The Lickey Hills are made up of five main rock types. A walking route, taking approximately an hour and a half to complete, will take in all five types.
1. Barnt Green volcanic rock
This is one of the oldest rocks in the Midlands. Although it’s not visible in the park, there are some small exposures to the south of Cofton Hill.
Although Pre-Cambrian in age, they are not much older than the Lickey quartzite which sits on top of them.
When seen, the rocks are purple, brown or green, fine grained and hard. This rock originated as volcanic dust which covered the ground forming a hard rock as it compacted.
2. Lickey Quartzite
This makes up the whole of the Lickey ridge, running from Rubery in the north to Cofton Hill in the south. It is Cambrian (570 million years old) in age and unlike most quartzites it is a sedimentary, rather than metamorphic, rock. This means that the sand grains from which it is composed have not quite fused together. Examples of the rock, which is sandy or glossy in texture and buff or pink in colour, can be found all along the ridge.
Towards the northern end of Bilberry Hill are some darker boulders of quartzite, which display evidence of 'bedding'. A better example of this bedding can be seen on top of the steps at the end of Bilberry Hill. The rock was formed by sand being deposited at the bottom of a shallow sea. The sand grains were then cemented together by silica brought in by circulating ground water.
3. Keele Clay
Follow the steps down the side of the Lickey Gorge, cross the road and follow the main path to the right of the golf shop up the slope towards Beacon Hill.
In places, the passage of thousands of visitors has eroded the grass and soil to reveal a reddish clay deposit, the Keele Clays. This muddy clay deposit is Carboniferous (345 million years old) in age and is interspersed with occasional thin beds of sandstone which are seen as small banks out on the golf course. The clay was deposited as mud on the floor of a shallow lake surrounded by a flat semi-arid landscape. The sandstone beds were formed by periods of increased rainfall which carried the sand, mixed with clay, into the lake and were then deposited on the lake bed.
4. Clent Breccia
Carry on up the slope to the main path junction. Turn left and follow the large path round to the right up slope. As the gradient becomes steeper, the rock changes from clay to Clent Breccia although the rock is best seen on the left when the path levels out.
The breccia is compacted gravel, consisting of reddish angular rock fragments surrounded by large amounts of muddy rock. This is Permian (280 million years old) in age and was formed as a flash flood deposit laid down in a hot desert by short lived torrential streams. The angular natures of the fragments show they have not been carried far.
5. Bunter Pebble Beds
Continuing along the main path leads eventually to Monument Lane. Turn left and walk down the lane to the Monument (constructed using Anglesey marble). Within the monument grounds, the rock type changes again. Where the vegetation has been eroded, the bunter pebble beds can be seen. Triassic in age (225 million years old) these beds consist of rounded water worn pebbles and make up most of Lickey Warren. They were deposited by a powerful river and formed part of a large inland delta that once extended from south of Worcester to north of Stoke.
Leaving the Monument on the Old Birmingham Road, turn left back towards the top of Rose Hill.
6. The Lickey Gorge
It has been suggested that the Lickey Gorge was eroded by glacial melt waters. It is speculated that a large glacial lake covered the ground to the west and when the ice cap started to retreat, the melt water escaped over the dip in the Lickey Ridge and once this spillway was established, rapid downward erosion followed.