploring Tomok

2008-07-19T02:28:00.001-07:00

Traditional Batak house in Tomok, with grain being dried in the yard, and a less-than-traditional satellite dish at the back.

Tomok is one of the main towns on Samosir Island, in Lake Toba. It has a jetty for ferries coming in from Prapat, which is 30 minutes away on the eastern bank of the lake.

Hugging the Tomok jetty are souvenir shops, again every store selling almost the same items. Tourists thinking of buying cheap t-shirts should try them out before purchasing. What I discovered was that the Indonesian sizes are much smaller than back home, so the same size might not fit.

The main draw of Tomok must surely be the King Sidabutar's tomb. Apart from that, there are also traditional Batak houses with the curved roor ridges to be found here. Further inland is a Batak Museum that was being made ready. When I visited, the workmen were putting on the finishing touches to the museum.

A short distance from the jetty, and within sight of it, is a church. While waiting for the ladies in our group to be done with their shopping, I went over to the church to explore it.

Another ancient Batak tomb, this one located near the lakeside in Tomok.

Exploring Samosir Island

2008-07-19T02:27:00.001-07:00

Rows of resorts and hotels in Tuk Tuk, Samosir Island.
Samosir Island is an island located more or less at the centre of Lake Toba. At 630 sq km, Samosir is just slightly smaller than Singapore, which is 714 sq km. Samosir holds the distinction for being the largest island within an island, and the fourth largest island within a lake.

Lake Toba is believed to have been formed 75000 years ago, following the biggest eruption ever known. A second eruption 30,000 years ago pushed up Samosir Island, and formed the peninsula that is now Prapat.

Samosir Island Photo Album

A Toba Batak village on Samosir Island.

A small island adjacent to Samosir near the village of Simanindo.

View of the Samosir landscape.

Exploring Prapat

2008-07-19T02:25:00.000-07:00

The town of Prapat, as seen from our chartered boat on Lake Toba. We stayed at the Danau Toba International Cottage, which is the row of building with red roofs at water's edge.
Prapat, also written Parapat, is a small town on the eastern shore of Lake Toba, about 170km from Medan, in North Sumatra. Since colonial times, Prapat has been a weekend getaway and resort town for those escaping the heat and bustle of Medan. In my opinion, although some places in Prapat, especially along the shore, is quite scenic, on the whole, it is not a pretty town. In fact, there is no good reason to remain long at Prapat. Despite being a tourist town for generations, there is actually little in terms of attractions that is available to visitors to Prapat, and tourists are well advised to proceed to Samosir Island.

I explored Prapat with a small group of AsiaExplorers members, on our way to Lake Toba. We spent a night here before crossing over to Samosir Island the following day. While in Prapat, we stayed at the Danau Toba International Cottage, a 2-star establishment which is already one of the better hotels in Prapat. It is centrally located with rooms right at the water's edge. The creative comfort was very basic. There was no air conditioning, so it was quite warm for us at night.

Our hotel is located close to the Prapat market, so it offered us an opportunity to explore and find out how the locals live. Prapat is situated on a hilly decline, and many of its houses cling to the slope, linked by the narrow hill roads. Their zinc roofs sprout a multitude of satellite dishes. There was a small number of shophouses in Prapat, but I could not find a single shop that sells guidebooks, maps or even postcards.

For want of something better to do, we chartered a boat to go out into the lake, where we enjoyed a lovely sunset view of Prapat and Samosir Island.

On the following morning, I walked along the edge of Lake Toba to explore another section of Prapat which is separated by the hills. I saw big sections of the lake overgrown with water hyacinths. There was another market on this part of town, but it lacks any particular charm to leave a lasting impression in me.

To reach Samosir Island from Prapat, we were provided with another chartered boat that took us sightseeing in different parts of Samosir Island. Otherwise, visitors can take the ferry that goes from Prapat to Tomok, one of the main villages on the eastern coast of the island.

Prapat Photo Album

The lanes in Prapat slope down towards Lake Toba.

The houses in Prapat hug the slope while sprouting a flowering of satellite dishes.

Boatman negotiating through a sea of water hyacinths.

Workman hauling boat back to shore in Prapat.

Exploring the Batak Museum

2008-07-19T02:20:00.001-07:00

A new Batak Museum was being set up in Tomok.

Batak Museum in Tomok is one of the three that I have visited. The other two are in Simanindo and Pematang Purba. Both the museums in Simanindo and Pematang Purba are former residences of Batak rulers, whereas the one in Tomok, although located a short walking distance from the Tomb of the Sidabutar kings is one specially set up to showcase the Batak culture in Tomok.

