So how do these underlying formations affect what we see above the surface? First, the nature of the soil also has a major impact on what flora [link to flora section when available] will do well. This applies not just to native flora, but to cultivated plants as well; the Lower Greensand has proved particularly good for orchards and fruit growing. This reached a peak in the mid twentiety century, and a map of the distribution of orchards at this time corresponds remarkably closely with the area of Greensand.
The local geology also has a profound impace on traditional building materials. On some parts of the Greensand - particularly near Sandringham and Gamlingay - a low quality, golden-brown stone known as 'car stone' is found; this is rarely seen in Cottenham, but there are some pieces in the walls of the church. A direct result of the lack of good local stone (stone for the church had to be shipped from Barnack near Stamford) is the widespread use of locally made buff brick, which gives a distinctive appearance to the majority of the village's buildings. A lack of iron in the local Kimmeridge Clay made it easier to produce these creamy bricks, but the shade of buff obtained is subtly different from that of the 'white'; gault clay bricks of Cambridge, and is sometimes tinged with red (owing to impurities and differences in firing temperature).
Although Cottenham is hardly rich in mineral wealth, man has exploited what lies underneath the soil, and this continues to leave a mark. Digging for gravel, particularly in the north east of the parish, has left some substantial pits; now filled with water and often a haven for wildlife. There are also claypits on the north west edge of the village. More recently and area in the north east has been identified as suitable for landfill, resulting in the accidental creation of a new wetland habitat and the deliberate creation of a manmade hill, growing tall on the rubbish of Cambridgeshire as I write.
In some ways, however, the shape of the land is at lest as important as what it is made of. The position of Cottenham on the edge of a large flat area with poor drainage is probably the single most important factor in shaping its landscape. As we shall see, relatively small changes in sea level could drastically affect the natural vegetation. The formation of marshy fenland in the middle ages determined what types of agriculture could be practiced, and hence how man treated the landscape; arable crops could only be grown on the Greensand ridge where they would not flood, while the deeper areas of fen were only suitable for summer grazing. People also needed to live where it would not flood, and even with today's effective drainage networks there are remarkably still few dwellings in the fenland parts of the parish.