volcanoes at hotspots

continental hotspots

The hotspots that are known beneath continents are extremely large. The reason is that it takes a massive mantle plume to generate enough heat to penetrate through the relatively thick continental crust. The eruptions that come from these hotspots are infrequent but massive, often felsic and explosive. All thats left at Yellowstone at the moment is a giant caldera and a very hot spot beneath.

pacific hotspots

The South Pacific has many hotspot volcanic chains. The hotspot is beneath the youngest volcano in the chain and older volcanoes are found to the northwest. A volcano forms above the hotspot, but as the Pacific Plate moves, that volcano moves off the hotspot. Without its source of volcanism, it no longer erupts. The crust gets cooler and the volcano erodes. The result is a chain of volcanoes and seamounts trending northwest from the hotspot. Prominent hotspots of the world. (a) The Society Islands formed above a hotspot that is now beneath Mehetia and two submarine volcanoes. (b) The satellite image shows how the islands become smaller and coral reefs became more developed as the volcanoes move off the hotspot and grow older. The most famous example of a hotspot in the oceans is the Hawaiian Islands. Forming above the hotspot are massive shield volcanoes that together create the islands. The lavas are mafic and have low viscosity. These lavas produce beautiful ropy flows of pahoehoe and clinkery flows of aa, which will be described in more detail in Effusive Eruptions.

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hotspot versus island arc volcanoes

How would you be able to tell hotspot volcanoes from island arc volcanoes? At island arcs, the volcanoes are all about the same age. By contrast, at hotspots the volcanoes are youngest at one end of the chain and oldest at the other. Click image to the left or use the URL below. URL:

intraplate volcanoes

Although most volcanoes are found at convergent or divergent plate boundaries, intraplate volcanoes may be found in the middle of a tectonic plate. These volcanoes rise at a hotspot above a mantle plume. Melting at a hotspot is due to pressure release as the plume rises through the mantle. Earth is home to about 50 known hotspots. Most of these are in the oceans because they are better able to penetrate oceanic lithosphere to create volcanoes. But there are some large ones in the continents. Yellowstone is a good example of a mantle plume erupting within a continent.

instructional diagrams

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questions

hotspot volcanoes are made by ____.

a) two plates converging

b) two plates diverging

c) two plates moving past each other in opposite directions

-->  d) a plate moving over a mantle plume

lava made by hotspot volcanoes makes this type of volcano.

-->  a) shield volcanoes

b) cinder cone volcanoes

c) composite volcanoes

d) none of the above

the hawaii hotspot creates

a) massive shield volcanoes.

b) felsic lavas.

c) lavas with low viscosity.

-->  d) both a and c.

hawaii is the only hotspot volcano chain in oceanic crust.

a) true

-->  b) false

most hotspots are located beneath continental crust, like yellowstone.

a) true

-->  b) false

eruptions of hotspots beneath continents are extremely explosive because

a) the eruptions occur frequently.

b) the eruptions release enormous amounts of felsic lava.

-->  c) a massive plume massive enough to penetrate continental crust is very hot.

d) both a and c.

you know that a chain of volcanoes formed at a hotspot rather than due to subduction if

-->  a) the volcanoes are oldest at one end and youngest at the other.

b) the volcanoes are all about the same ages.

c) the volcanoes are composite volcanoes rather than shield volcanoes.

d) both a and c

yellowstone is a mantle plume that has erupted within a continent.

-->  a) true

b) false

how does melting take place at a mantle plume?

a) added heat to raise the temperature.

-->  b) pressure release to lower the melting temperature.

c) added water to lower the melting temperature.

d) both a and c

why do older volcanoes that formed at hotspots get smaller and eventually sink beneath the sea?

a) erosion

b) end of eruptions

c) sinking of crust as it cools

-->  d) all of the above

diagram questions

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