Soil is the outside layer of Earth. It is a made up of living organisms, gases, minerals, and organic matter. Knowing what elements are in the soil helps to work out where it came from and how it was made.

Deeper soil samples for the northern half of Ireland were collected by Geological Survey of Northern Ireland (2004-2006) and Geological Survey Ireland (2011-2019). 16,800 soil samples were taken from the top 35–50 cm of the soil, in areas such as meadows, fields, parks and pastures. They were sent to a lab to be tested for the chemicals that make up the soil. This was done using two different methods. Knowing the types of elements in the soil can point to where they came from, how the soils were made. pH and loss on ignition were also tested, which tells us how acid or basic the soils are, and the amount of organic carbon in the soil. The results from the tests were given as mg/kg (milligram per kilogram) or % (percent).

When we map the data, we can see the spread of elements across the country. This also allows us to map different soil types. Deeper topsoil is worth testing as it is more related to rock beneath than shallow topsoil. This gives us a better idea of how the soil is formed and if there are any useful minerals in the rocks below.

Shallow soil samples for the northern half of Ireland were collected by Geological Survey of Northern Ireland (2004-2006) and Geological Survey Ireland (2011-2019). 16,800 soil samples were taken from the top 5–20 cm of the soil, in areas such as meadows, fields, parks and pastures. They were sent to a lab to be tested for the chemicals that make up the soil. This was done using two different methods. Knowing the types of elements in the soil can point to where they came from, how the soils were made. pH and loss on ignition were also tested, which tells us how acid or basic the soils are, and the amount of organic carbon in the soil. The results from the tests were given as mg/kg (milligram per kilogram) or % (percent).

When we map the data, we can see the spread of elements across the country. This also allows us to map different soil types. Shallower topsoil is worth testing as it is good for showing us if any of the changes were caused by the actions of humans. It is also good for farming and the health of soil.

The sample locations are shown as points. Each point shows where the sample was collected and the results for that sample.

The data is also available as polygons or areas, which show the 2km-by-2km grid square around where the samples were taken. It also includes the number of samples that were taken in that square. The data contains the average value of each element for all soils samples taken within that grid square. Maps of the grid data use colour scales to show the different strengths of the elements.

The Tellus survey is a national airborne geophysical and ground geochemical mapping project managed by the Geological Survey Ireland in Ireland and by the Geological Survey of Northern Ireland in Northern Ireland.