The Batak Museum in Tomok displays Batak handicrafts such as masks as well as household items including basketware, pots, spears, and tribal effigies. Also on display are musical instruments such as the gongs and drums. When I was there, the museum was still being made ready - I think it is not officially open to the public yet, but visitors are welcome to enter and admire the artefacts.

Batak Museum Photo Album

The items on display at the Tomok Batak Museum.

The Batak Museum in Simanindo used to be the former residence of the Simanindo ruler.

A Solu Bolon, or royal boat, is exhibited at the Batak Museum in Simanindo.

The Batak Museum of Pematang Purba, also a former royal residence, showcases Batak craftsmanship in their architecture. More details of this royal residence available on the Pematang Purba page.

Ambarita Photo Album

2008-07-19T02:18:00.000-07:00

Restored Toba Batak houses in Ambarita. Unfortunately the roofing does not match the architecture.

A closer view of the tribal houses reveal intricate carvings.

Victims awaiting their fate is imprisoned behind the wooden bars below this house.

This is either the tomb or monument to the Siallagan kings. It is at the entrance to the tribal village. Unfortunately I cannot determine it for sure.

This is another monument, or perhaps tomb, to Laga Siallagan, the first ruler of Ambarita.

With the help of a volunteer, our guide demonstrated how a victim is disemboweled.

And here, he showed where a victim is beheaded.

Tim standing at the stone passageway into the tribal village. Entrances are kept narrow to thwart intrusions.

Exploring Ambarita Stone Chair Village

2008-07-19T02:17:00.000-07:00

The stone chairs of Ambarita where tribal elders held council.
Ambarita is an ancient Batak tribal village on Samosir Island, in Lake Toba. It is located an hour's walk northwest from Tuk Tuk or about 20 minutes by boat. I visited it together with a small group of AsiaExplorers members.

What makes Ambarita interesting, from an anthropological standpoint, is that during ancient times the Toba Batak people of Ambarita practised a form of carnibalism. What remains today is the cluster of stone chairs where the village elders held council. Whenever an enemy was captured, the elders would invite the rulers of neighbouring villages to a conference, to determine the fate of the victim. The victim is held in behind bars under one of the houses.

If it is determined that the victim deserved death, he is taken to a dining table where he is clobbered to death. There is a boulder where the victim is beheaded. After that, he is chopped up, his flesh is cooked with buffalo meat, and served to the tribal council, who completed the meal with a beverage of the victim's blood!

We arrived at Ambarita by boat. From the jetty, we were first shown the tomb of Laga Siallagan, the first raja of Ambarita. From there, we were led to the ancient Batak village where there is a row of traditional Toba Batak houses. As I examined the houses, which are still used today, I find that many of them have zinc roofing, somewhat removing the romanticism I would associate with visiting this place. I suppose zinc roofing would be more long lasting, although I would have preferred that the villagers retained the original roofing which I assume should be ijuk thatch made from coconut fibre.

From the row of traditional houses, we moved on to view the stone chairs and the cage where victims are incarcerated. I am surprise to see that there is also a stone figure sitting on one of the chairs, and we had our photos taken with "him".

A short distance from the stone chairs is the place where victims meet their death. Our guide demonstrated how the Bataks go about with the procedure. He also showed us the Batak calendar and other tribal implements. On the hill above are the graves of the tribal elders as well as a monument to Raja Laga Siallagan. From the appearance of the monuments and graves, it appears that the tribal elders have embraced Christianity, but I could not determine whether these Christian elders are the ones who were still practising carnibalism.

Beyond the stone "human kitchen" are souvenir stalls selling T-shirts and other trinkets. My observation about all the souvenir stalls in Samosir island is that all of them seem to carry the same items. And I can name them: t-shirts and wood carvings. I could hardly find anybody selling good guidebooks on Samosir or Lake Toba anywhere in sight! Thus, I had to depend on information drawn from my guide as well as my own research down outside Lake Toba to furnish the information on this page.

Wellcome to Lake Toba

2008-07-19T02:14:00.000-07:00

Lake Toba, or Danau Toba in Indonesian, is the largest year-round lake in Southeast Asia. Although it is smaller in size than the Tonle Sap of Cambodia, unlike the Tonle Sap, Lake Toba is pretty consistent in its size. Also, being a volcanic lake, Lake Toba is much, much deeper than Tonle Sap. Hence, it holds much more water than Tonle Sap, 240 km³ vs about for Tonle Sap.

