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We're not talking about music here - have you ever stopped to think about what is underneath our city?

Today we are surrounded by Victorian architecture and modern developments, but Leeds is built on rocks that are over 300 million years old.

A closer look at the geology of our area can help us to imagine what Leeds looked like in the distant past.

The rocks under most of the area immediately north of Leeds (around Otley) are the oldest and are the sandstones and shales of the Millstone Grit.

These rocks were laid down during the Namurian Epoch (323-313 million years ago) at a time when a huge river delta extended across much of northern England, including our area.

Rivers flowing from high ground to the north created the delta where they flowed into a shallow sea and deposited sand and mud. This was eventually converted into rock through burial and compaction.

Did you know that 310 million years ago the area that was to eventually become Great Britain lay across the equator? The great delta that had been built in northern England in Millstone Grit times was now largely covered by plants which grew rapidly in the hot, wet conditions.

The forests teemed with insect life (including giant dragonflies with a similar wingspan to a magpie) and the rivers and swamps were populated by fish, bivalves and large amphibians. Dying plants fell into stagnant water where they accumulated to form thick layers of peat.

Large areas of the forest were repeatedly flooded by the sea or rivers, forming vast lagoons and lakes. The peat layers were covered with mud and sand and over the years the weight of this compressed the peat into coal.

The city of Leeds is built mainly on these Coal Measures, and in the 19th and early 20th centuries coal mines were a familiar feature of the skyline of south Leeds.

Around Wetherby there is a narrow strip of younger rocks (from the Permian Period, 290 - 251 million years ago). This is mostly Magnesian Limestone which, due to its gentle easterly dip and greater resistance to erosion than the rocks it rests on, forms a low, north-south ridge to the east of Leeds.

In addition, the Wharfe and Aire river valleys both show signs of glaciers moving through them during ice ages which have occured over the past two million years or so.

As the ice sheets and glaciers retreated they left behind the rocks and debris that they had carried. This material, called till, is still soft and consists of sticky clay containing boulders and pebbles.