3 Barnt Green Road Quarry

Barnt Green Road Quarry

Looking at the diagram you can see that from the Visitor Centre you have crossed the Lickey Hills ridge and climbed down to the Barnt Green Road Quarry.

The brown dashed lines on the diagram mark the location of faults in the rock. You can see that the ridge of the Lickey Hills is bounded by a fault along both its western and eastern edge. The eastern fault runs beneath Barnt Green Road.

 

Roads and Reservoirs

The strong hard Lickey Quartzite from the Barnt Green Road Quarry was used in the construction of roads and the Frankley Reservoir, which receives water from Wales via the Elan aqueduct.

The Frankley Reservoir built in 1904 holds 900,000 cubic metres of drinking water for Birmingham.\n\nIt did leak 540 litres per second until the fault was detected and put right in 1987.

 

Lickey Champions

This big quarry is well over 100 years old – it was worked for stone in the 19th century and closed in the 1920s. For nearly a century the quarry was abandoned and debris built up, covering the rock face. In 2010 a team of local volunteers called the Lickey Earth Heritage Champions dug out the quarry and exposed the impressive rock face again.

Even the Fire Service was involved at one point to wash the rock face using high pressure water jets. Volunteer groups like the Lickey Earth Heritage Champions play a vital role in keeping quarries like this clear and clean so that people may use them as ‘windows’ into the deep time of our planet.

Lickey Quartzite up-close

Pick up a clean piece of loose stone.
What colour is it?
How hard is it?
Look closely (with a magnifying glass if you have one) at the grains the rock is made of.

See if you agree with what a geologist would say about this rock (the following text – in the app this is not visible until user selects the ‘+’ button.

The rock has a pink-brown colour.
The rock is very hard.
It is made up of small rounded grains.
These grains are the mineral quartz. The grains are cemented together by more quartz to produce this very hard rock, which is now called quartzite.

Quartz is one of the hardest minerals. For the grains to become rounded they would need to have been rolled around or knocked against each other for a long time. Can you think of an environment in which that is likely to happen?

 

Rock beds

Scientists think that the Lickey Quartzite probably started out as sand on a sea shore some 480 million years ago. The rock is made of quartz sand grains, or sediment, laid down layer upon layer on the shallow sea floor, so it formed as a sedimentary rock. The layers in a sedimentary rock are called beds and when the sediment first settles, the beds are mostly horizontal. Look at the rock face in front of you. Can you see layers or beds of rock? Are they horizontal – or vertical – or sloping in various directions? We will think about this later.

How did seaside sand become such a hard rock? Over millions of years, the beds of sand that were deposited on the sea floor, were buried by later sediments, compressing the sand beds into rock. At some time during this process, liquids filtering through the beds of sand deposited the mineral quartz from solution to act as ‘glue’ or silica cement between the grains. The rock would have been called a sandstone at this point. Later, buried deep in the earth, the rock was subject to heat and pressure, which recrystallized the quartz grains and silica cement, binding the rock even more solidly together. In this form it is called quartzite.

Below, a cross-section showing beds of sediment accumulating.

 

Volcanoes nearby

Look at the south end of the quarry (the quarry face to your left). Notice that the beds here are thinner than elsewhere and between them, there are very thin, darker, purple-grey layers. These thin layers are rich in clay (the wet muddy layer in the picture below). It is thought, although not confirmed, that the clay may have formed from volcanic ash that every so often exploded from a volcano some distance away, and spread out in the atmosphere, then rained down here as the Lickey Quartzite was forming.

Ancient beach

A reconstruction of what geologists think this area may have looked like when the Lickey Quartzite was being deposited as beach sand, or at least as deposits just out under shallow sea water.

The key things are: There appears to have been low lying land to the east, called the Midland Platform which was part of a small continent called Avalonia. This area was along the western coastline of the Midland Platform. The sea here was shallow, but became deeper to the west, into an ocean name Iapetus (not the Atlantic of today).

480 million years ago

The Iapetus Ocean plate was gradually being pushed down under (subducted) beneath Avalonia which was moving northward. This plate subduction is why there was volcanic activity not too far away. At that time this area was around 55 degrees south of the equator. A location today that would give cold conditions, but around 480 million years ago the Earth’s climate seems to have been much warmer. So the sea here was probably quite warm!

At the time the Lickey Quartzite was being deposited, the future Scotland and northern parts of Ireland were on the opposite side of the Iapetus Ocean as part of the large Laurentian plate.

Eventually, when the Iapetus Ocean had all been subducted, Avalonia collided with Laurentia to the north-west. Rocks were deformed as a huge mountain range was pushed upwards, similar in scale to the Himalayas of today. The mountains of Scotland, the Lake District and north Wales are a remnant of this.

 

Colliding continents

Look at the quarry face again. Something very dramatic has clearly happened to the once-horizontal beds of sedimentary rock.
The image below highlights the folding.

When there are major earth movements, such as when tectonic plates collide, the effect is seen over very large areas, even hundreds of kilometres away. The pressure from two plates colliding is so great that it can squeeze horizontal beds of rock until they buckle and fold, just as you can see here in the quarry.

Creating the fold

When rock beds form they will be horizontal. But when the beds are buried under, perhaps kilometres of other rocks, then subject to the great tectonic forces produced when plates collide, the rock beds will bend into folds. When the forces are very large, or last along time, the beds will fold over on themselves. This is what has happened to the rock beds in this quarry.

 

 

Task Site 3 Questions

The stone from this quarry was used to build roads and for the dam at Frankley Reservoir. What do you think was the main reason why this stone was chosen for these purposes? Because it is:

a) A nice colour
b) Very hard
c) Rather soft and breaks easily
d) Insoluble in water

 

If you look closely at a piece of clean stone from the quarry, what mineral are the grains in the rock made of?

a) Quartz
b) Calcite
c) Haematite
d) Feldspar

 

Use the app (touch the globe under ‘then’) to find out where on the planet this area was when the Lickey Quartzite was laid down

a) At the equator
b) 55 degrees south of the equator
c) Near to the North Pole
d) 30 degrees north of the equator

 

Find out what the temperature was like at the time the Lickey Quartzite was forming around 480 million years ago

a) Below freezing
b) 1 to 10 degrees Celcius
c) 11 to 30 degrees Celcius
d) Over 40 degrees Celcius

 

What animal or plant group would NOT have been present at the time the Lickey Quartzite was forming around 480 million years ago?

a) Dinosaurs
b) Trilobites
c) Brachipods
d) Sea lilies (crinoids)

 

Are the rock beds in the quarry face mostly:

a) horizontal
b) vertical
c) dipping in various directions
d) all sloping to the north

 

What is the name for layers of clay formed from volcanic ash?

a) Bentonites
b) Trilobites
c) Meteorites
d0 Muscovites

 

Select from the picture the most likely order of events here over the past 480 million years.

A, B, C or D