Scenic view of Lake Toba. Samosir Island is on the top left.
Lake Toba is approximately 90 km long and 900 m above sea level. The catchment area for Lake Toba includes peaks over 2000 m high. Being in the highlands, Lake Toba enjoys a cool temperature that averages 20ºC.

Lake Toba is said to have been created by the massive Toba eruption that happened about 71500 years ago. It is said to be the largest volcanic eruption to have occured in the last two million years. It threw up 2800 cubic km of volcanic material (a volume equal to over ten times all the water within Lake Toba today). In comparison, the 1980 eruption of Mount St Helen emitted just 1 cubic km of material. More recent movement of the magma chamber pushed Samosir Island and Uluan Peninsula above the surface of the lake. This is due to the upward pressure exerted by the unerupted magma.

Just like at Tonle Sap, a whole civilisation developed on the shores of Lake Toba in the form of the Toba Batak people who inhabits the lake and Samosir Island.

Prapat is a major town on the east shore of Lake Toba. It is located on a peninsula that juts into the lake. On Samosir Island, major villages include Tuk Tuk, Tomok, Simanindo and Ambarita. A scenic mountain road skirts Lake Toba on its eastern shore affording scenic views of the lake. One of the best viewpoints of the lake is located just out of the village of Tongging, close to the Sipisopiso Waterfall.

The Beautiful palace in Lake Toba

2008-07-18T22:03:00.000-07:00

Pangururan

Tomok

Tuk Tuk Siodang

Siallagan Ambarita

Simanindo

Limbong

Lake Toba Festival, 13 - 16 June 2008

2008-07-18T21:57:00.000-07:00

Lake Toba (In Indonesian: Danau Toba) is a lake, 100 km long and 30 km wide, and 505 m. (1,666 ft.) at its deepest point, in the middle of the northern part of the Indonesian island of Sumatra with a surface elevation of about 900 m (3,000 feet). It is the largest volcanic lake in the world.

At the same time, it is also an important tourism icon of Indonesia especially in the Province of North Sumatera. It is considered to be an important place for the native Batak people in North Sumatera.

The name suggest clearly that the festival will be centered in the area of the Lake Toba. The Festival comprises of several activities:

1. Lake Toba Cultural Parade, June 13, 2008 starting from Prapat Harbour to Prapat Open Stage
2. Cultural Performance, performance of traditional cultures of native cultures of Lake Toba, every afternoon at the Open Stage, Prapat
3. Lake Toba Stage: performance of contemporary/pop culture, every evening in several location around the lake.
4. Toba Culinary Festival
5. Lake Toba Art Exhibition, Parapat Exhibition Hall
6. Miss Toba Contest, at the Parapat Hotel

Besides the cultural events, sport and other events will also take place. Sport events include: International bicycles race, Lake Toba Marathon, chess competition, Toba Row 2008, Lake Toba Swimming Race.

Lake Toba: Batak culture and relaxing

2008-07-18T21:51:00.000-07:00

Danau Toba, or Lake Toba as we know it, is the largest lake in Southeast Asia. It was created by the eruption of a super volcano 75 thousand years ago. It is still surrounded by the crater edge of that volcano, and in the middle of the lake, volcanic activity created Samosir an island as big as Singapore. Attached to that island is a small peninsula, with the village of Tuktuk on it. This is the tourist destination of the area, where we enjoy the cool air, a dive in the lake, the relaxed atmosphere, and the local Batak culture.

Liberty of Lekjon

After the exciting bus and bemo ride to Parapat we meet Liberty. He tells us that the last ferry to Tuktuk leaves in an Hour. But not to worry, there is a small restaurant where we can eat something while Liberty tells us all about Tuktuk and his hotel Lekjon cottages. It appears that the ferry will drop us off at any hotel on Tuktuk we want, and since we like the leaflet of Lekjon, we decide to let us lead by Liberty.

In the dark the ferry brings us over lake Toba. It takes about half an hour during which we only see some lights and a small fire along the crater edge. The ferry stops at the bay next to the peninsula first, and then moves along the coastline to drop everybody at their desired destination. We see a lot of hotel names, but it is too difficult in the dark to see what they are like. Just in the middle of the peninsula is Lekjon, and we are easily convinced to at least spend one night here. We get a clean room, a warm shower, and a nice view for a low price, what else do we want?

