viewer
Here's a nice map app, showing all the soil types in Britain.

SE23 is a bit of a disappointment though.
The bedrock is all london clay - I thought our hill might have some sinister feature forcing its way up from the depths of hell, but apparently not.

The site does not specify what the superficial layers are - presumably more of the same - London clay.

The exceptions are the Perry Vale areas where the superficial layer is labelled 'HEAD' -CLAY, SILT, SAND AND GRAVEL, which might explain a mysterious patch of gravel I found in my garden.
I think it true that this head layer is mainly found in the lower areas of se23 except for a patch under the high lands of forest hill boys school.

The other exception is the bedrock of at the top of sydenham hill/elliot bank - this is a more recent layer of claygate - SAND, SILT AND CLAY. I do not think it right to say this layer is the reason for the hill, but it might be more correct to say the hill is the reason this layer did not get washed away so easily. I'm guessing!

It would be interesting to compare this to a local contour map, but I dont know of any online detailed contour maps.

How interesting - I didn't realize I lived on the slopes of the Claygate Ridge, the most recent deposit of London clay - see http://wapedia.mobi/en/Claygate_Ridge. Like Perryman, I have always wanted to find a detailed contour map of the area. It would be nice to know where, for example, there are or used to be (underground?) streams.

Try http://www.ordnancesurvey.co.uk/getamap.
Type in your postcode and you will be able to look at a small section of the 1:25,000 map of your area (if you click on the top plus circle)- not perfect but the contours are clear and at 10m intervals. Hope that may be of some use.

Thanks, Brian. I tried this link (or rather http://www.ordnancesurvey.co.uk/oswebsite/, to which it directed me) and it did indeed come up with a section of the 1:25000 OS map for the area, with contour lines. The trouble is, I found that on the scale available the contours were virtually impossible to trace in built-up areas, because they were obscured by the details of roads and buildings.

I've always wished there was a proper geographical atlas for (South) London, or our part thereof, which would show clearly (on separate maps, presumably) not just roads, but also railways, underground railways, political boundaries (including parliamentary constituencies and wards) contours, streams and rivers, sewers, water mains, geology, land use, flora and fauna, demographical data from the census (age, ethnic origin, income, ecomomic status etc). Anyone know of anything like this?

Have you asked father christmas?

Have you tried emailing the OS and asking them? They do build their maps up in layers, including contour layers.

thanks Theotherbrian, this is exactly what I was looking for.

For any old codgers like me/the visually impaired, I've adjusted the map to show the SE23 contours a little more clearly, at the expense of other details. (If you zoom in, obviously)
   

I'm not sure how well this corresponds to the geology map though.
There are some questionable very straight boundaries for the newer clay deposits, imo, so perhaps the survey is incomplete.

Glad to have been of some help. It looks good!