A Perfect Planet
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- Episode
- Episode 1 - Volcano
- Broadcast Info
- 2021 (58 mins)
- Description
- Without volcanoes life on Planet Earth would never have got started. They are responsible for both our breathable atmosphere and the oceans. They are also the architects of the planet, with over eighty per cent of the Earth’s surface being the result of magma bursting up from the molten interior - providing a platform for life. And with around fifteen hundred currently active volcanoes on land alone, like Kilauea on Hawaii, it’s work that never stops. Volcanoes are undeniably destructive but even the most formidable can support life. Ol Donyo Lengai, in Tanzania, is one of Africa’s most active volcanoes yet it’s responsible for, perhaps, the continent’s greatest natural history spectacle. Sitting on Lengai’s northern flank and fed by a concentration of chemicals from the volcano, Lake Natron is one of the world’s most corrosive bodies of water but, when conditions are right, it becomes a focal point for two million lesser flamingos, who come to the lake to breed. Nesting in the dry centre, the flamingos’newly hatched chicks are safe from land predators by a moat of caustic soda. It’s only when the chicks begin their epic trek to freshwater springs at the edge of the lake that their challenges really begin. Female land iguanas, in the Galapagos, also take advantage of what volcanoes have to offer. Every year, up to 2,000 of these metre long lizards, all heavy with eggs, make the ten day trek from the coast to the top of La Cumbre, Fernandina Island’s active volcano, from where they descend the precipitous slopes to the crater floor. Once at the bottom, they lay their eggs in the soft, warm ash, which is the perfect temperature for incubating their eggs. Volcanic islands make up just five per cent of the planet’s land but they are home to nearly twenty per cent of its species. Cut off from their mainland relatives - and faced with a whole range of new challenges - animals often evolve very quickly on islands: sometimes in truly bizarre ways. On the tiny island of Wolf, in the Galapagos, a group of castaway finches have overcome the challenges of a limited supply of food and water by exploiting a completely un-finch-like diet. They have learnt to feed on the blood of the seabirds that roost and breed on the island. It’s an adaptation that has turned them into Galapagos’s newest bird species - the vampire finch. Volcanic islands don’t last forever, but even when the forces of erosion wear them down many morph into a new kind of habitat. As the land disappears beneath the waves, coral continues to grow up around the shore and with changing sea levels eventually all that’s left is a lagoon surrounded by a coral reef - an atoll. Aldabra, in the Indian Ocean, is one of the world’s largest atolls and it’s now home to one hundred thousand giant tortoises. Able to go without food and water for long periods of time, this extremely remote and uninhabited ring of land is the perfect refuge for these lumbering giants - except for one thing, the midday sun. So, every day as the temperature rises they move en masse, seeking shade under trees and in caves in the coral rock. Volcanic hotspots are also the source of powerful thermal activity at the surface. Yellowstone, in the centre of North America, sits on top of a vast, dormant volcano but not far below ground there is still magma and that heats the ground water to boiling point. The result - geysers, some bursting out to heights of up to ninety metres. Thermally heated springs also keep some of Yellowstone’s rivers running even during the coldest winters - enabling river otters to fish year round. It’s a similar story in the Valley of the Geysers, in Russia’s Kamchatka. When the rest of Kamchatka is covered in snow, this valley remains green and ice free providing much needed forage for bears fresh out of hibernation. Kamchatka’s bears also have the region’s volcanoes to thank for another vital source of food. Every year, millions of spawning salmon come to Kurile Lake to spawn and it attracts the greatest assembly of brown bears found anywhere on the planet. The lake’s water has been fertilised by mineral rich ash from regular volcanic eruptions and this provides the salmon’s newly hatched young with abundant food - hence the huge shoals of fish. But it’s not just in Kamchatka, our entire planet depends on minerals brought up from Earth’s molten core. A single ash cloud can carry billions of tonnes of minerals, which is why lands surrounding volcanoes are some of the world’s most fertile - and no more so that the Serengeti in Tanzania. These mineral rich grasslands support the greatest gathering of herbivores and predators on the planet. Volcanoes are the planet’s most powerful force - and the most dangerous. Several times in the Earth’s four billion year history, out of control volcanic activity has brought about a major change in our atmosphere - through the release of carbon dioxide - resulting in mass extinctions. Yet, as this episode reveals there would be no life without them and for the last ten thousand years the amount of carbon they have released has kept our planet stable and warm. Today, we have much more to worry about from the human force as our activity currently emits more carbon dioxide into the atmosphere than all the world volcanoes combined.
- Genre
- Geology; Natural History; Vulcanology
How to cite this record
The Open University, "A Perfect Planet". https://learningonscreen.ac.uk/ou/search/index.php/prog/237963 (Accessed 10 Jan 2025)