About sousmonsol

sousmonsol brings together on one map the public data on the ground beneath France: geology, groundwater, clays, cavities, earthquakes, quarries and mines, in mainland France and overseas.

How to use it

1. Search for an address, a commune, a cadastral parcel, a borehole or coordinates; or for a theme, a layer or a legend class (“granites”).
2. Show layers in one go with the themes, or one by one from the catalogue. On layers with classes (rocks, clays, seismic zoning, radon, flood prevention plans…), “Filter” keeps only the ones you tick.
3. Click on the map: the “Beneath this point” summary sums up what the data says at that spot, and the detail sheets describe the layers on display.
4. Share the link: it restores the view, the layers and the point.

What the “Beneath this point” summary tells you

Shrink-swell clays

Clay soils swell when they get wet and shrink when they dry out. These movements crack buildings with shallow foundations. The BRGM map rates the exposure as low, medium or high.

Rising groundwater

When a groundwater table rises close to the surface, it can overflow or flood cellars. The map shows the areas where this may happen, and how reliable the estimate is at that spot.

Cavities and ground movements

Underground quarries, marl pits, cellars, landslides or collapses: the summary counts those recorded within 500 metres of the point. No record does not prove there is no cavity.

Earthquakes

The maximum intensity possibly felt in the commune, estimated from the historical earthquakes of the SisFrance database, on the MSK 64 scale (I to XII).

Nature of the ground

The rock family according to the 1:1,000,000 lithological map, and the sheet of the 1:50,000 geological map that describes the area in detail.

Its limits

These maps are drawn up at a given scale, from the knowledge available: at the scale of a single plot, they show a trend, not a diagnosis. They do not replace a geotechnical survey, the official risk statement provided when a property is sold or let in France, or risk prevention plans.

Where the data comes from, and on what terms it may be reused: data sources.

Working together

Enjoying our work and this map viewer? Would you like to bring it into your company, or show your own data on it? Let’s talk.