At night we drink something in Lekjon’s restaurant. The personnel is friendly, and one of them starts playing the guitar. A few English guests know some songs, and Sabine also starts playing. It is a good start for our stay at Lake Toba, which promises to become a holiday during our world journey.

Where are the tourists et Lake Toba?

The next morning we make a walk around Tuktuk. Although Lekjon is okay, we like to know what alternatives are around. And we also like to explore the surroundings. We pass many hotels. Big ones, with large buildings, and small ones, with cosy cabins along lake Toba. Especially the big ones make a desolate impression, they seem to have almost no guests. And some of the small ones are closed all together, and so are many of the restaurants. It appears to us that lake Toba must have seen much more tourists in the recent past. Many stay away now because of September 11, and the independence struggle of Aceh in North Sumatra, not very far from Lake Toba.

The peninsula is larger than we expected. At different hotels we inspect the rooms, but it is all similar to Lekjon. We also stop at some souvenir shops. Many nice woodcarvings for low prices. The vendors are urging us to be something, they also feel the lack of tourists.

To the market

In the afternoon we take the ferry across lake Toba back to Parapat. There is a market there, and we have to go there to get some money. This time we have a seat on top of the boat, and inspect the hotels again, this time from the water. There are a few that could not be seen from the road. It is clear that Hotel Carolina is the most fancy hotel on Tuktuk. Nice cabins in traditional Batak style, including cane roofs, and a private pool created in the lake.

The market of Parapat isn’t much of an attraction. We quickly find the ATM and go back to the ferry with a bemo. Parapat isn’t very interesting, but it is a pleasant town. There are some hotels here as well, but again only a few tourists.

Historic Ambarita

We decide to rent a few mountain bikes to explore Samosir island, the main island in Lake Toba to which Tuktuk is attached. The main road goes around the island, and we enjoy great views until we reach the historic town of Ambarita. We enter the wall around the historic center via a small gate. We have to fill in our names in a guestbook, and pay a small fee. We are the only tourists in here, and from the guestbook we learn there are not many visiting these days. We wonder how the personnel here can live from the fees. Then a guide comes along offering his services. He tells us we can decide for ourselves how much we pay him afterwards. Yeah, right.

There are a few traditional Batak houses in a nice row. Although they’re not that traditional, since they have tin roofs. But at least they have the traditional shape, that resembles the traditional shape of the Minangkabau houses, or these of the Toraja people in Sulawesi. They all had the horns of the water buffalo for inspiration. One of the houses doubles as a small museum and the guide explains some tools there. From his explanations, we only remembered the Batak calendar, so is wasn’t much.

Cannibalism at the old courtyard

Most important part of Ambarita is the old courtyard. Under an old tree are a number of stone chairs in a circle where the village elders held council. Criminals who were convicted with the death penalty were led to the execution yard 50 meters further. This is a larger circle with stone chairs, and a large boulder on which the convicted would be tortured to scare away the evil spirits. Then, the victim would be killed, beheaded, and cut in pieces. The heart and liver were eaten by the king and elders, and every witness had to eat something as well. The blood served as a drink for everybody.

We pay our guide, not surprised he asks for more, and move on to the souvenir street. Lots of stalls with woodcarvings and vendors who are desperate to sell something. And only 2 tourists (us) as their prey. But we carry very little money, so we have to disappoint them all. Another sad result of the tourist decline at Lake Toba.

Graves of Tomok

We hop on our bikes and follow the road to Tomok. Main attraction in this village is the grave of the king. Or actually there are more graves, and it is unclear to us which one is which. There are some stone figures around the graves, but no guide to explain things. A little further is a large doll on a stage. The story goes that a former king was so sad for the death of his son, that he ordered a dancing doll. The dancing of dolls became a tradition at funerals.

In Tomok are a lot of souvenir stalls as well. This time especially with clothes and other stuff. But again, no tourist around, and we are the only prey. So we don’t stay long, hop on our bikes and go back to Tuktuk, enjoying the views over Lake Toba.

Cinema

Tuktuk has its own cinema. An Englishman who lives here permanently, created a business with the copied video CD’s which are for sale everywhere in Southeast Asia. He has a large collection for rent, or you can watch them in a small room with large TV. We are watching “The Lord of the Rings” here. The copy was obviously made in an actual cinema: we can hear the laughter of the audience, and once in a while there is a shadow passing by. Amazing how the illegal copying industry works here.

