Sedimentary rocks are important because
- they make up much of the surface of the crust
- they contain information about the history of the earth – the conditions of deposition
- they provide raw materials for industry, building etc
What does the classification of sedimentary rocks tell you about their mode of formation?
Write a 12-word description of clastic sedimentary rocks which says how they formed and how they were formed.
Write a 12-word description of calcareous sedimentary rocks which says how they formed and how they were formed.
Write a 12-word description of evaporite deposits which says how they formed and how they were formed.
Compile a chart which compares the typical features of sedimentary rocks compared with igneous and metamorphic rocks.
How would you recognise a sedimentary rock
- in the field?
- on a geology map?
DIAGRAMS IN GEOLOGY
Diagrams are very important in Geology – from fieldwork to working with maps (which are of course sophisticated diagrams). They give a visual description of the information you are trying to put into words. In exams, they can save a lot of time. Drawing diagrams is a skill which it is well worth perfecting, Yet many candidates seem to treat diagrams as unimportant – and lose marks accordingly.
The keywords are:
- compass directions
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.