Field trip descriptions use notions from the introduction to the Val d’Hérens geology where all basic notions on local geology are explained.

These field trips offer an initiation to landscape reading, in particular to what is found under the landforms in front of us. This recent geological relief (a few thousand years) was produced by the erosion of the glaciers. Supporting this, much older rocks are found, they take us for a trip back in time over hundreds of millions years (Ma). The problem on the field is to recognize what is related to the recent glaciations and what belongs to the older geological history. Glaciers have moved rocks all over the valleys, erratic blocks were displaced over tens or even hundreds of kilometers, and these blocks are now juxtaposed to rock outcrops.

The size of the erratic blocks (usually of meter size) allows to distinguish them from rock outcrops that extend over hundreds of meters.
The solution to these problems is found in the determination of the rocks in front of us, mainly if one has a geological map at hand and geological cross-sections that tell us what is supposed to be there. For example, if one is in the Tsaté nappe (made of calcschists, prasinites and serpentinite) and a block of gneiss is found, then it is obvious that the latter is an erratic block derived from the Dent-Blanche massif.
How to determine the rock types in front of us? It is a relatively long learning process depending on the rock type, but guidebooks can be bought or websites consulted, such as objectif roche (Adobe Flash required!). More general informations on earth's dynamics can be found on http://objectif-terre.unil.ch. And many documents on the Val d'Hérens (articles, pictures, data,...) are available on http://ebibalpin.unil.ch/.
Also the description of each stop of the field trip explains what type(s) of rocks are found there, and a integrated glossary defines various terms and rock types.