From Earth Science On-Site
The Ercall, Shropshire
KEY STAGE 3 TEACHERS' NOTES
© GeoconservationUK ESO-S Project, 2017
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KS3 Homework answer sheet Ercall Quarries
- Where in the quarries did you see an igneous rock? What did it look like? Draw a sketch if it helps.
The rock was the pink granophyre found in quarry 1. The crystals in it are all the same size and there are two sorts of crystals, a grey one called quartz and a pink one called feldspar.
- In the quarries you saw two sedimentary rocks. What are they called? What did they look like? Draw sketches if they help you to explain
At locality “C” in quarry 2 there was a grey rock called quartzite, which had medium sized grains of quartz in it. It formed thick beds of rock with few joints in it.
At locality “E” between quarries 1 and 2 there was a grey rock called conglomerate. It was made up from small pieces of other rocks, some, quite rare, from the granophyre (red/pink), and some from a rock called rhyolite (striped). This rhyolite is the oldest rock in the Ercall quarries as dated by radio isotope methods.
- What evidence have you seen for erosion taking place now in the quarries?
In quarry two on the left side there are scree slopes where fragments of rock are breaking off (and also in quarry one where the granophyre is exposed). This is one of the reasons for the warning signs.
- What evidence is there that erosion took place in the distant past? (Hint: think about where one type of rock lies on top of another type.)
At locality “E” the conglomerate is lying on top of the granophyre. The top surface of the granophyre is uneven which means that it was being worn away before the conglomerate was deposited on it, but also the conglomerate has rare pieces of granophyre in it (which are quite difficult to find) and which must have been eroded from the rocks below.
Teachers’ are reminded to refer to Briefing Notes for additional field information.
Answer for Pupil Worksheet for Locality “B”
Answer for Pupil Worksheet for Localities “C” & “E”
Reading the clues in the sedimentary rocks
Answer for Pupil Worksheet for site “D”
||Put a tick to show the word(s) that describe the ripples
|Shape of ripples in cross section:
|Shape of ripples over the crest:
|Shape along the crest:
||roughly straight/ parallel?
roughly straight/ parallel but splitting?
||Write your measurement here (in mm)
|Calculation of the ripple index (R.I.)
||Write your working here
RI >17 suggests wind formed ripples
RI<15 suggests water formed ripples
|170 / 15 = 11.33
Answer for Pupil Worksheet for Locality “E”, Activity 2
This field sketch shows the view looking towards the north east at M.R. SJ 644096
- Complete the scale on this field sketch.
- Label the following on the field sketch:
- Bedding plane
- Sandstone layer (in Wrekin Quartzite)
- Pebbles in conglomerate layer (in Wrekin Quartzite)
- Part of the unconformity between the granophyre and the Wrekin Quartzite is shown. Complete the sketch to show the rest of the unconformity.
Note: The pupils may produce a slightly different final drawing showing where the unconformity lies, but they may be right! The key point is that they identify an uneven / irregular boundary between the two rock types.
Answer for Pupil Worksheet for Locality “F”
||When it was formed
||How it was formed
||540 million years ago.
In the Cambrian Period.
|From sand & gravel deposited on the sea floor.
||560 million years ago.
In the Precambrian Era.
In an igneous intrusion.