The Lives of Lake Baikal
It is said that a huge stone fell from the sky like they do now, sometimes. While it was falling it became red hot. When it hit the earth there was a great rainfall. Earth, stone, and water came to a boil and in that turmoil Lake Baikal was born. (One of several creation legends of Lake Baikal)
Far from the ocean lies this unique lake. The purity and clarity of the water is legendary. The local name is ‘the Old Man’, or ‘the Sea’, or just ‘He’. Anywhere else, this is known as Lake Baikal. The locals have a point: no other lake is anywhere this size, no other lake is this ancient, and no other lake has its seals. It hardly needs a name. Lake Baikal is the closest we have to a fresh-water sea, Russia’s Galapagos, an exhibit of nature and geology alternating between a frozen wonderland and a flowering spectacle, ravaged by earthquakes, surrounded by plains and mountains, and blessed with a smattering of volcanoes. One day this may become our sixth ocean. If this happens, expect those volcanoes to flower. But that gets ahead of the story.
Lake Baikal is only ever described in superlatives. It is the world’s deepest lake, with the clearest water on Earth. There are 2000 kilometer of shoreline. Although not the largest by surface area (last time I flew over it, it only took 3 minutes to cross), it has the greatest volume: this sliver of lake holds more water than all the American Great Lakes combined. 20 per cent of the world’s (unfrozen) fresh water is here. I would not be surprised if Lake Baikal holds more than 20 per cent of the world’s fresh water biomass. In other deep lakes such as Lake Tanganyika (or even Loch Ness) only the top layer is oxygenated, and the deeper water is poisoned by hydrogen sulfide, but in Lake Baikal the habitable zone stretches all the way to the bottom, a staggering 1637 meter below the surface. A combination of heat from below and cold at the top keeps a vigorous circulation going and brings oxygen to the far deep.
Siberia is famously cold. The lake reportedly has a moderating influence over the local climate, but this can be hard to believe, seeing the sometimes meter-thick ice cover lasting from January to May. In the south, the ice disappears mid-May but in the north it lasts until early June, accompanying the flowering of the rhododendron bushland. Daytime highs are below freezing from late October until late March. In nearby Irkutsk, the record low temperature is -50C. Summers are short and rainy but pleasantly warm (rarely hot), with day time temperatures above 20C for three months. Mosquitos, however, own the summer. The summer weather can change quickly, and I can say so from experience. In Novosibirsk, to the west, I have seen the temperature drop from 30C to snow within two days. By Siberian standards, this is a mild climate. Still, even in the summer the lake is too cold for swimming. The cold water gives rise to the famous Baikal fog which can hang over the shores for much of the time especially in early summer. Perhaps this fog is at the origin of the legend of its formation at the beginning of the post. Chesterton famously wrote of the English weather But I will praise the English climate till I die, even if I die of it. One wonders what he would have made of Baikal.
The climate used to be classified as sub-arctic, but since 2000 it has warmed to such a degree that it is becoming continental. The local freezers (holes in the ground with a lid) are warming up.
Lake Baikal lies 480 meter above sea level. It is 635 kilometer long and 50-80 kilometer wide. Over 400 rivers and water courses flow into, but only one flows out: the kilometer-wide Angara, on which Irkutsk lies, 70 km away. Downstream it becomes the Yenisei river, one of the largest in Siberia and feeding the Arctic Ocean. The lake consists of three separate basins, of which the middle basin is the deepest. The southern basin is also deep, but the northern basin is much shallower. Beyond the southern end, the rift continues to the west where it is called the Tunka basin but here it lacks a lake.
South of the lake lies a steep mountain range,the Khamar-Daban range, with peaks over 2 kilometer high. This region is called the Siberian subtropics but this is either a slightly optimistic view or Russian humour. The west side of the lake is an extensive and somewhat dull plain, a never-ending field of steppe and taiga. (One of my enduring memories of Siberia is that of the beriozkas – birch trees. I stopped counting after 2 million. But I regret never making it to Lake Baikal.) East of the lake is another mountainous region, the Sayan Baikal fold belt. The north shore is also mountainous. In between, rivers have built up large and flat deltas. All the traditional Siberian landscapes are found near Lake Baikal: swamps, red bilberry, dark coniferous taiga, cedar taiga, mountain tundra, steppes and semi-desert.