In order to explore more of Samosir, we hire some motorbikes. After some instructions, we leave while the people shout at us to drive on the left side of the road, something we would already forgot. Easily we pass the many hills on our way to the first target: Samanindo. Here is a the Batak museum of Samosir located. After a little search, we find it just in time for an dance exhibition.

Batak dance

In front of an open terrain a more tourists are gathered than we saw in total the last couple of days. And in front of a scale model of a traditional Batak house are a group Batak people dancing. Well, dancing is a big word for the small movements they make. The program indicates multiple dances, but we see little variation. When some tourists join them, we hardly see a difference. And then a dancing doll enters the scene, making more moves than the dancers themselves. The tourists are supposed to give a donation to the doll, which is rewarded with a loud “Horas”. And that is the most exciting part of the exhibition.

The accompanying Batak museum isn’t much either. A little disappointed we hop pack on our motorbikes and move on. What amazes us most is that this place attracts most of the tourists around Lake Toba.

We move on along the outside of the island, passing many traditional houses, most of them with zinc roofs. Also many impressing grave towers, with on top of them a miniature traditional house.

Hot Springs

As we approach the other side of the island, the mainland comes in sight. A large white spot on the crater edge draws our attention. It almost seems like a ski trail, but we suppose it must be chalk or sand. A little later we arrive at the village where the island is connected to the main land by a small bridge. In fact, the bridge was only needed since the Dutch dug a canal to separate the island from the main land in 1906. We pass the bridge and drive up to search for our next goal: the hot springs. The closer we get, the more we realize the white spot is where we will find the hot springs.

The hot springs are accompanied by a number of restaurants and a large parking lot. But there are not many tourists. At one of the restaurants we park our motorbikes and order a meal. While we wait we see a little girl playing with to chicks, one of them bright yellow, the other bright green. Funny little animals, although it is sad that they probably have no mother and are obviously artificially colored.

After lunch we search for the hot springs. Every restaurant appears to have a bath of swimming pool fed with hot water from the springs, but we want to find the springs themselves. So we climb up, until we reach a restaurant that only lets us through if we order something. Here is a pool as well, but also a natural bath in the rocks. And as we climb up, we reach the actual source of the hot springs. In some kind of white moon landscape there is a stream of hot, yellow water. It is boiling up from the rocks, although we cannot see exactly where.

After a lovely, purifying, very hot bath, and a cola at the restaurant, we descend to our motorbikes. Although there is a market in the village we pass, we decide to go back to Tuktuk. It takes us two hours to go back, including a few stops for a beautiful view and a drink. We are back before dark, so we can cool off in the lake.

More Batak dance

That night there is a traditional dance performance in one of the restaurants of Tuktuk. We are convinced that there should be more to it than the slow motion dance we saw that morning, we decide to have a look. But what we see is even worse than that. Odd, since the traditional music sounds happy and dynamic.

After the dance there is a singing performance. Five men are putting all their energy in a few nice songs. Quite a contrast to the dance performance. The surprise is complete when the dancers invite the audience to swing with them. So they can actually dance enthusiastically, although it is not very traditional.

Woodcarving course

Having seen most of the sights around Lake Toba, we search for an alternative activity. We find a cooking course, but that one is a bit expensive. A woodcarving course, however, is cheap so we join a few souvenir makers. We get to pick something we like in order to try and copy it. After some instructions how to cut, we try for ourselves. Bit by bit our blocks of wood get some shape. Our teachers watch, adjust, and show how to continue.

Sabine’s mini mask is almost done. After sanding it, it can be polished and varnished. Patrick’s puppet takes a little longer, but after lunch, when our hands can be relieved from the cramps, it can be finished as well. Sabine has continued with carving her name, and begins with carving a guitar. Patrick tries a gecko. But then the fun is over. The leg of the gecko breaks, and the knife hits his hand. There is a lot of blood, but after binding it, it seems to be okay. But it is clear that we have not found a new occupation.

Tuktuk restaurants and hotels

Most of the evenings we dine at the restaurant of Lekjon. But we do want to try something different. So we walk the island, searching for nice restaurants. Around Lekjon are a few of them, but there are just a few people every where, And the further we walk, the sadder it gets. Many restaurants wait for the first guests of the evening, others are already closed. We do find one restaurant that draws more public. It is the Bamboo restaurant, with nice decoration (bamboo obviously), good food and nice music. According to Roy Bamboo, the owner, there are many guests every night. It seems to be the exception to the rule that business is bad around Lake Toba these days.

