BAC1 tech · Biology, Geology and Environmental Sciences
Earth dynamics · The geosphere
Magmatism and igneous rocks
A volcano is simply the surface outlet of a process that begins much earlier, deep underground: a solid rock melts, a magma rises and a new rock forms as it cools. The tectonic setting in which each step takes place determines what kind of magma, volcano and rock result.
Before you start, make sure you know: Plate tectonics (4th ESO)
The Earth's mantle is at temperatures of over $1000\text{ }^\circ\mathrm{C}$ and yet it is almost entirely solid because of the tremendous pressure it is under; even so, in certain places molten liquid rock wells up. Under what precise physical conditions can a solid rock deep underground cross the threshold and melt?
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Define magma and explain the three factors that can cause rock inside the planet to melt: an increase in temperature, a decrease in pressure, and the addition of water.
Define magma and explain the three factors that can cause rock inside the planet to melt: an increase in temperature, a decrease in pressure, and the addition of water.
At ridges, magma is generated by decompression melting, and at subduction zones by the addition of water. Explain what each mechanism consists of and discuss why the…
At ridges, magma is generated by decompression melting, and at subduction zones by the addition of water. Explain what each mechanism consists of and discuss why the water released by the sunken plate melts the mantle above it even though the temperature does not rise.
If you collect lava samples at the Mid-Atlantic Ridge, in the Chilean Andes and in the Canary Islands, you will find that their density, colour and chemical composition are completely different. Why does plate tectonics fundamentally determine the composition of the magma and the type of rock that forms?
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Explain why most of the planet's active volcanoes are aligned with lithospheric plate boundaries, and cite a volcanic region associated with a divergent boundary and…
Explain why most of the planet's active volcanoes are aligned with lithospheric plate boundaries, and cite a volcanic region associated with a divergent boundary and another with a convergent boundary.
Match each magmatic setting — mid-ocean ridge, subduction zone, and hotspot — with the type of igneous rocks it produces, choosing between basic rocks (basalt, gabbro)…
Match each magmatic setting — mid-ocean ridge, subduction zone, and hotspot — with the type of igneous rocks it produces, choosing between basic rocks (basalt, gabbro) and intermediate or felsic rocks (andesite, granite), and cite a famous archipelago formed by a hotspot.
Distinguish between magma and lava, and between plutonic (intrusive) and volcanic (extrusive) rock, giving an example of each rock and explaining where each one cools.
Distinguish between magma and lava, and between plutonic (intrusive) and volcanic (extrusive) rock, giving an example of each rock and explaining where each one cools.
In 2018, the lava from Kilauea (Hawaii) advanced like a river that could be approached without immediate danger of an explosion, whereas in 1980 Mount St Helens blew away half a mountainside in seconds. What physical property of magma determines whether a volcano pours out calm rivers or bursts in an explosive catastrophe?
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Explain what the viscosity of a magma is, which three factors it depends on (silica content, temperature and dissolved gases) and how viscosity influences whether an…
Explain what the viscosity of a magma is, which three factors it depends on (silica content, temperature and dissolved gases) and how viscosity influences whether an eruption is gentle or explosive.
Name the three major groups of products a volcano emits (lava flows, pyroclasts and gases) and associate a specific risk for nearby populations with each one.
Name the three major groups of products a volcano emits (lava flows, pyroclasts and gases) and associate a specific risk for nearby populations with each one.
Distinguish between a stratovolcano and a shield volcano: the shape of the edifice, the composition and viscosity of their lavas, the dominant type of eruption and an…
Distinguish between a stratovolcano and a shield volcano: the shape of the edifice, the composition and viscosity of their lavas, the dominant type of eruption and an example of each (Teide or Vesuvius versus Hawaii).
What is a volcanic caldera and how does it form? Distinguish it from a crater and name an example in Spain or in the world (Las Cañadas del Teide, Santorini,…
What is a volcanic caldera and how does it form? Distinguish it from a crater and name an example in Spain or in the world (Las Cañadas del Teide, Santorini, Yellowstone).
Explain what the volcanic explosivity index (VEI) measures, which parameters it is calculated from (volume of material emitted, height of the eruptive column) and why it…
Explain what the volcanic explosivity index (VEI) measures, which parameters it is calculated from (volume of material emitted, height of the eruptive column) and why it is an open scale similar to the earthquake magnitude scale.
In 2021, the lava from the Tajogaite volcano entered the sea and built a new lava delta. Describe the processes that occur when lava comes into contact with ocean water…
In 2021, the lava from the Tajogaite volcano entered the sea and built a new lava delta. Describe the processes that occur when lava comes into contact with ocean water (sudden cooling, clouds of acidic vapour, fragmentation) and the added risks for the population and for fishing.