In 1961, a paper mill was opened on the lake shore which became a world-famous source of pollution: the Baykalsk Paper and Pulp Mills. A town sprung up around it, called Baikalsk. After many years of protests, a water treatment facility was added but it was too expensive to operate and the plant went bankrupt shortly after, in 2009. It re-opened in 2010 with a new permit to dump untreated water into Lake Baikal, but it didn’t last long and the mill soon had to close again, this time for good.Now, 6 million tons of toxic waste are left in 13 reservoirs, and the economic mono-town of Baikalsk (a town with 41,000 people dependent on a single bankrupt employer) is in deep crisis.
People of the lake
Lake Baikal has long been at a cross roads of civilizations ever since people qualified for this term. Migrations could reach it from the west (Europe), the south (via the major river valleys around the Himalayas) and from the east. During the ice age, this area was a refuge, a place where survival was possible because of the local climate.
This skeleton of a young boy has been dated to 24,000 year ago. Its DNA shows similarity both with ancient European populations and with America: here the populations from east and west met, and mixed before moving to Beringia on the way to the invasion of Alaska. Hunter gatherers kept using the area and left their archaeological evidence, including 4000 year old cave paintings.
2200 year ago, the region found itself at the northern end of the Xiongu Mongol empire, and at that time the local tribe was called the Hunyu. It is often claimed, although not proven, that they migrated west and became the Huns. In modern days, the main population group are the Buryat, still the northernmost group of the Mongols. Whether they are related to the hunter gatherers of the previous 10,000 year is not known, but seems not unlikely.
The area around Lake Baikal became the heartland of the Mongols in the 12th century, during the time of Genghis Khan. The name ‘Genghis’, adopted later in his life, was derived from ‘tengis’ meaning ‘ocean’: it was a word used for Lake Baikal. The rest, as they say, is history, a bloody example of the ease of east-west migrations in Asia and Europe. In a much reduced form, the Mongol empire survived around Lake Baikal until the 1600’s, when it became a pawn in the struggle between the Russian empire and the rising power of the Manchu Chinese and lost its independence to both.
Many Russians have moved into the area especially since the railway provided easy access. The Buryats still live here as well, and the political persecutions of them during the Soviet Union have stopped. However, the large majority of Buryats still exist well below the poverty line.
All the people that have lived here at various times depended on the lake, for food, transport, and climate. It ruled their lives and was -and in many ways still is- something to be worshipped.
(which isn’t a word but should be.)
It began with the Siberian craton, an ancient core of a continent. In the maps, it can be recognized adjacent to the Lake, to the west. It is a fairly featureless plateau, about 500 meter above sea level. To the east is the Baikal-Patom mountain range, which was the edge of the craton and became a mountain range in the Silurian. Southeast lies the Sayan-Baikal fold belt, already mentioned, where a series of microcontinents and volcanic arcs were merged with the craton. This was always a line of weakness. It worsened with the continental collision in the mesozoic, along the Mongol-Okhotsk line: this left a series of SW-NE fault lines and fold belts. The collision is still visible in the Sea of Okhotsk. By the end of the mesozoic, the region had become stable, but here at the edge of the underlying craton, a major line of weakness had been build into the fabric of the land. Nowadays, the region east of Lake Baikal is recognised as a separate plate, the Amur plate, consisting of the arcs and platelets pasted onto Eurasia, held in place by the north China craton.
Before 30 million year ago, this was mildly elevated land. The proto-Baikal began to form 30 million year ago as a series of shallow lakes in the southern and central region, amidst the rising mountains. The lakes formed in a river bed draining from the Mongolian highlands. They left sediments which has been dated. From 10 million year ago, the lakes rapidly became deeper and the uplift in the mountains increased, still mainly in the southern and central basins but the northern basin began to grow. About 2.5 million year ago, rifting accelerated, as seen by a change in the sedimentation. This happened along the entire Baikal rift.
By 3 million year ago the rift valley had formed and the deep lakes created by the subsidence of crusta blocks in the rift. The subsidence is huge. From the peak of the surrounding mountains to the bottom of the sediment is almost 13 kilometer! The sediment filled in the hole created by the sinking crust. 9 kilometer of sediment has accrued, including large reservoirs of methane hydrates. The rift began to widen, at the present time by 5 mm per year.
