![Top curves](../../../../jsp/jahia/templates/GSL/gsl_templates/img/keystage3/main_top_grad.gif)
Limestone reef, Derbyshire
This limestone cliff shown at the base of this page is made up of the remains of corals, crinoids and shells that formed a reef within a tropical lagoon that covered much of the Peak District around 325 million years ago.
Thinner layers of limestone, formed as carbonate mud, surround and cover the hump-like reef structure that now forms a cliff above the river Derwent, and is popular
![Limestone reef fossils](../../../../webdav/site/GSL/shared/images/education_and_careers/RockCycle/RocksAroundBritain/Lmst%20reef%20Derbyshire.jpg)
High Tor, Matlock Bath, Derbyshire
![Derrick Clements, www.heathbank.co.uk](../../../../webdav/site/GSL/shared/images/education_and_careers/RockCycle/RocksAroundBritain/HighTorMatlockBath%20xtrawide.jpg)
Derrick Clements, www.heathbank.co.uk
![Bottom curves](../../../../jsp/jahia/templates/GSL/gsl_templates/img/keystage3/bottom_curve.gif)