I’ve decided to stick with the theme for this week.
- Little Ice Age – there was heightened volcanic activity during the Little Ice Age, from the 16th-19th centuries. It certainly contributed to the cold weather, because ash and chemicals from eruptions blocks and reflects sunlight and has a noticeable cooling effect. However they could have both been caused by something else.
- Vesuvius – Mt Vesuvius erupted in AD 79 burying Pompeii. It seems that there were foreshocks for several years, however the eruption itself caught people by surprise, which is why they have been preserved beautifully. Most of the people who died actually suffocated because of the poisonous gases from the volcano, not from being buried in the ash.
- Olympus Mons – on Mars, probably the solar system’s largest volcano it is 550km wide and 21km high. It is so large because Mars does not have tectonic activity, the crust has remained over a hot spot for millions of years and the volcano has grown through many eruptions.
- Io – the most geologically active body in the solar system. It is the closest of the four Galilean (large) moons of Jupiter and is so active because of its elliptical orbit. As it gets closer and further away from Jupiter gravity pulls it and forms changing tidal bulges, the movement causes friction which creates heat. The volcanoes shoot out sulfur and sulfur dioxide, some of which escapes the moon and drifts to its sister moons. It has mountains taller than Mt Everest.
- Lunar maria – these are not strictly volcanoes, but they are volcanic in origin. They are the large flat structures we can see that make up the face/rabbit/man in the moon. Mare is latin for sea. They are only found on the face we see – the far side is mountainous. The earth’s gravity has pulled the radio-active elements that produce heat closer to our side of the moon, and in the past enormous basaltic lava flows covered a large part of the near surface. This lava solidified into the dark, flat maria.
- Kimberley diamonds – over a billion years ago the Kimberley in northern Western Australia was not attached to the same continent, but sat on a different tectonic plate. When it collided with what would later become Australia, there was intense volcanic and earthquake activity, as there is today at plate margins. The diamonds come from a volcanic pipe, the result of an immense eruption from a deep volcano, at least 3 times as deep as other volcanoes.
- Hawaii – the Hawaiian archipelago shows the gradual drift of the tectonic plate it rides on. Deep in the earth is a hot spot, as the Pacific plate drifts northwest new volcanoes are formed by the rising magma. As the northern islands are the oldest volcanoes, they have been eroded the most and are the smallest islands. Even further northwest are the older volcanoes that no longer reach the surface, the chain of the Emporer Seamounts. The islands themselves are only the tips of the volcanoes, most is underwater.
- A’a and Pahoehoe – there are three main types of lava, two are named with Hawaiian words a’a and pahoehoe. A’a (uh-uh) is stony, rough lava and is around 1000-1100 degrees C. Pahoehoe (p-hoi-hoi) is smoother and flows more, it is usually around 1100-1200 degrees C. The third type of lava is pillow lava, and usually forms under water or ice.
- Pele’s tears – Pele is a Hawaiian fire goddess (are we sensing a theme here?) and Pele’s tears are solidified droplets of volcanic glass, formed when they are shot into the air and solidiy. There is also Pele’s hair, formed when long thin strands of lava are whipped about by the wind, and Pele’s seaweed (limu o Pele), formed when water touches lava and instantly boils, forming bubbles.
- Krakatoa – is a volcanic Indonesian island in the Sunda straight. When it erupted in 1883 it was one of the biggest eruptions in recorded history, the explosion was heard in Perth, WA, 3110 km away and Rodrigues near Mauritius, 5000km away. The eruption was caused by sea water getting into the incredibly hot magma chamber, it boiled instantly but was contained by the chamber, hence the explosion. It was the equivalent of 13000 of the bombs dropped on Hiroshima.
- Tambora – An active volcano in Indonesia, near Krakatoa where the Australian and Asian tectonic plates meet. Its eruption in 1815 is considered the largest volcanic eruption in recorded history and also the deadliest, with a death toll of at least 71,000 people. There was so much dust and gases put into the atmosphere that it blocked and reflected sunlight, causing the temperature in the northern hemisphere to drop by 0.5 degrees and ‘the year without a summer.’ The extreme cold disrupted harvests and killed livestock, leading to widespread famine.
- Deccan Traps – the Deccan traps in India are one of the largest volcanic features on earth. They formed between 60-68 million years ago, but may have taken as little as 30,000 years. They are estimated to have been half the size of modern India, although they are smaller today. They were most probably formed by the Reunion mantle plume when India was close to Africa. The amount of poisonous gases released and the resulting drop in temperature of up to 2 degrees C would have been a major stressor on life and could have contributed to the mass extinction that killed the dinosaurs.
- Eyjafjallajökull and Katla – these are two volcanoes in Iceland covered by glaciers. They are linked, eruptions in Eyjafjallajökull usually mean an eruption is coming in Katla. Katla is dangerous because eruptions melt the glacier and cause enormous floods, and it is thought to be responsible for 6-7 cubic kilometres of volcanic ash from 10,600 years ago. An eruption of this size could halt air travel for years as the dust is carried around the world and have a major effect on climate. Katla usually erupts every 40-80 years, but has not had a major eruption since 1918 with minor eruptions in 1955 and 1999. Now that Eyjafjallajökull has erupted it is expected to erupt ‘when’, not ‘if.’
The purpose of the meme is to get to know everyone who participates a little bit better every Thursday. Visiting fellow Thirteeners is encouraged! If you participate, leave the link to your Thirteen in others’ comments. It’s easy, and fun!
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