Rifts and rifting
Rifts come in two varieties: wide (or diffuse) rifts and narrow rifts. An example of a wide rift is the Great Basin in the American west. It consists of numerous deep basins, together covering the region from California to Montana. An example of a narrow rift is the African rift, a narrow(ish), deep valley stretching over much of the continent. Just looking at the maps shows how different these two are. Both varieties of rift are caused by crustal extension (sides being pulled apart) but they differ in the strength of the lithosphere (the stuff just below the crust, 50-100 km deep). When the lithosphere is weak, crust stretches easily and a wide, diffuse basin develops. When the lithosphere is strong, you get a narrow, deep tear. Once the extension develops, the crust between the two sides that are being pulled apart loses support and begins to sink. Narrow rifts especially can become very deep. Baikal is clearly an example of a narrow rift.
What causes rifts to develop? That is the right question to which we don’t quite know the right answer. There will be more than one answer. In some cases, as in the Djibouti rift where the African rift and the Red Sea meet, a mantle plume seems to blame. The upwelling cracks the crust and pushes the sides apart. But in many cases there isn’t a clear hot spot associated with the rift. In the US, for instance, the Yellowstone hot spot crossed the rifts but did not affect them much, while further south the rifts are very similar but no hot spot is anywhere near. There must be more to it.
Two other processes can cause rifts. A nearby mountain range can causes faults by its weight, or a subduction zone of an oceanic plate can pull the neighbouring continental plate apart. Sometimes a rift can form in one way but change character: for example, the Azores started out when the Atlantic formed, as a propagating fault, but later hot mantle material began to come up forcing the volcanism. In this case, though, the driving force is still mainly the pull from the plates.
In the modern world, there are two main actors driving the plates. The most important is the Pacific ocean, rimmed by subduction zones. Whilst the Atlantic ocean plate is passive, the Pacific plate is the main player affecting America, the Atlantic, Europe, and Asia. The Pacific plate has achieved worldwide domination! But at the price of being subducted into oblivion. Ruling has a cost. The second actor is India, which crashed into Asia. This is only one part of the closing of the Tethys ocean which once ran from Spain to China, but India did more damage than any other part along this collision front. The two are acting together, and Siberia is in the firing line. It is in danger of breaking up.
So why did the Baikal rift form? It is, as it turns out, a complex interaction. There is a clue in when it started, 30 million year ago. This was the time when the the effects of India colliding with Asia first reached the area. This collision push into Asia and caused compression in the SW-NE direction in the Baikal area. In response, the ancient fault responded by extending in the NW-SE direction. This extension caused the shallow lakes to form in the south and central region. Later, the subduction zone near Japan had an unexpected effect. A back arc developed, causing the opening of the Sea of Japan. This back arc pushed against the eastern movement of Asia (and Europe). Thus, extension stopped. The Tibetan plateau had grown up by now and its weight renewed the push. The rift narrowed and deepened in response. Finally, the back push ceased a few million years ago. The Tibetan push now started to squeeze the Amur plate to the east, causing a counter-clockwise rotation. The Baikal rift started to widen to accommodate this movement.
The region has always been earthquake-prone, including some large ones. Geological activity has consequences. During 2015, concerns were raised because of a small swarm of M3-M5 quakes east of Baikal. This was followed by an M6 quake underneath Lake Baikal in February 2016. No damage was done, but it is a warning that this is a seismically active zone.
Lake Baikal has a history of damaging events. The largest recent major earthquake happened on 12 January 1862, estimated at M7.5, hitting the populated southeastern shore of Lake Baikal. There had been a foreshock a day earlier. The main quake was centred on Tsagan, a region adjacent to the lake with steppe, several small lakes and marshland. Reports talk about the ground moving in waves and water and sand shooting out of the ground. The ice on the lake broke and an ice and water tsunami reached the shore. Perhaps 1300 people died, mainly Buryats: the local Russian villages were at higher elevation while the Buryats lived near the shore. The Tsagan sank by 2 meter which was bad news as it was barely at lake level to begin with: it is now known as Proval Bay. 200 km2 became submerged. The area was the delta of the river Selenga (explaining why it was close to lake level), and new sediment has slowly moved the shoreline back towards the lake. The recurrence time for this region has been estimated at 1100 year. The next big earthquake should not be here.
But smaller ones could. On 29 Aug 1959, there was an M6.8 earthquake in this area. The stress in this area seems to have been relieved for now, and the next large earthquake may be further west on the fault.
There is a legend that at one time the Yakut people lived around the lake, but that they left after a number of large quakes. The olonkho (Yakut legend) runs:
The middle country trembled
Like a quaking quagmire;
The sea waves shook up;
The Baikal waves raged;
On the opposite side of the valley
Fell down cliff peaks;
The whole valley burst into lightning flame.
