Revising Geology #9

IGNEOUS STRUCTURES

The igneous structures usually included in exam questions are: plutons, dykes, sills, lavas. They may feature in the written exams, but also in mapwork questions.

a. How can you recognise each of these in the field or on a map, and distinguish between them? Use

  • grain size
  • massive or sheet-like
  • nature of the contact between the igneous rock with the country rock
  • relationship between the structure of the igneous feature and the bedding of the country rock.

Make up a chart which summarises these points.
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Exam technique #9

More about mathematical Geology questions.

1. Instructions given in the question stem.

Estimate …
Give a sensible approximation or order of magnitude – no need to reach for your calculator. Note – an estimate is not a guess!

Measure …
Use a ruler or protractor to get an accurate result! If you are NOT accurate, you WILL lose marks.

You must bring a decent ruler (preferably 30cms long) and a protractor to all Geology exams.

Calculate …
Work out the exact answer from the information given.

  • you must show your working!
  • show the units, if not given already.

Check your answer. Does it agree with your initial estimate?

Determine …
Similar to ‘calculate’, using known values and a standard formula.
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