Building Blocks by Iain Stewart

Iain on the side of a dam

The threat from below

Man's relationships with the elements in our surroundings can be problematic - even poisonous - as Iain Stewart explains in good rock, bad rock .

Meet Iain Stewart

Bringing geology to people who didn't know they were interested in geology - meet Iain Stewart, former child actor and rock doctor.

Related programme

Journeys From The Centre Of The Earth

How the rocks of the Mediterranean have influenced the buildings of the area

Several hundred million years of moving plates, erupting volcanoes and shrinking seas had left their mark in the bedrock of the Mediterranean region. A wide variety of rocks, almost as many as the Earth itself has to offer, were scattered across the region. In time, Mediterranean peoples would find more and more uses for the resource they were standing on – pigments for art, metals for just about everything. But in the early days the rocks provided the most basic needs. As well as forming the very land that people lived on, the stones beneath their feet were the handiest materials to use as weapons to kill prey (or rivals) or make tools. Such was its importance as a raw material for human development that historians have named our earliest times after it – the Stone Age. The change from ‘Old’ Stone Age (Palaeolithic), to ‘Middle’ Stone Age (Mesolithic) and finally to the ‘New’ Stone Age (Neolithic) is largely the story of humankind’s growing sophistication in exploiting rocks. And it would be rocks that provided our ancestors with their first home.

Almost any rocks that people have on their doorstep will have been used for construction at one time or another. However, of the couple of thousand common types of rock, only a dozen or so are routinely used as building stone. Unsurprisingly, they are the ones that are strong and rigid enough to support free-standing structures and that can be exploited with the technology people have available at the time. But the properties of these rocks are not uniform, any more than the kind of building they are best suited to: they are characterised by the way in which they have been formed, which in turn dictates the way in which they can be used.

Some of the most distinctive monuments of the Mediterranean are shaped by the rocks that ancient cultures had under their feet. The triangular pyramids of Egypt are a testament to the ability of soft sediments to be squeezed into blocks of hard ‘sedimentary’ rock like limestones that can be easily stacked on top of each other. The result is the only wonder of the ancient world left standing – the Great Pyramids of Giza. The gleaming marble temples of the Classical Greeks are a legacy of how heat and pressure has fused limestones into decorative marbles that could support longer, slimmer columns needed for their fantastic rectangular monuments like the Parthenon in Athens. Finally, soft ash that was blasted out of Italian volcanoes gave the ancient Romans the magic ingredient to make a super DIY rock called concrete, which in turn allowed them to use lightweight building blocks in constructing awe-inspiring arches and domes that literally held up their empire. The magnificent centrepiece of Roman building ingenuity was the Pantheon.

The geology on the doorstep of the main Mediterranean empires had provided the raw rocks to construct their greatest monuments and build their cities.

Content last updated: 15/09/2004