Rifts should be full of volcanoes. Look at the African Rift, flanked by impressive volcanoes, or the Icelandic rift. But it is not that simple. An active rift, pushed apart by rising mantle material, will suffer a bad case of volcanistrics. But a passive rift, pulled apart by the movement of distant plates, is more or less immune to volcano-enza. Baikal, being a passive rift, lacks volcanoes.
Hot springs are present, and are in fact one reason for the freshness of the water. They keep the water moving and prevent de-oxygenated layers to occur. Many other lakes could learn from this. But hot springs do not volcanoes make.
There are volcanic fields around the Baikal rift. At the eastern end of the northern Baikal rift, several hundred kilometer east of the northern tip of Lake Baikal, lies the Udokan plateau, where volcanism began 14 million year ago and some activity may have been recent, perhaps even in the Holocene. Closer to the Lake, 200 km east of the central region is the Vitim plateau, larger than Udokan. It contains a large number of cinder cones and lava fields, some of which are recent but there is no indication that activity is still continuing. A third region is in Tunka, the western extension of the Baikal rift. This is called the Oka plateau or Jom-Bolok, and is currently the most active although it contains only four volcanic peaks A large lava flow, 8 km3, was formed in the early Holocene, perhaps 7000BC. The most recent (much smaller) flow is less than 3000 year old.
To what degree these volcanic fields are related to the Baikal rift is not clear. They could also be the northernmost extent of the Himalayan activity. But the main volcanics may still be in the future. If the Baikal rift continues to wide it will allow mantle magma to penetrate the lithosphere. Eventually a spreading ridge could form, and a new ocean. A passive rift can grow to be an active one.
Will this happen here? It could. The nearby subduction zone beyond Japan, combined with India’s split, could tear Siberia in two. If that happens, far from all the continents coming together again in a future supercontinent, the Earth 6th ocean would form. The Baikal Rift follows an old suture at the edge of an even older craton. A new split would likely re-open this weakness, between Baikal and the Sea of Okhotsk separating Eurasia from Mongolia and China; the latter slowly migrating towards America, closing the North Pacific in the process. What a world it would be.
So the true volcanic activity may still be in the future. The spreading accelerated a few million year ago. The rate is still low, but the situation is fluent. If the break happens, one could expect volcanoes to form along the edges of the break. Just wait and see.
Life as we know it
The lake has a huge range of life forms which occur nowhere else on earth. It may not be as visually spectacular as a tropical reef, but the numbers are impressive. Over 800 endemic animals species have been reported, including 27 species of fish. Many of the endemic animals are species of tiny shrimp. There are also 14 endemic types of sponges and 180 different molluscs.
Best known are the seals. There are some 60,000 Nerpa seals in the lake, a rare group of freshwater seals. Their presence show how biologically productive the lake must be. The main food comes from the endemic fish species, namely two species of golomyanka, translucent but fatty. The golomyanka (the Baikal oilfish) are the most numerous fish in the lake, accounting for 67 per cent of the total fish biomass. In the summer, the seals tend to stay in the northern part. At other times, they are everywhere. Over winter they keep breathing holes open in the thick ice, and their thickly furred white young are born on the ice nearby.
How did the Nerpa seals get here? They are not known for traveling over land, and Baikal is very far from the nearest ocean. Lake Baikal is old, and sometime since its beginning 30 million year ago, the seals were able to reach here and gave it a strong seal of approval. Even today they are sometimes seen in the Angara river, although unable to get past the dams. Their nearest genetic relatives live in the Arctic Ocean. Did the Arctic ocean reach here? Unlikely, given that the region is 500 meter above seal level, but at times huge lakes flooded parts of Siberia which may have helped. In the end the seals must have managed to travel up the Lena and Yenisei rivers. Genetic evidence puts this at some 4 million year ago. As mammals, dealing with the change from salt to fresh water would not have presented evolutionary problems – there are other fresh water seals in the world, although none as isolated as the Nerpa.
Lake Baikal is one of the geological wonders of the world. The climate is not conducive for tourism but maybe that has helped to protect it. The crystal clear water has to be seen to be believed. The mountain scenery is impressive, and the taiga in spite of its stark uniformity has a beauty of its own. Yet Baikal is also a place that could shape the world. It feels its way around an inherited weakness in the continent and may yet break it. If it does, the volcanoes will be the first sign of a change of direction of the continents. The next supercontinent would be delayed, and assembled differently. What a difference a lake can make.