*Update: Here is a link to the lesson on youtube:

Geological field observations – what is oldest?

During this lection you will learn about, how geological mapping is done based on geological principles. Also you will see how the geology can be observed in the field. This is taught by looking at the mountain Sátan in the Faroe Islands, where a sill and a dike cross-cut the same area. Also other examples from the archipelago will be shown.

Relevant Polarpedia words to look at before the webinar: Hiatus, Erosion, Stratigraphy, Relative age, Superposition, Horizontality, Continuity, Cross-cutting relationships, Dike and Sill.
This webinar is well suited for the younger students.