As we have seen and explored every aspect of Lake Toba it is time to move on. It was a nice relaxing week with nice activities. It is a pity that the locals are desperate because of the decline in number of tourists. Once, there were probably too many tourists, but too little is not good either, for the great destination that Lake Toba actually is.

Lake Toba Geology

2008-07-18T21:49:00.001-07:00

Geology

In 1949 the Dutch geologist Rein van Bemmelen reported that Lake Toba was surrounded by a layer of ignimbrite rocks, and that it was a large volcanic caldera. Later researchers found rhyolite ash similar to that in the ignimbrite around Toba (now called Young Toba Tuff to distinguish it from layers deposited in previous explosions) in Malaysia and India, 3,000 km away. Oceanographers discovered Toba ash, with its characteristic chemical "fingerprint", on the floor of the eastern Indian Ocean and the Bay of Bengal.

The eruption

Main article: Toba catastrophe theory

Location of Lake Toba shown in red on map.

The Toba eruption (the Toba event) occurred at what is now Lake Toba about 67,500 to 75,500 years ago.^[2] It had an estimated Volcanic Explosivity Index of 8 (described as "mega-colossal"), making it possibly the largest explosive volcanic eruption within the last twenty-five million years. Bill Rose and Craig Chesner of Michigan Technological University deduced that the total amount of erupted material was about 2800 cubic km (670 cubic miles) — around 2,000 km³ of ignimbrite that flowed over the ground and around 800 km³ that fell as ash, with the wind blowing most of it to the west. By contrast, the 1980 eruption of Mount St. Helens ejected around 1.2 cubic km of material, whilst the largest volcanic eruption in historic times, at Mount Tambora in 1815, emitted the equivalent of around 100 cubic kilometres of dense rock and created the "Year Without a Summer" as far away as North America.

The Toba eruption was the latest of a series of at least three caldera-forming eruptions which have occurred at the volcano. Earlier calderas were formed around 700,000 and 840,000 years ago.^[3]

To give an idea of its magnitude, consider that although the eruption took place in Indonesia, it deposited an ash layer approximately 15 cm (6 in) thick over the entire Indian subcontinent; at one site in central India, the Toba ash layer today is up to 6 m (20 feet) thick^[4] and parts of Malaysia were covered with 9 m of ashfall.^[5] In addition it has been calculated that 10¹⁰ metric tons of sulphuric acid was ejected into the atmosphere by the event, causing acid rain fallout.^[6]

Landsat photo of Sumatra surrounding Lake Toba

The subsequent collapse formed a caldera that, after filling with water, created Lake Toba. The island in the center of the lake is formed by a resurgent dome.

Though the year can never be precisely determined, the season can: only the summer monsoon could have deposited Toba ashfall in the South China Sea, implying that the eruption took place sometime during the northern summer.^[7] The eruption lasted perhaps two weeks, but the ensuing "volcanic winter" resulted in a decrease in average global temperatures by 3 to 3.5 degrees Celsius for several years. Greenland ice cores record a pulse of starkly reduced levels of organic carbon sequestration. Very few plants or animals in southeast Asia would have survived, and it is possible that the eruption caused a planet-wide die-off. There is some evidence, based on mitochondrial DNA, that the human race may have passed through a genetic bottleneck within this timeframe, reducing genetic diversity below what would be expected from the age of the species. According to the Toba catastrophe theory proposed by Stanley H. Ambrose of the University of Illinois at Urbana-Champaign in 1998, human populations may have been reduced to only a few tens of thousands of individuals by the Toba eruption.^[8]

More recent activity

Children playing in Lake Toba

Smaller eruptions have occurred at Toba since. 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.^[9]

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^[10] 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.^[11] Other earthquakes have occurred in the area in 1892, 1916, and 1920-1922.^[12]

Lake Toba lies near a fault line which runs along the centre of Sumatra called the Sumatra Fracture Zone.^[13] 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 September 12th, 2007, a magnitude 8.4 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.

Where is Lake Toba

2008-07-18T21:38:00.000-07:00

Lake Toba (Indonesian: Danau Toba) is a lake, 100 km long and 30 km wide, and 505 m. (1,666 ft.) at its deepest point, in the middle of the northern part of the Indonesian island of Sumatra with a surface elevation of about 900 m (3,000 feet), stretching from 2.88° N 98.52° E to 2.35° N 99.1° E. It is the largest volcanic lake in the world.