Download Classroom Space Volcano!

Classroom Space
Volcano!
Teacher’s Answers
The Position of Volcanoes on the
Earth and Mars.
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Most of the volcanoes are found along plate boundaries (at spreading centres or
subduction zones). They are mostly found here because magma can easily get to the
surface as the plates move away from one another, or as one plate moves beneath the
other. Some volcanoes can also be seen over mantle hotspots e.g. Hawaii or the Canary
Islands.
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The term ‘Ring of Fire’ refers to the fact that there are volcanoes in a near circular
arrangement surrounding the Pacific. These volcanoes occur along the margins of the
Pacific plate. The ‘fire’ is obviously a reference to lava!
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Japan
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Earthquakes
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Earthquakes and volcanoes occur along plate boundaries – where two plates are moving
against each other. The most powerful earthquakes are found along transform fault
margins and convergent margins.
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Great Britain is far from any plate margins, and is not over a hotspot area; therefore it
has no active volcanism.
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If the plates move a couple of centimetres a year, then hundred of millions of years ago
the plates would have been thousands of kilometres away from the positions that they are
in today. Therefore, at that point in history, Great Britain could have been over a hotspot
or nearer to a plate margin.
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Volcanoes can only occur when there is molten rock (magma) that can reach the surface.
This can happen at a plate boundary where the plates are diverging (moving away from
each other) and the resulting gap allows magma to reach the surface. Or if the denser
oceanic plate sinks below the continental plate in a subduction zone and that oceanic crust
becomes molten, and the resulting high pressures enable it to be forced to the surface.
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There are lots more volcanoes on the Earth than on Mars.
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There are two few volcanoes on Mars to be able to make out a pattern for sure, but the
fact that they appear in clumps, combined with the fact that there are no ‘marsquakes’ on
the planet, would suggest that they occur over hotspots.
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The evidence suggests that the surface of Mars is not divided into plates. If the volcanoes
occur over hotspots and there are no ‘marsquakes’, then there are likely to be no plate
boundaries. The map appears not to be divided into ‘continents’, and there is no evidence
that any pieces would have fit together as the continents on Earth did in the past. Also
the land in the entire northern hemisphere is very different to that in the south.
The Position of Volcanoes on the Earth and Mars – Teacher’s Answers
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Classroom Space
Volcano!
Teacher’s Answers
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The cratered uplands are the oldest – the heavy cratering suggests that this surface was
around during periods of heavy bombardment by comets, asteroids and meteorites which
stopped around 3.5 billion years ago. If the northern hemisphere was indeed impacted by
a giant object, the surface would have become molten and the rock would have solidified
and essentially been created again as new.
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Any large craters in the Northern hemisphere would have been ‘melted away’ by the heat
of the giant impact. There are some smaller craters in the northern hemisphere and these
were made after the end of the period of heavy bombardment.
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The lava flows are relatively young and continued to flow long after the periods of heavy
bombardment (after 3.5 billion years ago), therefore each new lava flow created new
igneous rock and erased any surface features that previously existed. Again there will be
some small craters on the lava flows.
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Yes the rock on each planet will be similar if the planets themselves are made of similar
material. This is quite likely as they evolved from the same material when the solar
system was formed and they are both terrestrial (rocky) planets.
The Position of Volcanoes on the Earth and Mars – Teacher’s Answers
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