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9 Cards in this Set
- Front
- Back
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According to Andersons theory of dykes how do the form? |
Dikes form preferentially perpendicular to s3, the least compressive principal stres |
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What are the 3 types of Dykes |
Radial, conesheet and ring |
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How do radial and conesheet dykes form? |
Form as a magma body expands during multiple events |
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How does a Ring dyke form |
From a single event of a collapse above the magma chamber - which forces out a ring of magma |
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Compare and contrast ring dyke and conesheet |
Conesheet- cm-m wide dips inward at base Ring dykes- m -Km may be vertical or dip outward |
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What types of Caldera are there? |
Lake calderas, Pit craters and resurgent |
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What type of caldera would be on a moderate sized stratovolcano? |
As stratovolcanoes have violent eruptions- lake caldera- deep and steepsided walls caused by collapse of land above magma chamber due to explosive eruption up to 10 km wide? |
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Whta type of caldera is typical for shield volcano ? |
gentle effusive eruptions would leave pit craters 1-5km wide that may overlap as collapse is gentle and gradual |
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What is the largest caldera type? |
Resurgent caldera e.g. Toba, they can be 15 to 100 kmwide broad topographic depression with a raised central mass. Not seen an eruption this size in historical time |
